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Title PRINCIPLES OF HIGH TEMPERATURE CHEMISTRY
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Author Broker, Leo.
Publication Date 1963-06-01
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Ernest 0. lawrence Radiation Laboratory
PRINCIPLES OF HIGH TEMPERATURE CHEMISTRY
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, r~:~~~;:;;-,e e~.:;:f Robert -~::--1 ! '• · Welsh Foundation Con(•. , ~ousto~; :·UCRL-10619. . . 'i •. . . . fl Texas ~ Nov~ 26, 1962 (and to ft be published in the Proceedings)~ ··;.._ ·.~lm ,. ,· .. ' ; - •'· j ~ t•l ' '• II ...... , .:· .. : ,, ' .. '';:' •t., ·-.~ -~ .-~ ~- ·J -" ,. ,. f ,• ;,.· . j ; ~ ,•.,c·::·.. · ~-· ~.' ,. ' j, :. ; '~~'I :. ' ~: .. ·, ·{ ;" :. . ; ;UNIVERSITY .OF CALIFORNIA . \ .• . ·, -::~ ( ,. l'. ' ~-) . ~ ~ ,· ' .... L~wrence .·Radiation Laboratory i. . . "l :'io' ·.Berkeley,. California . ~ ~ ' ,, ,· j ,. 't'" C6ntrad't No. ·w ~7405 ~eng-4S · - -~- -:·. . .? . \ ''·;'· . ~ i} _::( : . . ~.; .. ,. . ~ . ·, .... :_j~ ~\ ~ ...... 'I ·, . ·'•t ' ' -~ ..; . :_(. ' '·,' t·. -~·j! •. ~ ;. : ) ~~ '',. . ~ .. '.·· .~.· •.!.-i l, J_ ~
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: ~ .i ·.. ··~ • ' .·j .•'' J· . i ·~: . < ·., '· . . .~ ' ( PRINC"t:PLES •oF HIGH TEMPERATURE. CHEMIS1',RY · i·. ,. ·-:: -~ ' ·.. -·~·· ·.~· \ 1_.: _, :.· ~--·. . .'· ~t .. ; i,.j'• 't· ' .: i,· ·;,, ;·· .. ' ;· • ' ...~ .':. • "•-"f~ . \. h ~ June 1963 ~--.. j: !.
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·.' } ;, -1- UCRL..,l0619 . . . ;. ;; .. i ·. ' ( " : (-' •; PRI:DTCIPLES OF EIGH .TElv!PERAT"URE CHEMISTRY
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; ' ·.·: ."i .....l ...... ·~ ~ • ~- ...... ___ -1.,..:..... •• ~-- •. t. i. ,. ' . . ' I ,. ' . ~ ,. ' · · Department of Chemistry, and Inorganic V~terials Research Division '' of the Lawrence Radiation Laboratory, University of California·~ ,, ,'..., . ~ Berkeley, California
;: . . , . .... ------. ·- ... ., .... ·~ .. -· ·-··--··· ··- ...... ·-·:--··-·----~----·-· .. ·--·------__..,-·------·-··-··-· 7nank you, Glenn.
'It is a real pleasure to be here in Houston today and to participate
. in this Conference.· , I . ' '' The developments in high temperature chemistry have been much too . .; ·extensive to hope to present a complete revie~or of this field this after
', noon. ~lhat I propose to do instead is to present two thin cross-sections
of' the field. Fir-st I ~orish to take a cross-section in breadth to examne
.... so~e of the general principles which characterize chemical behavior at
, high temperature, and, in fact, disting~ish it from the normal type of
··chemistry to 't·rhich we are accustomed. Then I 11ould like to take a cross-
section in depth. by taking one particular relatively :r4rroi-l' field and
' ' ' carrying ·it throuen to the present frontiers. In this manner I hope to·.
. point out tr.e n:.ajor problems· of high temperature che~stcy' and to indicate
·fi.. I I ':: "--...... ·' :. , . so:x.e of· the tecbnig:,ues th8. t are· needed to resolve these problems. ,,.· . '' • !• r, ···;: Often 11hen I encoUnter people i-l'hO are not famili~r i-l'ith high te:znporature · . '' '•_!.
.. ' ,., ·cne:nistry, the usUa.l comrn.ent is,:. "Oh,· it must be very· :difficult to produce . }: .· ' :: . · ; · t:nese hiz,."l. temperatures, but,·.'~t least once you get them, the cltell).istry ,1,' '"' . 1 -, ' < must be verysimple~"·o:r course, it's. just the opposite •. It is very ·' ) .easy to get high teni.peratures., but high tempera"~U:re chemis-try can be ', ' . ·.' ' .... :. •, .·. . ·. ,-:-' .. ; .. ·: ' . ' . . e:ftremely complex/ The :f'act that rat.her complex ga.seo~s mOlecules 'eXist . ~ . . ~ :· . .· • •, I. .' in high temperature· systems and that the complexity o:f' saturated vapors
'··
.' ·! 1.
; . ::: -2- ~. (, ..
· i·rith respect to the number of different species actually .increas.es vrith :· ',.~· ' : '. increasing temperature seems to pose a paradox to most people. ~lhat I
.<~ ' i·Iould like to do is to present some simple thermodynamic reasoning to " '. resolve this paradox. and to illustrate l·rhy it is that high temperature .. :; • chemistry is so complex, and essentially establish some of the'basic
i' principles which fix the chemical behavio~ at high temperatures.
' Now, to simplify _our discussion I 't·Tould like to l;"estrict my examples·. to a specific type of problem. I would like to discuss the problem of
equilibriumbetweeri a condensed phase and·a gaseous phase athiBh temperatures. ··. . • •..... i,,2 3/" . Actu·a-lly ali. of the co:rnments I will make can be generalized '\_ ~, · to a ivide . . . . . ·,;:.. range of situations, e.g., completely·condensed systems and a variety of
; . ' other systenis. I thin.'1): it might simplify the discussion· if YTe just restrict
. .i ourselves to a specific situation .
I think Ylhat misleads most people ivhen they expect chemical behavior
in high temperature g~seous systems to be simple is that they are thinking
in terms·of heatinga gas·at constant pressure in an inert container. ~{hen one heat~-\~terials one most. always has t6 contain the gases in some t:rpe of material and there is thus almost alvmys a condensed phase present .
., ' . ·' l' W".nen one heats a gaseous system in contact uith a cond~nsedphase the
partial pressures of the various species i·!ill not ·remain constant. · And
·. as•·r i\-'ill ·shmv. shortly the _pressures· t;,.ill increase fa~t enough to offset. ·· .. ·.. f . ·.any simplifying effect of increase in temperature that might be expected .. ";· !,.··, ' . . . ., . . ' ' .
· -in 1 a· system at constant pressure; so that, in fa~t, high temperature ' ...... ·~· . ·' . . g~se'ous systems in contact with condensed phases \·rill :become more complex .
l ~ . :.. ~ the higher the temperature.· ·.. . ' ., : . !' ·•' f ) .. . . . :, . ·.;.. High ·temperature syste~ become· more . comptex in three principal WJ.ys.
. ,· First, the oxidation numbers and formulas of the_ compoUnds become unfamiliar . . ; .. ; '
-3- 'r
at high. tem,Peratures. \·le are accustomed to the alkali· metals having an. ~:~'\. .... ' :'i.-. . ' oxid?-tion number.of 1,· the alkaline ,earth metals having an .. oxidation number
of 2, aluminum and the third group' elements having anoxidation number .of ~~-: 3, and any deviations from those oxidation numbers at room temperature
··would be considered quite unusual. At high. temperatures these arc no"c the -~- co:mrnon oxidation states at all. One finds a variety of unusual oxidation ·states. Compound~ lilte LiO, for example·, are quite. stable and compounds· ~ . ' \,t;;l' of bariuni< in both the l and 3 oxidation sta<:;es are observed. Alur.a.inum
,. ~ t occuri'P-!J>'i~ the. l and 2 oxidation state~. At high temperatures one can ·:
. ' ' just forget about the octet rule and all the other valence. rules that ".·le .
have been taught. Anything goes. That's the first complication that
a:dses. You won't recognize some of the compounds you will see listed·
in the figures or some of the compounds I idll talk about if you are ·' ·' accustomed to thinlting of chemistry at room temperatures. We •rill discuss ·. ,'·t in a moment why that might be.
·.The second respect in which. gaseous sJrstems become more· complex at
' ' · high temperatur:es ~s that the molecules becom,e very complex. There are
·I no.t only diatomic and .. triatomic molecules but also gaSeous molecules w·ith 5, · .!..·.:
10, and more atoms per molecule . . 1 ,i The third vray in w·hich these gaseous systems become more complex is '' . :·.! , , : tp.at, in ~ontrast to low temperature systems ".-There one ;maY hive one .or
• ' ' • • • j • ". two principal spec·ies, one may have many different species of roughly.
' '
·•· :-co~parable' importance. . . at high temperatures~. '' :: .. ,.j Now, •.I · vrouid ·like •to •exUmine some s:p~cific systems. Fig~ ,·.··. ,. In 1, I have.· '.' _jU:st put dmm .a few· examples of molecules •·rhich have been found to be . ;~ i ·. ,:1?. . • l I : :·,, .. · .· l ·... '''
i~portant. . ..in ,· b,igh temperature'gaseous...... systems.. . You. se.e .,that these ~re CJ.Uite ·
~· ',,· established by use. of the mass action lavl and in recent years .a very la::-ee
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.. :. r .., •. ~' 1 . \ •. { · :· number of ne~1 .species have b¢~n .dete.cted by' use of. the ~ss.·sp~ct~omcteV ; ··- ··.:Perhaps some of y~u have 'seen the note that.Paul G:n{e)-t9·
':;:varyin.;{sulfur to bo.ron ratios and molecules with the total nu1nber of atoms .· ... ' 1 . ··'. :' i:per molecule. extending to t'l·renty~ thirty;· or perhap~ ~ore'. 'l'his is typical. . : .'· l. } ' of satu=cated gaseous systems at high temperatures~ .!~here are a lot of
...... dif.ferent species; there are species vtith many atoms· ;pe:r molecule;· and there ··.•. .. : . ·· .. are unusual oxidation states; :,:. •. :' ·.· ..· . ._· . . : . ' This is customarily very bcl·iildering to persons 'lvho have not bce.n·
familiar l?ith these facts and it Hould appear at fit~t glance that. ~: .' j ;, . chemical experience at room tcmpe1~ature ·is of no value in predicting h~gh •" ',. · .
. /".~... -~ ·-~:··· . \~o shmr that high temperature behavior can be related to the overall : ,l ~ .· ;\ i;<·. '. i.mderstanding of the .behavior of materials at all temperatures: · Fie;ure 2 · ,·, i .I ·.,_ . •: 'I :· :;; . ' ' ' ' shm !·'. :'·1 J•'• .The tree energy; change determ:i_nes .1.;hether a rea~tion 1-rill 'c;o or not. 1.): standard free energy change o:{ a·. i•eaction determines the C).~tent to ' :~ . (; ;' ' ~t~rhich the. reaction 'will proceed under. eg,uilibriu.rn conditions. .R.:.ck in· the ; ; . . . . I . . . \J.&! . . , l .· :• i;p,ays: of Be~thelo1'{.1 and Thomsen'-! :L"C ·Has believed thdt the hco.~c of the. : : . ~ ! . ' ' ' .'; . . . ' . . . . :-!' ·. j '. , reaction was the; primary facto~ ,;hich determined i.;hether. 'o-:: not a reaction ·. \ . f I As· thermodynamics • developed· it 1-1as realized that the important ... ;,, '\ ;! .·· I ' ., ,\ .' ~' ; ' ·.... : ,J ', ., ' ,:· . ~ ·. . ,,; '," .... ,;• ' ' I ~. ,: ·. ;t .. ~ . ' t. ·, . , :· j··r . i .1 ' (· ··: R .. ,1' i· rfi ...... , ...... -~·· c· .... 1... ~.; ... :.~,...,;:... ,rn ....1 ~,,r',· c -,...~..~, "'"':·1-.~•u--.-·.~.:-1 ·~ i~~-.!. B ~~.!,. . I,., ,.?....:.;.~ ~t,.;.~•.• h ..~.) J..~o; •• • """ ._.J....C;;, v..;.. · !:..:....·'_ .. .. J.:'t.J · \ ':- ,.' ,'i .. .; . 0 ·.!.Eo f:::.7:' ., -'.. ,·, so T . ..) •I i = ~-" ":: c ·' ·o & !ii:"p~ ..; ... R l11K /:· -m:- tsP - .l- s: .... : < ,. 1- I ' \f ! I : j ,. ' ' .. ! ·:'I - •• :<; .-····· .. ' : 1 .;;_ .. . < ··. .' ·• l' ·'·.. ; r .i ' ., ·-:.; .... - :~ ~ t 'ii ' . '· ,. .. 1· -~ ' v ' ! ! '•.f, ·" i . ~ ..r ; ..... ' ' ' ··., >"" :: . ... ;' ·' : -~ ."::· ., ·.(_ ' ,,• -~ .' ' ' ) _,; '.·.· '' '',. . t -5-:. ) : ,• •'I . ~ . 'l'' •' • '. ~ r ' :1 .. '; l· '· '. ii'actor was. the combination ~f heat: ~net entropy or t~e· 'fre~ energy vlhich : ·~ ' · , :, ;:,;·determined the 'equilibriur.i constant as, ~hm·r~ on the 'slide. Customarily . . " . -~ ~. . '. '' ~. : ( 't. 1 t ·~ ::~,'at room temperatur~ ,. exce~t' for': some: unusual aqueous' reactions,'' the .. ,. 0 ..• & ) usually a SDlall correction term. ' The •, ·,:;::',•~,difference bet,·T~en ~: ~d ·~~· i~ ,j ,< ' in :.· . . : :~o usually will not be decisive deter::r.ining vlhether the reaction .. ·._j4 . ' .-.-· : 1 ,··\,ill go or ,t10t So normally ,.,e. are accustomed to reactions· proceeding '. .. .'! :,, ·' · i:t' they are exothermic and not .Proceedin'g if they.ar~; endothermic . ~ .1, ~: . .·· ...... ' 0 .. . -~-. .. ; ., It is, the .6.11 -vrhich is of prime importance at ordinary temperatures . .i .·· : ... . · ~ . ·. . . ·.. 0 ·. .., ·:~At high temperatu.res the order .. .'of importance of the two terms, .6.H arid · . ·:. ·j ·; L 0 . . .· , · L:S, changes ... This is best seen in the. second equation of Fig •. 2 vhere '. .. :;the .standard free energy change for a reaction i~ related to .the eg_uilillrii.un '• .· constant. For·an eCJ:uili1:>rium constant to be large, that .is, for the .. . ' . reaction to proceed in the direction ·in "i·lhich it is vlritten, the standard . , ,., . 0 .. ·.' . . . , '. ·.. :tree7"energy change has to be negative. 1·T..1.en TtS is small at room. terapera- . . ·. ''· .-. 0 tures, ·it ·is. the .b.lf ·term .•rhich will nor~lly detennine the sign of & . ·If the relative importance of the heat and entropy ternis is re-exrunined "/:•; -~ ·-····: '( '. ·'. ·.,as the temperature is in~reased from 300°K to 3000°K,: :for. example,· it is ! . . .. : . ··: . ' \.· . . :seen that ~· becomes increasingly less important in determining the sign 0 ;~f t:::F and the value of the equilibrium constant. Obviously a'c a high ·,.f .. , .. •,; -~ .·.; ·::enough temperature 'it is the entropy term which becomes the primary. . r ) '! ..· ·' ' factor in determining 1-1hether reactions i-1111 go or not. ; ' ··t ! 't' ' ) ... i· !.': '. 1 . ~ -. i Tha.tessentiq.lly·is the basic reason for the drastically different ~ . ' ; . i: •. J; ~ . . ·behavior that one ·finds· in higp .tem:Pe:rature systems' c~mpar~d to' lm-1 · ',·; .,..· .. ~ . ' '. . I ~ ·.. temperature systems. · In lo~r temperature systems the 'stable rn.cil~culesare ~- t ~ . ~ ·; ~ ' ';those that :i·le· are accustomed t.C> thinking of as being ~~turated,' those t!J.at . i . . { ,.. !' ., ,-·s'atisfy the octet rule.'. They give off the 8~eatest a::nount' of heat . But • • • ~ • ,- • ' ' I '_- ~ . ;.: hi""" 'it is not so important to heat .. of' ~t.· 0"-" _t~li.~eratur~s~./:' g~t, th~lmost·. ·'I ou~~ the reaction. . The more important question is hmr much did the ·entropy ':.,. '·'' '.,· .· ~ . ' ' -6- . ' ! ; l! . :increase? . So we are not going to care at high temperatures w·hether we ... , ' .. ~ . \<:··get the most stable bonds or wheth~r we satisfy the ocW:t:: rule or any : \ . . . ' . . . .. ' . . . . 'of the other 'ruJ,.es which determine 'the heat· evolution> It turns out that. ' : ;, I : • • ~ • ·.. : l ; . \ ihe reaction which. gives the most t:avorable entr()PY. change' need~ not be one :.-· ' ..: l . : ~ .'· . . ' . l ; ' ___ :· .'. . .· ;,. . . . ; '';which will involve a ·familiar· oxidation number and orie .. can observe a variety . . ' f,, ; j j :.'of oxidation':~ta~es:of a given element. ' . . ·::: .. .'• ..,.: .: { . ··' l ·. ··. i . Now; ;we.'can examine this problem iri a little .mo~e 'detail and to .ao· so· ·.) •' ::" .; ' ~ •" '.; ~· •' r .' \, . , · ! : . 1 ··:,I would like again to're~trict myself to a rather s:i,mple exampl~ which can ;.\ ' ·. '. ::~be e,asiJ.Y ~eneraliz~~~Yto. <3.rly t~e· of ·reaction. ·~nat· I would like to ·:.,. ·.r .. ·, . : . , .. · . ( r. . ·. . ·'' . . ; .. . ·': .. :·>:.~ .::.:~onsider ·in Fig•; 3 .is tlie, vaporization of some mater~~ ·to two possible ; , . i !:(spe~ies.- One is the monomer which is. designa:ted. here ;as A. and the othe~ is the ..• . J· ... '.: . :·,t . ' . ·dimer which is designated. as A . :For. one mole. of .liq~id ~apor~zin~ to. the 2 :.: .::::: ~onome~~ the :heat 'of vaporization•of the monomer is d~signated by L:JI . For : :; : ~. I • . ' • . • . ' ' " ' 1 . •: two moles ?:fliquid A going to the dimer} we have ~~ the' heat of vaporiza- .. - ~ ' i • ; .. , . .. \ .. :;tion of: th~' dimer ... . ~ -: . ;. ' '. . J ; :. · : ; .. ;: ; .In the gaseous phase there must be an equilibriUm between the. diiner. ond !~ ; . ·. ;. ,· ·; the monomer .imd th~ enthalpy Change Of the diBSOCiati6ri .reaction is given by .j" . . ·j '; ., . . .:AR_. . I !,• Fo:r the:.pro~ess of removing 2 moles of r.1onomer. direc:tly from the liquid, ·' ;···~lJ .'· . ' •· the amount of heat .required will be 2 times the heat ~f vaporization of. the '• ' ~ .monomer . If we :P;i:-odu.ce 2 moles of monomer by the two-step process, .fir~t .... ' ·: f. .. . 1: '.· .. · . :vaporizing' 'a mole. of dime.r with absorption of the heat ~} and.then disso '·, :-...... ' • i . ~' ;/iating the dJ.mer to.,two monomers} .we must add the adC!-itional heat, &~'. and ':·; -~ ' .. . ·{ .. • '\ie obtain the final::identity of' Fig.' 3 showing .the ·reiationship betHeen ' ,. '· .~ . . . . .' . 1 \ ' ' ; . , :the heats of vaporization of the monomer and diiner an~ th~ diss~ciation, energy ·: ? . • l > ..._.·.. ;:, , . .·'of· the dimer. ; i· i. ' . I have presented this particular example to .. minimize ·,: : ·, \ ' : -ba- ,. ., ··! ... ~: ,. '\ ; ' '· / ' : Vo.pori za tiO~l. e' CJ.Ud. tions for ~ Tj I • •' ! ;.. . '\ • . \ \ f i ·,I . ' ~ .... . : " ' ·_.·'. ' ; .,, I. ... .( \ ' t ~ : ' ·' . •, · •, ir '· !· ' . ~ 1 . ... ~ ·, ~ ' .. '• .· ... ~ ' .. ~ : ...... ' :! . i r. ' '.,, . . '·' '· .... !; ' : ·.•. . ·! 'I : .. ' ' ·. ~ " ,., .~~ l f·• ::.. t. "' . : (. ·, ·,. ··: ..'t '; . ). ; ~ . J ; -~·. ,.'· •,•1 ,; ,,. ,i ·"'· ...... 't .,' ..... · :f. f.; .' ~ : ... .. , '· ··· .... · / . :: :y '/' ... : ') 'i r. i !' r :. 'f : . .. .i ' . .:.: .:. I '•t -,,, ' .~ ;_7- .. ._} (' . ; · ... :spould be· approximately the same as the order of the heats' of vaporization .. If one 'of these heats, say Lili t:s then the standard 1 s!llallerthan:·~, . ~ . ·. ,ll '• I r·· ~ . . ···I . / - ~ ; . · ?-~mer and the partial. pressure of the monomer will be ·larger. ; , .. . •' ... Now~ I would 'like to consider two possible situations·, one a situation ·,; t <' l ' . ., ; ' I where the dimer. is the most important~ at low temperatures vrhen we have ''' . equilibrium between the .condensed phase and the vapor·.:.· This corresponds to . ~--.' ! ·· a: very sta.'ble.dimer, that is, liliTI ·is very large. It 'takes' a lot of heat to ,,. disrupt the dimer to monomers. Now, you can see from the pottom equation of '; .; :.:·, F~g. 3 that if~ 'is very large, then~ is going to be small compared to ; ·,-; ' i . ' ' . · So is very large the heat of vaporization of the ·dimer Hill · : _.6JI 1 ~Vhen &~ :, ~ ·. \ be smaller than that of the monomer and tb.e free energy of: vaporization -of · . ~- .. .'. ·: ~- ' the dimer 1-rill be smaller than that of the monomer and -the' vapor vill be.· ' . .· ·.· . '14/ ·. t-. ~--. i predominately dimer. Aluminum trichloride would be an example>:":,/ I · .. ' .. ' ~ ; ' :I ; .' ~ . ; ' _; ' - : The above e~ample is not the usual situation.. The usual situation is , . ; ·,qne where th~>heat· of dimerizatio;n or;the liliTI requir~ci'_ to dissociate the . ~ 1 .. . ·r: . /·', • ·. ·: ' •· ..· , '· . ' . . ' .. _. ., ·. •, .. ' ,'t1 •' , : ;-~imer is smal~ compared to the energy required to pull a monomer out of·the ' -·· i . ! . . ; :: 'condensed pha~e: : veri frequently ,ther-e are many bonds; that have to be. •r. . - ·. ·_.:. . . . . ' ' :'b:roken wheri' a ;monomer ,is pulled out of the condens~d :phase i comp~red to perhaps '·;· t ·.- '·'- • :.:. orily one bonci t; be: brokeh dimer' is broken .into monomer.s .. . t.' ~hell ~he •'i. i : _;.. ', t ~ ; ' ·, ' ; ; . ; ·' - ., . " :;·.: i ' .. ''; 'i . . ·-:: ~ "' .. :~ -~ ' ' "· . -: ' ':• .. :.: ~. ~ " - \ ' . • • • • l /, ~ ;·, ' . ( ' • . ' : '. ', ;_ 1_. . . ,,. ' I -1 . 'j . , ; ~ i. ~ : :· '' ' ; . -~ ' . f • 1 ,· ~8- '··: ''· t .,, . f-1 . ~ Hhen that is so and. AHn is small compared to ~he heats of vaporization, '. r: ~ . .. .. : '·' ' ' ~hen must .be large compared to .6H Conunonly thet saturated vapor in .cJ32 1 . e~uiiibrium with a liguid at room temperatures will b~; pred.omin~tely .ir .· ; • j_ ... .;. ·' monomeric. ·· .. There' will be a. much sma'.ller p.roportion of' dimer. Such a situation ::~ is illustrated in Fig. 4. The· monomer vrill have a higher partia,l pressure .. '. ' .'> i because it has a lower heat of vaporization. The dimer will have a lmrer . . . . . :partial :pressure because it has ,a, higher heat of vaporization, but for that : i. . .: same reason, the dimer partial :pressure has a much higher :temperature coeffi cient. The species which is present at lowest partial: pressure has the ; .: highest heat of vaporization and must increase the more rapidly of the tHo. T'nerefore the dimer must gain on the monomer and the higher the temperature of the saturated vapor, the more comparable the dimer' and the niononier become. ,, ; Actually this can be easily gen~rali'ze~.. /'\o trimers·; to disproportion~ ation' ' reactions, ·ionization reactions; and any sort of: vaporization reaction . . This generalization can be made: The· species which 'predominates at 10\.r · · · ·.temperatures, and 'normally there ~ill, be one species 1-rhich· '..rill predominate ' '\ ' \. i: ~ :: at lo'W temperatures' over all the other possible speciep, i·till generally have ; ' l. ·.~ O:the lowest heat of vaporization and all the other species i·thich are relatively . '' :' ~· ; . · W."limportant ·at low temperatures will have higher heats, of vaporization. · There- :. ~ . ( I: . ·.fore, the multitude of all these other species th.at are unimportant at low· . ' t ,I ~ . ~ '•, · ~_. -.-~emperatures_ must· gain. more rapidly than :~he primary speci'es as :\Ye increase.; ' '~ . , . ~ ·. ; '{ .. " . ~he temperature in the saturated vapor. This means that the higher the · !.:, ·''· ~ .. ; : . temperature the more complex the vapor becomes with 're~pect to the number of i' ...... different spe'cies of ~omparable :impor:tance·, and at the. very highest saturation .·' ~·· ...... -- ,. : temperature; the criti,Gal:temperature, ;one has a very large';collection of ; .'·! L 1. ... ''· . ' ~ . ._,' . • speCies of all typ~s:. ·:: •, -:. :<.! . t: ' ,._ l·- . t. : \ ., '·. ~ ~- l ' .) .... I '(,· -Sa-, I I . .. ··,· '•\ ; .... ,:.: •' .; ~ •'· ·. ,. ~-" ' ...... ;.j >' .~ . ..·: ,, ,,' ',• . : ~, i . -~ 'f• •' !:'-· <, .-! ,. 'L\'\ ,,, 0) ; rl ,•;' :1: j,. ',·' ., ·. '•, ,,, :-·- ,,,.. • ! ...... :~. >, ' . :.~ . ' ~- ·,f ' ' . . . . ,, ... ~ .. l j ,, ·,, , ' \ d .. ,·",' :~- .. ,, .\ ! :'.; n : 1·,-~::> ' ~·,, ,, )' _; ~' ' i. ' -~ !, • .. , . :r,., ·, ~- _.,, I' ,, ,(, .' ·~ r·:l ,, ,_, ' ;: ' .•lj'' ' ~~ I ~ ' t . . _;;; ~ . i '; ' , ' i; C::J~- X: -J- .:a:l'No: .;·; . ' ,, '' ·,l . . \ .'}, .. . , . ... ' '· ~ ' . , . , . -9- . :' ''., With this very simple thermodynamic'argument.one:can·see the reason ,: \.. ,., .~for lvhat.at first seems to .be quite a paradox: T.nat in these hit;h tempera- · ··. 't:ure vapors people are discovering compounds of' unusual oxidation states, -,,. .;•,'···-··· '/ .. '.' '' compounds of' very great complexity and what is even more ¢pnfusing, a tre- ~ .... ,.. · ~endous variety of''· compounds in a gi ve,n vapor. . ' This generalization has very 'great· practical importance because before -~ ; ' : . ' ' . ~· : .. . ' -.:.: · < ::this ~ras 'realized many people tried to extrapolate fr'om low temperature· . ' • , : ' ~ ~ ! • ...... ~, t~ I ~ • ' f > '> '' ·, ' ' ' --i . '. . ' : ' chemical b~havior directly to the ei:pectedbehavior at, hig}l temperatures ·.· i ..• ·t '· · ·. taking irito a~co~t' only those. species whichwere known. to be important ·at '. ,. . '· · · low tempe'ratures . '· t .,__ . •.1 . i .... One very striking example is the beryllia-steam reaction. It vras lmovn - ~ ·that at low-temperatures the beryllia was quite stable: in bontact ~-rith steam ·,1 .. ,and therefore it was not expected that anything should,happen at. high . ;' ,. . ' . . . . ' .. '. : : .: ' ·~ .. 15 16 .17 •temperatures, However when beryllia is ta...1<:en 'to hJ..gh tempera'tures ·!. ,.,..J ·in .. ·the presence of steam· it. vaporizes at a very rapid rate· to •form a complex ': . i. . ~ . . gaseous hydroxide. And this experience has occurred time and time again in . ','. high temperature systems. Sys~ems which show very simple behavior at lov . . ~- ' '· · · .. t~mperatures. with no indication of anything abnormal become very: complex and :; ';·' all types of unusual species come int6play at the higher temperatures and completely disrupt the. expected behavior. ; ~; . So it becomes quite clear that if ~re are to anticipate the sort of ~roblems ; ,, that ~rill. arise in· high temperature chemistry, vre must: :not base our experience ·.j 1· ..' orl.ly upon .the types of: molecules that ·we ;f:i.nd .. at low .t.emperatures. ·To the .• . -~ . ·.; first-approximation; we:must consider a1Fpossib1e- combinations of the elements. '' \ . . '• ' ' '. ''( "' ·: 'J:'hen throug:q. use of' the entrC?PY principles to::sori 9ut;. those vhich 'trill· have :• .; ' t i ~ ! . ·;, ' ' ; ·. ·: . : : 'i :. a:-:favorable :entro}?y of'::reaction, we· can restrict· ou!'selyes. to the several; 'q ,) ; }' ,, •• :: J ; • ~ : • - • • • • •• ~ • • • L·. ~ '.i ,··,, s'core species that coul.d be'' of' impo~tS:nce, eliminating>the many mUltitude:~ .. . ' -~ j •. ;• :·-t \; ·',. '', . ·, . . -~ . ·., ·s .? -~10- . ,. ·~ ., ;,_) •' ·' - '· ···, ! ~ ~ : .. ·-, .., ; .. ., '' 'f '\ I ). . •{ . '' ·. ' ~ : ~-· .: . i of species which .are not promising beqause of e.n U."lfavorable entropy of . . '. . ' ..... _.:.. '· ., . · :reaction.·:- Then we can ·sort out_ irom a..'!long the several. scores of. species r., !': .\. { ··.·:, . ,.. .•' ··'the ones which will be 'of the greatest import~ce by taking into account- .~- ., I. '· \ . - ' ' ' 'not only entropy changes but also· the' enthalpy changes. .. ; .··· ... _, ' . •:{ .. . ~. -~ : . ; J: It is quite clear,· them,. that. if ·we are' to sort. out the pos_sible species_ .' ~ ,l. -l .. ,.. : ,\· . '>t-,, ,$ ··, •·' that might be of importance we must be: able to estimate :entropy.' In low ...... ~ . . . ' . ,. l 'r' .; '· 1 ' 'tempe~ature'· chemistry -'the emphasis' is always placed on: estimating bond - . ' ' i ·.i· ::'I 'l- energies. It is quite _clear that at high temperatures:the emphasis must ··; be: put equally, if not more so~ on:t'he: ability to. e~timate entropies. I i-toUld like to go into a little detail on this problem of estimating entropies . . . .. -~-_j__ __ ~:-~_:_ ____ 9f high temperature species. __ . _ _ ...... ,.._ -...... ~.~·"-'":'' ~ ~"··---~---~·~- ______..... ~ ... ·~·--~--- ...... ·...... ~ . I '. <1\: --~ ·-·:·· Now, there are a n~~r of problems that must. be faced if we are to· :· . : . ' .. : _·._estimate the entropies of molecules. In the first place, we must kliow ·, L f ' • , something about. the structure. It obv:iously makes a difference whether a ' ' 18 Or if we have a molecule r · ' l:ke Mo o , .it is .going to make a difference \vhether it has a very compact 5 15 .,,.•' ':. structure or whether it stretched-out linear ' has~ st~cture~ So_one of ... -~ ~: . ;J< i_ the crucial· problems of high temperature chemistry at _the moment: is to gain ' : i .: t ·. . ~ '. .... ' :- --' S()me information_ about the 'structure- of these unusual ~nd complex molecules .. ·.;: ', i ,I •, .·: i \ ''. -1.. . : . ... · -'~ ·...... ;.. ·~-.~,. .... _;___:_~._--_.. ::.._~--· ·-! '-·~:~-~~~: ... ~~~~;-·-:--·;-~.=-·-;·~\; -··-·· ·• · .. ,.,.,,.,.,,"\';,~ ..-,. ·-·•' -~--· ~ •I ~...... , •. .;. • · •·- p•~.-. ,,...,..,.., ---···t·r·-..---~.-.<•• .;.. •. ,_. ....::.__. __ ..,._. -. .. ~.,,_, .... __. - ' . . ,Unfortunately,_. at; the moment, ·;we have very few tooi~ available. Hov : i . ~ . ,( i~ the 1varld wotUdyo~ _deteril).ine the .struct:ur~ ofMo o ? -:-. . this type 0;: In fact·,_ 8.s you will see. 'shortly, it is,~ extremely dii'ficul t · \" , .. ' ' • • /~.I , , , ' . ., , . . : . ~- :problem to unravel the :spectra even ol th~ diatomic, m~{~cules. :_ ': '.> '' ! ' ·' ' ''- :~ ! . :. ;~ t ·-:-, ._, '; ·. :. •,,·· . ; ) ·~ ::'.: . t ~ l ' . ' -11~ . r: - ...: ; \· : ·,.. .,{·"· ; \.' ' . ~ 'tl! \ -~/ ; 1 . "' ':. : ;:; :;.)' i .At .high temp~rature9 :the~{ is cpi:rsiderable excitciiion of rotation, of . · \ ... '. ~ ·~ .. \ .i :. i '1 ',' j . ~ ' -·yr.:~ ~ . '; . 'i .• ; vibration'~ and' of: electronic states and iil a molecule :'~f many atoms the spec-.·~' ·_:. '.1 ·; ::: ••'i· '\ ; .. •' .. ·, _,,: , ~rl.lm becomei so complex that optical spectra are very ;:difficult to use at ;,".· ," !: ~ ' ' . . ~ . .''4 . '. the present. · The' tools which are just· barely beginning to :be·. applied are · . ' .{_' ~ •. ~ '·'· ··r ~· ·molecular be'am techniques, where 'one ~an at least determine;{ ••hether the ' ~. ·:i . • . . . . . ·. ·, • ~~ l . : .has a· dipole moment. Some the work v;{lliam Klemperer,\(9/ ' ofl • ' . . . m~lecule tha~ ! ... ~ .. . ' . . '· . '. ;.-' f'or example/ has been 'doing ~'with the electric resonance molecular beam : -~ . ; method will be. very .. usef\il.:and will.~t·: least· establish 'whether these molecules ': ' , . . ' : - • . : . ' . . • . . I . . . • •. . ·~ ' .. .; ~ '~~ve ·dipole ·mom~nt~ oF not. . If a molecule doe~; not haje a 'dipole moment, . ' .. f ·' . . . . then that fCJ.Ct wil:L place severe ·;estricti~ns· on· the type of structure; <) ' ~ . ·)·. Electron difftaction techniques ~rhich could give additional' detail are applied . .. '. ~ . . ·.t'6' hi~h temperature' melecule~p·r··only with great difficcdty. . •· . . l . . . . - . Actually. one; of the great problems at the moment in trying to evaluate. ·.- .. ..• '.' the structures· ci:f the more complex molecules is. that;we have .no effective ,( . . i . . . tools ~t ha.i:ld .for this 'problem and this will be one of ,the severe problerns -: J that Will. have· to .. be tackled in the near future if ;.,re :are really to hav.e any ·substantial: U.nO,erstanding~.of the high temperature chemistry of these systems . . ;. ·.,; Now, ·:in additi.cm .to trying to est.ablish the structures of these high . .',':··- . : ·, temperaturemolecules, it is . .~· ._-; ; .··. levels of, the molecUles because at ..high temperatures th~ molecul~ is. not ' ., ~ re stri.cted to · just'·· a few low ·lying :levels' There i~ s~bst~tial excitation . . { ,i.. : ,:';. ',' : ; '.of vibration arid rotation~ .And p~ticularly since many of,the high temperature . I .:; ' : f·.! . i.; I '·· '! ,.. ·I· ' . . .• . -~ .. molecules are what one:would term radicals in that not all t~elelettrons~ar~:·,-· .. I. . . :; (i. . . . ' . '·. . . ' '' · :paired, there ~re often qUite low ~lectronic levels w~i~h are qu~te exten- ...... ,: 1 ' ; . :! : ;~ ~. . . •' l.. :' . : •:1 ~ ·: • ! : •: ~ively populated._·,': : ·, "' · ...• : , 1 ' . ·. . ~ I • ; ! ., 'l': · 1ilhat ~ I would: like to· do is to.' examirie .this propi~Ih for one ()f the :)impler . \: "" ~ :- . .. (. '·, cases, namely the. diatomic molecule, .because·we can say a little more about ,: . \ ., ' /' '; -12-·. _ .. , ... ; . ' . f ' ~ ' . : ~ . ' . ·' -~ ~ J·.:, ; --~ . :. _; ; :, the diatomi.C:: mofecule;. and. illustrate hovr i·le ·are attempting to f'ix the· ~ _- ' { ~. ' : -~- ·'!. ~ .;· ,e;ntropy arid a.·lso· the t;$ntPalpY- ot- .. ~fO~tion. of sOme o·r· the ·diatomic moleculeS. . .:· '· Nmr; for in fact, I think I i-TOuld say for most\- of .the diatomic . many ;.. ~.' ... _ t .- ·.. , ._·' high temperature molecules, we not only don't know the distribution of lovr ., '• ::,lying elec:tronic .levels, -vre don't even knm.; what the ground states of the ·"' m6lecules are ... For many of the high temperatu:ce molecules,:, extensive spectre..:. ' ~. . . :scopic. data ·.have been obtain~d by observation of emiss:i.cnfrom' electrically !'. ; :excited discharges.. In such discharges highly excited! electronic levels ·' . ~ are populated.and there is no assUrance that the spectra actually seen . r ·, . correspond to the ground .electronic state w·hich normally contributes most .< , .: , . r ~ ~ --- ! ! tO the fixing~ of th~ ,therni.odynal!lic properties· of these: molecules. · Obviously ·. '· .. i, .. that is going .. to have a pronounced effect upon the 'en~ropy we calcUlate ' . '. ,) ' '; ., ' .~ ' 'I :·1' for exanrole'. .. ~- - '· . ! ,.,., :·: ;· ., !. ., ,; ."j ·Hell, .not-r, hoi·l 'will vre go about fixing the ground' state? . One of the ' •, ~ I '·i :: '. .. ' :ni~thods whicl:l has been applied is to detennine which states' are seen in the. ' f : ~ f ; .. ,' . .., ~bsorption spectr~· of these.high temperature mc)lecules~ Un,fort~ately this.· . ,. 1 ! :·.~annat n~~lly give an unambiguous a:~'s1·rer ~ In high temper~tu:r'e vapors t,}:1~cre . ~ . "· :: ' ' ·, \ . . ~ . ' . . ; · ..:·,: ,.· .:r '. : ~ . :::-~.~;ill be substantial co~centratio~s~:not only in the groti.rid state but in a .,.. __ '· .l·· .. ··'i - ··.·r 1··· humber of .the io1·1. lying electronic levels. And the pa:r;ticular absorption · ... - .. ,. ~·:l ._·.;_ .. . :spectra that one sees ·just depends upon .accidents of the distributiOll ~ ', ' of'. .,. • ' , • ' ,l ~. ' • • .:; ; ·.' . these levels Sfld the ·particular spe,ctra ranges which happen to be convenient. ' "' •".: '· ;.• .· : .. A for describingthis is the examule: ;or the rilOlecule...... ·.. goocte~pi~ c2 ·. i .., . . The SvTan bands Of C lvere .well knmm tbat 2 des~ri~e~:~e-f'ore 'it:~~~S th~ , i. !· . ... ' • ··· ·.. : · .· ·' '2 I . . . ., .. :i · ·' . bands were due to'•diatol!lic. molecules .. : They 'i·;ere first :seeb\~· in 1802 and ·. '· ~-- .. '. :have been ,seen in' comets, star~,. fla..mes, electrical discharges. and other hic;h ,.... . •. •. • ' . • . _I ' " ' I ' ' ~ :;. .' ~ . l f ' . t~mperature: systems.; .In i927, one' hundred and tHenty-:five years. after tb.<2ir. ,· ,.· .·, :.- ',,,: -13-. .i• . . ,·; .:., ; ,· . ' ::f . . ' ·; i ::first observance, \here still "tvas violent controvers:(as to whether these bands -t' I : '·lere·due-to carbon alone or to oxides or. hydrogen .co~ou."lds of carbon. i·'· ';,i . . '.. , I - '! ,', . During 1927, the ~carrier _'t·las narroo..Jed. dmm to H , or and final~y c2 2 c2, c; ... _;) • • ~ • • : • "> _definitely to a. triplet state of c the vlork of JevJcins, 2 b~ ~uilik~n';E..ly' ~-·· '·'I 6 . , :·Barton, and 2 These Swan bands can ' ~~ '• . 1 ~nd Mulli~t~n:~She~~- ~· Meek~??: Prett~ ~·; ·.I ,, be seen in absorption ·in many systems; and it was ·commonly believed that the , · ?m-;er 371" state' of. :was the ground state. It has. recently been unambiguously . ., -~. c2 ..... ::establishe~ b~ ·B~U.i~frl~ ·Ra.msai~?/th~.~ the ground state o:f•c is not th~ , 2 . ~ . . . ' :'triplet but is a singlet state .' It just ~o happens that the available :.··. ···spectral regions where absorption spectra involving the singlet eround state ~:·. /. -can be seen. are -rather il=lacces·sible. ·.. They_ a:Ce either .,far .'off. into the infrared .'), '~ ... ,. ' . or far off, in the ultraviolet; so that it \:;as just a matter of accident ...... _·;: ! ::·that the triplet state lia.p:pened to be, so prominent iri abs~rption spectra ' ' . ' ' 'tlven though not the gro:un,d state. ' i·; . . : ".i ,·,·, Ari:long the. techni_q,ues that are being used in trying to establish the ',,( '', ,·.1- . . ~ ,·.· :For example, . one . '' : ; ; . . . . .: .i 1 I< ihe excited electronic states have a chance to decay out. :' Particularly . ·~ ..... '' ' :(;with some of the h~a~er molecules where spin prohibition 'is not so important·, .. :!.' . ' ·. -~·. ;: ; j . . . . l; , . ',: ':>.one might e':.::pect that after a reasonable 'dist.:ince inbsi. of :the molecules' :~·JH . . ~:~...... ·.., .. · r . 1 •·• 'would ·be in the ground ~tate~ 1'hen the abzor1)tion sp~ctrum of this molecular ·~·· , • .' ·~ , , , ~ •. • ' ~ ' \ ' ' . ·' ; , . I I , ...·.· 'i , •. ~·eam v1ouldi giye in~orinaticm. ori the gr:ound state. ,. : ' · ' ' i - .·, . :~. ,. :u . ' ' : ,., ' ' •.1 :' ,.· !·. .. ~ ,. ': :. 'i"j' i,') ,. .l ::1,' •,f ... .· '14 • '':·'' ••1 . - -- ' ,.'' ' ·' . ; '.';!( '1. ~~ , :! , .. · ·He have recently done some experiments of this t~e at Berke ley. : ~ ~ ~: :. ' >'::>,have ge4era:ted high temper~tUl~e; s:peci~s and, since we: could not! study them } . . . ' . i ·~· . ' -~ 'to e.scape 'into a vacuum as· a Ill.Olecru.a:r beam. · T'.aen ~re ·studied the o.bso:::-ption ·· • ., '·~ ~i I '•. '' :spectra of this· molecula:t- _beam at a distance at which .we ·tp.ought all the I ,.I ';' . ''. ~ . .•, ·' :.,,,, excited states. had decayed out • . . . ' . Obviously the molecular beamhas a loi.f optical density so we have . ' . ·._. '; . ~ ,' had to use multiple reflections across the beam, until finally we have had enoutih 'opticai' density to see the spectra. From com:parison .with ~ •! , I ''! \ .'- :' .spectra determined indischargesand high temperature. systems we have peen able to determine which states have ·persisted and have persisted .... . ~ ·and hive obtained informatio~ about· the ground states~: A detailed study of emission and absorption spectra zrom many sources .: \ should resolve the positions of lovr-lying electronic states. The problem, ; .: .'; 'i normally/ is that \·Te have ·too many spectra. For many of these high tCJ:;l}?Crature ~ ' ;·,. j .! . . _::!'.olecules many spectra are knmm and Ill.Ost 9f them have not,been analyzed. ~ ·, ' .. ·j . ; :Tlley have. been mu'ch too corn:J?lex to analyze. And there are .a number of . '·! ;; ,.. ' ' . '/. .·... / .. ::. i ;· ·•· ~~ .~ ' . ··; lying levels of hightemper~ture moledules. To illustrate one of the. ·scr.li- :·.·::: ' ·" . . . . ;· ...... ·.•.... ,;· : ~' -.; :·:: em'pirical'm~thods iV'hich hS.s proved very valuable, I vrould iike v~ry bric:'ly '\ -~. '• 'j. .. ' '; : : i _::·· ~! ~ . ·; _.' ~ ! ·; ,:t?: reView the: application o:f' molecular 'orbital corrleation~: .to the' prediction ',; :· .-!; -... j.! ':.j 3 ·,. ··· of. the lm-rlyingelectronic states o:fhicih tempe:r~t'ure~molecules. !·i~lil:cn\3.~, }-/·. '•:. ''/ . ;., ;. ,)' .. · :. . ) ~15-· -vras very successful many years ago in showing that the' electronic states of . ' . ' '-~ diatomic molecules could be rather well correlated in :term:s of molecular '•;::, The accumulation o:f much additional use some of the more recent data to see hovi far one can extrapolate these .. r. .: ~- correlations throughout the i·Thole periodic table. .· t ; . ·' ·: ~ You are all fa..."'liliar '1-ri-"ch the current theory of atomic .spec'troscop;~~./ The energy'of.ai:l electron added to nucleus depends upon the avails.- .;,, S:n~atoim.c bility of' atomic orbitals for each main s'l1ell corresponding to zero .::i....-·1cli.l.:lr momentu.'11, the s o'rbitals, one unit of an.gular momentum, the p orbitals, .tim . ) j Units Of angular :momentum., the d orbitals, etc. T'ne 9rder .in Hhich the . 1 -l.'· . i ' ' atomic orbitals are filled is rather uell established~:·! The molecular orbital theory assu,-ues that electrons s.dded to ::-:. group '}.' .. I·.. . : ··.of .nuclei will also add in a definite. order depending: upon the avaiLJ.bility . ' . o'f molecular orbitals. : ;; : , . ·Only the vale:r.1.ce electrons, .that is thos~ electrons .' ~ • beyond a closed shell,'. are considered. The electrons in closed atomj_c · '/ . /. -1 -.. . ' shells are assur.J.ed. to be restricted to a single nucleus ·,;hereas the valence electrons are consider.ed to be spread :out around all the nuclei. ~;e proce~ding 'by the molecular. orb~tal approach, . we don •t ·care 'lui te so . ... . ' '.l -:_ '.' .. "' ·' much \·7b.at the nuclei are~ 'I'he idea is that ·He are just tossing these ' ·( . . ,' ' '. . ~ ' . :· - ...... , :; :electrons; OfltO the group of nuclei an~ the order in Hhich they 1-l'ill fill,. )'l;_;.; _. . : ..- . ·. .•.\' · · in is not extremely :dependent ~pon the particu.J..ar. nuclei. \'l'he order of: ~ > ' I_· • , • • ' • : ' ' • ' • .. ' ':' • ( '· ·.filling is indicated in Fig. 5 ·for rrJ.Cilecule.s vrhich r...avc nine electron:; out-"' : ,, ~ ' .. side the closed sh:ll_,-..· · su~h as N;, a."lcl other ~..olecU:les !are :Oho·.-rn \·Thich \J.ll . ' . ;:: :."t-rould be cl<3,ssified as. nine-electron molecules. Just :as fqr ato!:rlic or;oit.:lls, ' tl:ie molecular· onbitals .i·rill oe .classified· in terms of' anuul.ar rr..oment.:::.. I." or molecular orbitals of a diatomic molecule .the angular ·mo~enta. of the c.lcct:·o:"l::; '·; ,·; . -l5a- .. ,·'" 'j -i·.'l. -;...... -. = •. ; \ : l :_ t: .•, t ·• ~~ ~ ,·.· .; l ~ i Molccula:r o:t~bitels fc:r 9-elect~o~i 'liiol.;1ctU.es'. } .: : .-·· .. . 0 ;, ·.. -2 2 b~ 2·'- ,; :· ,z.cr ycrx.cr WIT - ·· :B Z · · r = l.d3A ,, •l,. ,, •>, ':I 2 ,' 2 2 2.;._ ·-! ~. 3 . zcr ycr .xcr i·n, A H r = l.i8 ··. ' ~ "'\ \"" : ,-· ;. --.:; 1. .l~ -1.12 .t ·. ·-. -!) ;~ ' E::C:J:t.9le_3: C? ~ BO, ::BS, AlO · 1. . :-· .· r -~ .' ·-1' • i '· tl :-, !· .~ .;. .' ;-, .... I ;1: .. ' ~' t·' .: .-.,.- .f .;•• ·,, ·.I ·. i ~-- ··L ; '· -~J . i.·.- ',' '"·.;- .;-' ~-- f '' i -~ ; .. ? ~- ::. '··· " :.,__ .... · ).' ·)' .... \ .... •. . I .. ~: ; ·_,. ),·' ' ·. ·'; .. . ' ... ;.1 ·,t ., ·• r ·in an orbitalare taken with r~spect to the inte.rnuclear a.Xis. For o, 1,· ..l ,: 'and 2 units of ~guia:s momenta, the molecu~r orbitalstare::called ·sigma> {cr), ) • ..: . . £ ~ . ·.. 1. . , .P~ (1T), and de.lta. (o) orbitals •res:pebtively, by analo~. to·· the s,. P; and~ ·r -... .'' ;I •. . 1 d 'atomic orbitals. For molecules of light atoms, the:molecular orbitals are t ,; also classified as bonding or anti;;.bonding depending upon w·hether the ;, ·1 {>. r: -~ . add.ition:·of.::an .electron to an orbital causes a contraction or expansion of t.· the internuclea~ distance. t· ':.· . Hullike~:v"h~s 'suggested that' each o:i:.'bital be labbled 1-lith a letter . ' . 7 :to indicate the usual order of energy or order of filling. 1 The order is, '\' 2 2 . 2. . 4 . ·4 . 2 . . . . .zcr , ycr , xcr , mr , vrr ·, -ucr where the z orbital is filled first or has ·the lo-vrest energy, y is next, etc. The supe::cscripts on the cr or. 7r indicate the maximum number of electrons that can be filled in.•a.given orbital -vrhich ·' I~!,' ••• ~ ... ' • is two for sigma. orbitals and four: for pi or-bitals. . The xcr and 1m orbitals . ' ' . .._ .. • ' ·,. ' . . ·. '! ··•. . ' .. ';1 -. j . : ,:, : .'are very close in energy3~,}3 for the molecules of interest here and the '•TIT' · • orbital is often filled before· the oTbital: I i-TOn •t 'n:o ·.. into the Hay that xcr . . ' 0 . • \'! ·' ·. r these. are· ~orrelated. to the atomic states from Hhich these are derived,· I ...·' ', .think for OUr purposes -vre can look at 'this in a completely empirical manner · ·:; .+"'...·e obse:r""''ed 2 34 3 +' ·and i:fe can find .that -vre can correlate ...... , . . v . .stat·e·~s_ .·.',,.,.....'. .}····o· • the · 1 .molecule vrith.a building up of electrons in molecular orbitals. ·The dlectrons · in the sigma orbitals are concentrated along the internucle~r axis. The· I .· \ e;Lectrons in.pi orbitals will have cylind:i:-ical symmet:d- with respect to the ' ' ~ ;r ;•, ·· t \. ., .·· · internuclear a..-.::is ~·- _·. . ,. I : .. Nm:,~: if vie. fili in nine electrons ue find that four of them go into_ the . ' ~<: i• ; \I •' -i' . i · lOiole st ·sigma orbitals and: v1e find for a large. number of. these nine e le ctrori · ; . ' '·' . ' . ·, '• \.!: ·;._; molecules that the vrlr orbital is slightly loi.;er in energy t:b.an the XCJ' o::rbital ';; .1: . ; / . ~ . ' . 1 . · : , . I . ' . · ~ ·. · . ' ' . • • i r • ~. : • • • •• :' ~ . and it will: _nO~lly be.. filled ~p· firs.t before·. xcr orbital ... : The _confit;u.ro.t:Lon !'i ·.·'2 .. 2 ', 4.' :-,:'· .. ·. :_· .. _·: .'\' · .. ,,, Z(l' -ycr.:.oi:cr 1-nr col~responds to what one finds empiricallyias the· lovrest configura- . ;, 2 I· tion and it -gives only one possible electronic state:, .-the 1: state. In the ' ~' ,· . . f ~ . ' ~ ~; ~ -17- '' ::;,,( ·,, . .-. l· , : , case .of atomS~ for a· giyen electronic congiguratiorr there are various . ' ' ~ . ;·! .. ··• combinations' of spin and angular moment~ 'lvhich give different electronic . . :_ . , I 1_ -;:i . . states~ Like1vise, here 1ve will have various molecular states. Completely ~.: : .. ·L ~ ~: 1 . . ' . . ' . . ' ' 2 ! ... I;; :filled ·or:bitals·he:ve no spin .or momenta contributicm.s. The Z state has i l 't I, ;:J 'i l i:: no orbital angular momentum because all the orbita~s: ~re. compietely :filled . I .. , , • except :for one sigma o1~bi tal; it is a doublet state' beca;se there is only . . ~ . 1 ·) > • ·; ~ i I . !: /' '' , one unpaired 'electron. . ·' i . ' ' . I ... ,·;' I '·' The next highest elec~ron configuration corresp'onds, to exciting one : .] 1 : - '·. . "; ' l ,:) electron :from the iV'IT' orbital to the xa orbital and ,t.his, again, will yield I '1 l ·' 1a doublet state wit):l one lliJ.paired electron, but now ;there is one unit of l ., .;. -~-_;)· l ·-; 1 '! . >:.orbital angular:nmm~ntum and it 1.:i11 be a pi s·t;ate .. l : ·i' ' •[l -~' . . .;1 Th~ ·~nex"c. configuration corresponds .to tlOVing an electron u:p ·from the ,'•• . .'I j .. . 2 . ' . ' ya orbital and yields a Z molecular state. · Generally where the spe ct:m of'. ; ' l' j ·_; '· ! I :::! the nine: electron molecules are. complete tr..:Ls is alYr~ys f'ou.'ld to be the l ''' ~.- ,,' ·.. ' 2 ., 1 ' : . ·.. ~ order of the electronic states: The grou...11d state is Z;: the first excited j. . •.. -· ,. 2 2 ·. '· ,_ state is rr a.Ild the second excited ·.state is L:. Nm·~, 1-re can assign to . ~,.: . : . ' 0 '~•• ···these orbitals a character designated as anti-bonding or bonding and it ., : .· I ; i ,:. ~ ·. 'i- f . j' ...- \ '! .·. so happens, fOJ:'. exainple, that the ya orbital is antibonding and an electron ,. ·,. - -·~ . ·: ::: in an antibonding orbital tends ·to !msh the nuclei ·~part. The z, x and ,., :!·· . ' ·, \ ' - . . ~ ' . - ' ,,·· 2 ,I; • ;; ~ orbitals. are all bonding. You will. notice that the :excited z state co:::-rez.;. "; "::' ponds. to. moving an electron out .of .the' antibonding ;~a orbital to the bonding :-·· xo· orbitaL .The excited electronic state l·lhich has 'more energy is rr.ore · ' ··: ,. . ), ·t.· ·. ~ '··tightly bound as ·far as. internuclear distance· is concerned~ . -~ about the bonding a.n:d antibonding character of' these orbitals; is ofte:n very ·· :r1~1- '' r.:•.;: ~ ...... ~: ~;: useful in allOiving .us to correlate. ;the observed levels 'tvi th the electron ! '~ :' J~ j "t' • ~: ' .. l \ ~ orbi tai configUrations: ~-f ! <:. From correlations of this type one :finds in 1nany instances tl.<.at one·· 'i .· can characterize the spectra in terms of molecular orbitals; and the. strikinG ·; :! .: ! . ' -18- t ! '•. ~· ' .. ;. .. :thing is that the variation of the 'excitation energy of' these .ievels . }. '; ..; ' c1oes not vary greatly, for the most part, over a la.r(!re part of the • f . periodic . table. This .is illustrated.. in Fig. 6. . ' ' ~ ,,,,: Here :-vre · ha·ie data for some·. nine· electron molecules and you >·Till notice .·: '·.:;~:r.at for; the A. state i;he excitation energy varies only sloHly as vle move •· · ·along to heavier and heavier molecules. In going :from calcium fluoride . ) .I· : ~ . . i '.~ . . . . ' •'i f_, ., 'to barium chloride there .is a SUrpri.sing.iy SID.:l.ll Variation in these ·.(...... ~ ... ; exci tat,ion energies which are given in thousands of wave numbers.' Hherc i 1 .. ·• ' . ··,: · :data are missing for either the A, orB levels, >·Te ·could rr..ike a pretty good ' ~ . '·: ' ~ .:; ~- ,; { .. ·;.guess as to vThere to look for a transition involvingthe A orB states. •:•· ..r ·. ,· ·,. .·; .. I:f 'tve. consider the .1·Thole group of nine electron molecules ~!e find, in ·.: I! ·~ ·,i i• I_: I . ·.. :'fact, there are some substantia],: shifts, particUlarly; lvhe~ "i·Te 80 to. · ' · · compounds ~f the. fir~t roi-l of'elemen~s, 1itl1iu.."li to fl~oririe. ?or nine ; ... • i . 'electron compou..J.ds of that group,.· the A· state· is some\·rhat .:lo1·1er in encrSY, ' . ··: l ~- . (' < ' , .· ·.. ·the B state are soi.ne~:rhat higher and the levels come· closer toe;ether for. the '·!··.•. . '. . . ' . 1 ' . . .. · .. ' , •. ,.i heavier molecules • .:. 1'. .. ' . ·. . ·,/ :· '' ., ·.. Figure 7 shovrs the situation for 10 electron molecules:. And here .·, •! .. :.;. .. •!" ·:; ,,.\ ·., i·le don 1 t ·care vThether ive are dealing yith nitrogen, phosphor-u.s or com.bim.tions. , . . . ·of fifth group elements or fourth group elemen:ts Hi th, sixth group elements, i•' .~ :or third' group elements lvith the halides. They are all 10 electron molecules. . . i . '" , \;rney shoul,d behaye.:similarly as far: as ·their excitJj:; : j electroni~ stc.tes a:rq ( :: .;,: ' '·. . ( ·~!concerned.·· .. . , 'n -.{>I: ·'.'. · . Nmv-, we .have enough electrons to fill all of the~ first four orbit8.ls. ·.. . ' ·:· ',!.:' · The next higher o::cbitals are antibonding orbitals and it no1~lly reCJ.uires :! .. substantial excitation to move an elec'cron to tho$e orbitals • .. . ''; ..1 • '' l ;:·:.· t .~·~· ... ' .·~ vhere all the orbitals ·w·ere filled, there are. no· unpaired electrons and no ;·: . ~ , ;orbital a.YJ.gular momentum; we can only haY predict that ·all of these molecules tiill have a singlet sigw.a ground stute ~ Tnis is found to be so. . "P. . : ·.:. -.Lua-: ., •' . ~ ; '!-· • . ·'· !.: ; .t· ' ., . 'I ··. ~ ·:, :! _. ___. __ .:.;,...... _ ___ _ .. .•' Co.F ·cut1· ' ... ' CoEr 16~9' 16.1;. '' . ~ 15.3 '': ·.... ·: ·.. . ' ·~. ·: EaCl ~ .. 15)·!-· J)~ .. 0 . ' .. ~ ~ ~) ··o· .. .A1T .l.L.. 11.0 I I ., I ·' ._, '·, . ' - . . ---·-- ------~------:'I ~ i !. -! • ' ~ \ I -:·· .. , : .I .·:. ~ . . l )· ' ·< ,. ' ,. ' 'i,, ? '. .., ;; r , '··' .· ; r . '. ;. ~ '~. ., ··,'t ( t· •,·,, .·. \• . -~ .· . .. ,, ,· -·:.· ,.· \~ ' ·.t ·. ·.! .r:· . ~ ' ~··. .l. • j • ·~ '. ~ , • ·,I . ,.:. . -~-·· ,. ,, .·. -·._1') ···.: _,·,.. .:;. t...... '.•.1. .,•, ·''. ' ., ~--. l~ '·• i ·:- ··J . ~''' ! . I 1 ~ . ;, . . ' -~ ' {. ·~' r '· ':,,' ·l --.:...._._---=--.·---·.. _...... ~.;.-·---···"_:... ______------' . ----·--·--~-~· -'--'--'-·-'-"---·.;. __ ;. ~ l. ''· .. 2 . ···' zo~)~ xrl~r?~r/ '' .. , . -; , .. ' ' ~- ' " 2 ycr 2 4'"'.11rr 4 za ... · ;w. .._...... '' I I . ~. ~ ; ··1 ".! '· r .. -~ ·.. i ;. •I ~', _:;I ; r .. .- {· \: :) '.i ·I' •'• . > .,; . I • l' ·' !' '• ·' :., •. ! ··;.'' :;. ... j .<· ; I :1-, . -~· : ''• ;< ·': \ ;l 1:, I i',· I. '.' ~ .' ..: .·: ~ ·~ ...... ; i: ..:r• . .: .. t:: ··::' . ' r_.' '-~' ,I ··,i. ,:r ,.'·•i l f .. · .. ~- ~... ' r ~' ' -~- It . .,.•· :·. . -~ :'. .. ~·! p '· ~. ; i ·_',i·- -i ' ' ···. ' ; '' , I , I, ..;19- 'I • Inc:i.dentally;·1.rhen I say halides· in all of mY present· disc~ssion, .·· .- '• '· ';,. , ·I: am talking about diatomi.c molecules; so these are thc halides ~of boron I < Cl.luminum and gallium. in the one oxidation state. It is found e}..verim.cntally . ~ . -! ,· ·r ·~that all of these molecules do have the singlet sigma ground state. The '··- ' ? ~. next highest excited states generally the singletpi and t)J.e triplet , I \ ~ :: .. \ '•' I • . -: } ·• 1 ·~ · ~pi, -.the triplet pi befug ~loWer ---i~_ eilergtJ than the si~giet pi. Nm.; :for the . ' . - ,; first time,· we have an molecular orbital configuration for which there are ''; :! • '•, .. '' tvro electronic states. There is one electron in the sigma orbital and one ·.in the :pi. , There ~Till be one unit of': orbital angular 'momentum, so I-TC 1vill '(i i . ~ ·l · 6nly get pi state; but the t1-ro unpaired electrons can either combine to '·.pair their spins, or to reinforce one· a.'llother ·1-rhich gives .a singlet and a 'i·,, ·, triplet'' state ivhich do not have identical energies. Generally in a situation ; ,: : ·like this, the triplet state is lo1-rer in enert,ry than 'the singlet state. ~.' . ' . .... ·_ . 6 J••: ' . . . ( ~cco~ding to Hund.'s rule~0~./J., ,. .. for the splitting of enerGY: leveis of a .common configura,:tion ..' The wTf orbital is slightly lo1.;rer in energy than· the . ' ' . xcr orbital so that if.. any orbital' r..as to give up an c~ectron ·from the ,; •' ' i ' ... ,ground state configuration it lvill be the XO' orbital; :and the only possibility .': ; ' '1. 'is to go to the. next higher antibonding orbital. Thus the Tf and 3ii' states ' ' .bE.ve considerably larger internuclear distances' than -Ghe ground; stc.te. ; ' ~ '4:),, Then -v:e have· various combination's atiJ.ong these orl:ii tals ·just as HC ·had · ·' i '. ;· . . v ' ;, '! ';. ' ,for the nir:e electron molecules. ·But for, 'pur :pu....'l;>ose 'I i·Tould like to I ; g·' ·, I . • ~ - ·concentrate on the thl"ee states due to the ~iil·io. configurations of lmrcst ·, i ·; ·:.. :·; ·, ,( ' ' ',energy. I vlOuld like to make some gEme:calizations' from the data. l·le haye ., . . . ' ' •·" r.::: >available for these states and then t'J:'/ to extrapolate to :'molec';lles :tor 'i'!hich. •• l ''· . . • ''' • ·: '!, .:we have no· data and to illustrate a .l-ittle !l".ore. ~learly the sort of :oroblcm .· · ~ . . '.{ i : .. . . ·.. ' . . .; ~. '. ;,· ~ ~ ~ · ' •that we have 1vith h:i.gh temperature moleculc::s. . I ' ' . ~ : : l>ly :problem is this: · I am interested in compounds of all the elernC:nts of the periodic 'table. I -vrould like to predict the ground states <.lJJ,d the .: ; . ·' ....' ·. ·' . ' .J ' ~. '.; ;.· :; ' -20- .. ~ ''.. ·t' . ·' :9,ositions or 'excited electronic states :for all the molecules of :the ]?eriodic \' ·; ·table. To do th.it; I have to be able ·to predict hO'i.;r the energies OJ.~ the \ . 1:· . . . ·•. ' . . .•: ! ' } ·' ·. '::iolecula.r; orbital configurations vary across the periodic table,. toot is, ., . 1, -t '; . . ~ 1 ' 'I t.he a.vel~a.ge ener[f;Y or each con:figuration, · and.. ho1-1 the· splitting 'varies ' J ... ', i:i-nere there are several states coming fro:r:l the same configUration. 'I a..'il :._ i going to examine· t!l.e availa."ole data for the "Yrhole periodic; table. Let us .. look at the available data.. in Fig. 8. . l. ._i. ·First :1. I· a1-:1 going to examine the .energy dif.ference o:r;· ·splitting "oetueeri 1 ... t:!'le ,3rr and rr·states arising from the same configuration. l-le do kno\·1 the . splitting for the molecules I have· indicated here 7 ·and we Will find tha.t as ' . . . ' we go from the very light. molecules to the heavy molecules the splittine; C:ecreases; 'but as 'He -vrill see in a oon:cnt i·Then i·le compare -vrith some otb.tir . "(. . -1 · nu;nbers :t · this change is. a very. sir:.all one .. Tne IDD.ximum cr..ange i'rom 10, 000 · em · 1 ·· ... , ' to 6, 000 .em-:- :is a relatively s;:;:;all change. i·. ' :.: ' say the splitting changes hardly at a+J. over a large J:)art of the periodic . I .. :•• I ..' '. J 'I ·!. ::,: Noi·l ,::this. ivill be of sor::.e importance because I wi:ll >·m.nt tq make a r.1.ther j ;: . l ".' far extrapolation in assumi:r...g tJ:l.at -v1e: can take the irifonr,.:.:tio:n. we have from ..' . one pa:rt of the perioidc table on how·· much the splitting will be and usc the ·..• i ., . . ' same values· elsewhere in the periodic. table: In Fig." ,9 we · are comparing 'the . . ' . . :· • .. : ·.; 't . ,\ .., , relative energies··of.the two singlet levels coming from the first two . ' .; . I ; I. ·' • ' •• configurations Of·. the 10 electron molecules. A group of 10 ~lectron ~ • 'I •·' ; 1 • I •,, molecules is shown.' ..You see they needn't be neutral; CF+ is a very nice 1 · · .10 electron molecule. All of theseO:have a 1: ground state and here I have ' . . 1 'Ill - '·'. 'i 'given the. energy. ot the 1T. state of the first excited configuration ~la.tive 1' . . ' ' : '· .: ~o the ground smte •..·You will note a· rapid decrease in the excitation of '' .:the first electron co:b.figuratio; .reul.tive to the ground one as one goes to the heavier molecules, starting with the order of 70,000 wavenum.bers. You f, I. ·,. I:,·' ' t. 1- >,' .:.2do:- ,. ' ... . >-· ':' }, _L'igurc.- 8. : 1 ..... '"ll- "" 1' 0-.) \ ·. (.'··• : ~"- . I • ~------~-·~------~------~----~---· ---·~--~------~---~------~ t, ...... ,•" ,. ·...... • J .,.,i co ·, '.: ·.\ i. ; '· [;\ -~ i f 10 16 ., '· i ll~ 12.:f 9 ·' . :-· ~ i! .. ~ ' Gal§'··· G;;:.Cl: 'acEr : .J .f; 13 io::: 6 :-· t' 'I I I ; ! 12 ·." l :. i.' ' ~ ; .; . . _(;. ·. (. ·'' \': ,.' . i ~ . . '' •,j ·t I : .. -~ ,, . ' ·,: .. •.. · . • ...... .. \ ··, .. . :i ,. \. '· '' ':_ . . f ,·_,, · ...;· t .•. i· t:' : ~ . •: .:, ;'• '·!,jl ··.;r \. .;., ' { ~- -:..I 2' '·· '' :·, ~. ' ' ~ ,. ' 'j ;.: -2'0b- •I . ' r·!r . r.... ~· ' ' ... ·• '1 :C·:~~ lG. "'ci '\tl.f ( ' .:' ~ ' \ .. · of' . 't ~ : .,,I ,·, ' I ~ ·, ._ ~ ~! ' i .. . . ' -: : - .- . - - --·--~----~----~--~----~4 ., ' •'. j, .( .• ·.I ?: ~ l ·., ..,. i _.; ' '·' I i ; co SiC G-c:O. ' ! )~ ~J ' I "r_).' ·29.5 ,; ,! :SC1' ·• ~ ! 57 51 : ; ; : f. j .. ...,._.,....,.. ----·~----··--·,_ ' I ___ __,____ ------..,...------··~------· ... ---·;.-,;...-----.~-~---..:..-~---:--,;.....____- ' •, !- ~- I I I I ,I I • .., .. ' ;' ~ .... .,,, ; I I Y· .. ~; ' :E :t ~ . \ ' 'i.:. ,. ~ : ) '· :' .I.' {l ;: t \; r -, N. I , I .,_ < ·',· -rt ! 1.. ; .. •. ·( ~ ;.; ,• I .,· ,r _'II < f ' ·., ''· .. ':• .. \ ;~ 'i :.r, .. , ;_ i ; •. -~ r; l }'. ·.i ~t r ,. . ~' . I. ~--~ ·~ I :., r' :~ ·• .. ·;_: .. ' '"'f i' f ~: . ;.' ,;· -~ ,. _:, f 1j_ l '''· 'I ·_;l -\ .·-~... 'f '-21-' ~' , ;·:. will notice that we have oxides, nitrides,' and halides and they all shOw·. 'l the same order of excited states.' ·It is rather interesting to compare 'i ·'. mOlecules like.SiO and BCl which have th~:/ same number of to~l electrons~ •. :J . ·!• • .: ·.-. ' 1 .. ·,.I including inner shells; and you get close comparisons. · · · .' . ~ . ' ( ') ., ·.' . .: Figure: 10 shows an additional comparison going to even' heaner' oolccules. ., · · These. are. of 'the. same :type that we, had in Fig. 9 bu,t there .ivasn '~ roo~ for "S ' all of. them on the same slide . And we notice a steady decrease in cxciU:.tion . -~ ., ::. energy. ~le have dropped from 70.,000 wavenUr.-ibe::i:'::( to 28,000 -vravenumbc::::s, a ' -~ ' .. quite drastic drop. · ~le i·TOn 1t :have the time today.to go all throuch the . ~{ ·.. ~ data. Ii' one takes all the data that.a::::e 'available;th~y cri.n be correlated ' ' ' .to molecular. orbital. configurations~ and 1·18 find that s.s .He go to the heavier . .:; ' ,. · :molecules of the :Qericdic table the e:J.erw separations ~of the various ' molecular orbital' configurations stead'ily '· \ configuration does not vacy rapidly across the periodic table compared to '; < .. .• the separation of. the average energies of different. ~onfigurations. Figure . l •. t j '' ll shows the states for eight electron molecules such as c , BN, and the. .. t 2 j ' alkaline earths. ~- have left off the · zcr orbital, ·the .first sigma orb.ital, ,·; ' . . . . • because it is .unaffected~ -With only ~ight electrons w~ fill up the wrr 'i \ and won't .put any.into the xcr orbital.whiC?h you·remember had only one el~ctron. 1 in the case of the ground state of 'the: ni~e electron nidlecules. ;A l: state . ~ . ~ . . .~ . : . ' : r, 2 2 4 2 to zcr ycr wrr is to be -for c .and for . ',,' c,~;rrespondi~g f~und th~ .gro~d .~tate 9 2 ;, :I ~. ! ~other light ~ight~electron molecules. :; .. ,·. '! ;j . ·~ ..~ I '· .· :"'21.D.- ' -~ . '. ··' l ~· . r : ~ ) . . . > ..' \ ·I ~' ;, ·.?, . ' ·-;i.;·-" .. '. . ' ' ,·l ,, , .. .: ... ·."'· )'· ;.: ·.: . '•.· t ,;• i Ali . ·' ;.,r':· '• ::P·· .,.' 31. .·GttCl G !·; ...•:; : i': ·------~----~ ·------~~~------·------~------~------·------ . .'{· ·, -~ I '! ··. ' ..... ' ,:, . t L •,'. ' r.. •. , .. •' ...... ,. '. ·:' .. ~- .I· ... '~ . ·. ~ '·; -~' '·t •• ~ 1 ,. •.t 'I ;;: i . { ~ ' :~ .. -:.. ,, . .. ~ '" ~: 1 ) ·;, '· ..;. ~!... I ·-21b- 1·. . ,·: £' ·:,! ., i' :r. •·' ;: l, '•' . ; : :t.::olc- c:...tlC~.-~ ·· '· . ; .· 1." ~- .. ' ~· ... . ' . ' . . . ···---.--~--:------...... -----·---· .... ---. -·-----:·-·-----.--~-.. ..__-:.-.-~---.-~- ~..;..··------r--·------·------~-- ·----··--- .. ~ .. ·j ·.·. 4 1;~ - ..v-:r :>l'f; ., ' ' : ~'. .f ., .f I .. ·. : -~ d' .. 1 H · · [':; , 3 - · . "·t·\. ,··'. :.L .. ,..;.. ' ..,, , . -c:.- -;.:; J• -. ..<. ,. .· 3 -~ ~~rrr:·. .. "}~~ ; >' ··,,.,_ -,. ... ' : ~ .,· 1~,+· 1.· ·is '· :' : j -·-··------~.....-.-- ·--·~-·-.,...... -----"------.,...... ~-... ---~-....; . __ ------'-·------·~-·-·"--.--..-.-,.-- . '' (' '~ . 1:' '#. !• ,. r •·.'!,' ~ .~ ...... J . ~ ... •'; : ~ .. ;:; r· ',,. ·I·! ~~ 1'' ,. ' ·:~ f L· !r.tl I· ' 't '· . ' .. · . nj'•·' ~:; ': ~ I . " •' I· ·. l . ~ . _.,.. ... '·, '!- . ':: . ) '' 'j . l. .· ~ '~-· ' ~ . : .~ , I ~ •, -22- .~ >~ ;: ' ·. .. . .' . ~. ;' <: Now, wha.t'\about.~he•next configttration?. ·The ·next configurat-ion· l ·, ' -, ' ' ' ~:''' o \ : : : ~·' I' ' : • ' ; '' ' } ~ • ~ ' • • f 'o • ;, . t- -· ·.. .; ';:..: :i.:corresponds to mov:Ln{(an elebtroz(from the' I·~ orbitailto the xcr:orbital. l-1.: --~;. ,,;·:- ··:~ .. : .· ,. ,' .' ~ -.~-f\ ·-:;._ 1. ;':~;''ii.he xcr and the~~ orb:i.tlil$ a~r~'vecy' clo~~ together: i~·energy~ They are·. " : f . -.;··-·'' ... ·:··: -~ .. f' ;, l ;I . ~ . ·_ ·_ . ·. ' ;,'.. I ' • .:: • .. i ::. :J:;>oth bondin~forbitals. 'J;'he xcr qrbita:l, 'tor mbst' of themolecules ue are ' <:. . . ..- ~ ., '' ·. ·. .· ?J~onsidering, • is ·slightly •higher in en~:~.·gy, than the ·,.nt orbital,: but not . ·... . '( . . '. . ,. .,._. much. The· eigh:.c-:-electron molecules· have excited o'rbitals ;~r excited . . -~ ;+{ 'l ::configurations corresponding to' interc:b..anging electrons be,tvreen' bonding':. ' . \. \, ~~~? ~ ! . ' . i • . . ' i:. ; . '· · · .':orbitals, not moving electrons from' bonding orbi.icals .:~o a..r'l~ibonding, •·rhich '· '..: '' ' ; "' ' ' .. ' ' -~· i :, !' : ....+ :· . ;_: . ;requires big 'energy jumps.· 'The tem-electxon, ·molecul~~ ;rea.lly \.;ere not of ·, . , i. ;~oo ·much conce:i."ll to us from the'· h~gh ter.1l)erature :90i1it :of .\rie'iot b~causc tb.e .., "' . ' ': i . . ~ :, ~ ; :··· ·.· . . , ~ I ; excitation.. energies of the· first extited le\rels ·.were :so hieh, ·except for·· the· ., . . ~ .. ,'•/ .• !' ..• :.z~2yc/-mr4. and.• the zcr2ycr2xo- ~~ con_fi~~·atio~s is ~ .' ' f splitting of the 3JT' and \r states 6f the later configuration, the 3it state. ,;, .... · . i: 'I •. <; . 'rrey fallbelow. the . i: state. :nm.r, · that t s going to makb. a tremendous • ,.~ '' ·diffe:Cerice.in. calculating an entropy._; Depending'upon>::hether the groUl1d state '~Z or '3Tr 'there could be at least a· .factor of 6 error< in the partition .·~ '~ 't .·, : . ' :> ~ ·. . .~ : f~nction 0~ in' the concentration' tha:~: one .would cs.lculfi te from the he:: at o:f >· .. : i·', formation of the 'compolllld and the calculated entropy~' :The error of a factpr ; .. ';, of six due 'to" the ratio of degerie~acy of·-;i:;h~ct~ro states might be' : . ·. . (. '\, '•' ~. ' • < ,· '' .• ·( .i' ~· .: ' ... 1', -:-23.- ., 1 ,, to~ a :facto:::-.. o:f' ten i:t' one ta.~es into account the di:f:f~renc~s in inte:mu.clec.r '.l. ; i . 1 distances and the vibrational frequencieB. one \-ioUld be: in. (. l .error by an order' of ;magnitude if it is c.ssumcd, .as everybody does :foj.~ 8 }. . ~ ·.. ' .·· 3 electron molecules,· that the ground st::.te stai~.~ ~~ .; .I "t.;culd. like. ncm ·· to · convince you .that 8 elec~~ron hig."-1 3 teiiperature molecules. f'ol" 't·rhich J~he grotu1d state 'Hill be Tf • .: .. '· :_-:. l :from some of the rn.olecula.r orbitals v:hich are listed. in Fie. ll in the a?_proxirrJZ. te. ordcr<~of' the average energies of·· each configuration. ·-.:: . ;: iealize that each o:fthe set of: states : i :'i.fill be ·s::?li t ~ · And I have \·rritten the:m in the order of' inc:::-easi~Z cncr::;:r: ;.1 .-: ·' e.g. It is obvious ~na~ ''';:.. th.er~·· is of a.i:tfcrenx. co~J.f:i,c;m·a·~ions ;. t ,. ' ·~ ' r ' . ·the same number of' bonding electrons . ':::'h:: i'iJ;"s "..; s ta tc iccr:d:~ sr;oncling "..;o an ;; • ! '' OUter antibcnd.il'l(; Orbital is a \r vli t~ a Yll'..~cl{· l """1: -;. !-.. ,.. ~..;< ' · ...... :. ur·-._~ .--, 2 ....._.., ""'"''S·"'•·"-:-~'s__ --•v ,..,+h C·ClO.v8. ' -'- :r.or··sOl:l<::·u~ q. e. 1· ·"..: ct."ron·_ L"..O..LCCU.l·2S... ' - :: .. i -? fj>-;,.,. "~;;here le:;elS 0 .- ·. .··~o· 11 the .. correlltioh bet;·reen these are.listed.·in Fig. l2'in ' • • '; • •, • I ' _'. ~ ' :o .._. :'·' i. l'·' ~'t·li:th the. correlation beti·ieen states and :mol·::!CUlar Ol'bital I· ·;· .,, <, :· !" ·. i ' J:~clicatcd: It 1-Till· be ·noticed that the ·energy of each [ co~i'ic;;,.crn. tion. is , ~ 1. de:creasing as -i·le go · :f:.J::om .F . to r·1g0 to GaO~ .i. 2 ~. ( ~olecu.les are aD> of the. sat:e type~ That· is; they a:i·.::: [c::.ll ·s clcct:r.·o.ti t· ' l . . h'..:...... ~., .... ("' :-: ...... :: SO they should have si~·~-; lar .spectra, . sir:uiar excited elcctr011iC: f V(..;. v .... ->.), .. ~ .... ,_, ; • ,. ,..!.i. : ·. i· .. .,· . ~' .. ' u:e: ::?ick, out the /coi·::esponding lO .C.1..2C-c:t·~~".:.~ . ~ : ~ . . . . electron :molecules. up to 15 electron molccnles. ; ~~~~~-~: -·' ... ~ ·. . ' ~ ,, ~ ' ; '~~ . .. 'r·: Enc:"e;:tcG o:· 0t~ct:r<:>~:t:rc 1,~V(':lc o:::. s;:.i::~ [e~::i..::e~c·(;O;l r::.al::;c;.tJ.:t'"2. ,:·.:· . . 1. '•·. ,;: ' . <' · iYl · th.::'A<.:.:;:li-:0.:~' c:Z' · ·,w:i.::·.;~"~-s-:J.::-~:Ct1 :r~:;1~ j. :v.: l<)~ 3 ) ., : ~: ~ .. :_) i ~ ·' )' ~ t ~ (. . ' c • • ~ -~ ' 3() ~ .i '~~~~; .. t1 ~- f ! ' .. ~ .IJ"i ... , .<• .) • .) ·.. • { ')fo:\: :.-;)' . 20.0 \-._ I•• _.- _, ,- ,.: ~··: J~CJ .. S1 ; ·, ·~ . . . \. . 6 .. -~-- '· ' .:~ .. l.~.' . -~- (.:.];~2) .· (-1~1) ' ,. '• ... ·.•. ._, ~+ :1 .. . ~ , . c:W : ::o .·> I ~ .,. ~- ______======·.. ~"'...:_.:. ___, ___ .... ______•_ .... _.. ~M .... -~ .. ...:.....-.-•• -~-·-..------: ___. _____ .. ; ..;. __ ~~-----·. ----,-·'---~---~-----·-----...,.----"' ... ·'. '':. '' ; :· ; i i•. •·{· i .~- ' j_. t> : ~ ' i-1, 'l i, ~: - -.~' '·' . ~ . .,, .- ,. . ·. ~. 1 ~; • ,, -' ,,. .-~ . ' . . ; -. ~ . { . /> .. ~ ~- . ·.:.' . ,. ~ ·' ...... "1 ., ·_\ . '. ~ • ~ : ' 'o • . ,.. .,,; t:. ·:·::·.·.:·· ;'.; ,'o!. ,I i ·.,,_ ., -~ ' .V . ~ .. :i :{ I .. ; ~ I I I '.\:.:' } I ' ( •' ~ J ,. I' :l ... ·. ~ 1 . • . ~ I ·, . .' ~· States relative to thc ground .state~ is generally_ ·., .. ; ; i:;·:round as one goc.;; .f'Tom. lighter ·to bee.. vier :::1.0lccules / ,·. '· i .·. . • ' .. . . \, 20 ?7 ,/ st.3.te has :cot been seen for t;he aJ.lr...aline.. ea~hs but it is lmmd··<'~,· .·, ...·' C and' lle have reason. to eXJ?cc".-; it 'be fou.:'ld near the energies ·" ::fo:... ~ cve1~ ·c.o .; .. -·"--··-·-·-····· ..2 . 1: "-~-----·--· --"'-~------... -~-:.:...... ~ . ·;: .,1 • 1 . '. .· . l •',i . ·indicated in Fig. 12. The hJ.ghest Z is known for. c and fo~ CaO. We just 2 - ~- : ·;ecently found a transition involving this state in a' spectrum3B,39 of MgO vThich has been lmown :for a long time. ·It was an extremely complicated spectrum. ~ ; ". :, j ·. ~. ~ ·~·· . . . : { ;It has been seen in flame·s, furnaces ·and arcs -almost any type of high ·~. '. ·'· ,temperature source containing magnesiu.'U. ·. The spectrum turned out :to be . v-ery , complicated because in the same ~3pectral region there ·are spectra due ·to MgH MgO, MgOR and possibly other things. I At least,·. those three molecules are . .j· " ~ .. •. well established.no"t-T. •· . ,,-; ' ~~ :: t .. ~. ·, ·.I T'ne spectrum was. so complicated t}:<.at it l·ias thought that it ) /. '; .. ·· :. ( > due .to L'lOlecules :1-Tith perhaps four or five atoms.· ,.tc_ hav-e been o."ble to .. ; __ !''' ·· i ,·:; shcvl by a:pplying the mass action 1a·w- and by isoto:pic (substitution thc.:t ell , the spectra ~~e:ce duc to molecules containi:r.g ·only one f.is ·'and only one 0 1 •· ·:!per L:olecu.le and that some or the spect:r.?.. 't-Tel~c also due 'to a molcculC: ·• · .. one R per molecule. Af'ter very hard to .. ·' ·~ <: 1 ~ontaining vi~rldng el~nate th~ • ;::r~ydroxido ·-·-.and ~t tu:rned OU;t to 'be a di:fficult problem: to exclude hydrogen .i~ufficiently to ra::>ke. the hyd:coxide spectru:n vanish we.were:.lcf't still· r ·!" : ~~ ·• · viith an extrenely complicated spectr'U:."l.7 . U>J?:i,Xl:rently. due to. many overlapping :·: !-- .-. -·~ spectra. ]'·' <·f: . . . . .i ::.·.:: : ; state, but :most ~of the spe ctrurc. is: still U:."'lrilulyzcd. :t.~d W; feel Cl,Uitc .. t· ' ,1 :•: • ,, . . ••. ' ''· ., 1 • '~ ;, that' the :remaining' spectrum is G.~e lo..~·cely to ·So. t:~cr~ is . ; . . . . . . / n:o lack of spectra to account :for the rr>.issinc; lc'v-els. It's just bcc.:n too ·difficult· s. ob to unravel the 6ve:dap:J?ing. spectra. .• 1 t '! '.1 . t '' ;-25.;. '~ ~ ! 'I; ,( ' ~ '1. ; 1 . ' . !.' .. 'j 1' The intermediate Z state has not been seen f'or c2 because of' a special •· 1 selection :rule that applies, to the homonuclear molecule c2. vle do see this Z • 1 •. i ' . ·,.,;' .. state· for the alkal~ne earths and it decreases in energy as·. the molecule .be.comes heavier .. :No 31T ~tates. have been definiteiy established ·f'or. CaO but there is '-,.J,i-. 4"' 1~4 ;··. ... a spectrum.... 4 ~ ••-1.J..' in' the orange ~·Thich I am quite, convcnced involves a ;)Tr· i .state.. \ole won't knov7 exactly where the triplet pi state is 1intil the ! . :J spectrU.>n is analyzed precisely, but it is. somewhere near 19,oo6 i-;avcnw'1~c1·s. · Like~:iise, othef'·unanalyzed spectra ri.re lr..novm •·rhich akost surely are ·.l' .. { ' · d~e to sorr~e o'f Jche other sta~es I·Thich have not been ob.served yet~ Hhcn one·, completely works. these spectra out a. lot more states will be knovm tho.:1 ' ~· . ( .I ' ·~. a1"'~ cataloged nm·T in the various compilations of electronic levels. ! ' . \ Custo:b.ariJ.y: liheri one calculates· tr_eJ."'liodynamic properties of: these r,l.Qlccule.s . . . . •' : . ' ~ . : ' \ 7..;. general prOcedure is to thumb tr~ough Herzter5's table/~of electro~ic :r. ·.! . ' . . .":·. . ·• ·,s-tates,' to stick all "the constan~t:.s into a computer and. 'to grind. out entre- ••. ; ·: ~ ~' j .,' ' . : . ' . , pies and. :free energy 'functions. Yo.u ca..."l find out pages and. pa(;es of ·: I . : ther;nocly:;:::~ic properties tabulated. :for>.ll of' these molecules over teJn.?era.- .~. ~ i ' ·~ ' . ' hc.s· .... ''•, i' . tu:re ranges o'f·thousands o'f degrees • .so it is obvious that. som~one r ( . :' : I. . ~ . j I ~ J I ·.:gone to a lot of Uil:'lecessary. vmrk vrhen 1·7e k..."10i-T there are all sort3 of levels ·' ~ ) · ' that they have neglcctcd; as they have .J?uJc in only the; ;:mes :lvhic~ juz~ ; . i .; . ; ::I . ~·. .• ,.l ~ ; I nappen to be obscr:/ed. ,i ·.' . ,•). ' . ,~ .. ' ' I~ l·re. "(Ti],.l see this nlOre ·. clearly 1-rhen i·Te consid~r: the 1 ~ i '., t 1·' cq~fiBUrations that affect the the'l-inodyna;·.uc properties: r.ost criticc:!.,lly.· . :,_: ~ ··,.\ ' • :' t. ), ; .'·; . . . ' .1 '1. ·T.n.e= lOivest conf'iguration yic;l.d.s ·only e. --l: Btate 1·7hich. ha.s been observed ·) .j{ . i\ ! ' ; fo~ e:.r.e::·y one o~ t.he molecules listed.,·~ T'ne next. coni'ugration ylc'ld.z a. 37T . : ~ '·.· . . ' ·.. ~ I : .. : ·1; ;, ~ 1 3 'J •:and· a 7T state. T'n~' i; state is e:·:pccted to be ~bove. t~e · ; stO.t~ acco::.·ui~-:;5 . • ... -. ... ,. l : . ' ~ ·. ·.'·· 73 .... .(..... '· /' ...... :to' Rund 's rules'):::_):tt is k."loivri~3· tor c ,: BeO) and MgO.. .An unresolved ini'r6.rcci , .. I; 2 ,' ' I; '· L ,, ·t. ' ; . ~ :· ' • 42 44 45 . . 1 . . . ' band system, ' '._ . of CaO which al.ID.ost surely invblVes th~: :IT state indicates •; • '< I~·: t -.-•;••. ;·••' ·.; . I ,_ ·i . ' 3'" \.1 ·' The ·. 7r state ;' -:· • I .. ., ·:Le~ ·us apply t!lc geie~alizatior:.s '.· i:J.olecules .. : He gencrally.. 'found that ·the ave1·ase enerfSJ of a conficu.ra"~ion . '~-- ' • j : -~- h"'i (7(-.::"J.-r-; ~...... o·..... -~.; ~:.1""'""''.'1+."'1 o·~ v"-·::' fell. off as· ive \·ient -".;o heavier r:1oiecules. The ...... -~~·-·.~ ;- J..o.--~~.,..:.-.... """"' ~- .... ·( \ ; ~ . : the a 1 1reline shmt t:h.is bcr..avio~. iJe nave clear, evidence ..., . . : . . l · .'., bcr..avior for ·t!'lc lO't·Test configm·atio::J.s i'rou the position o:f 71 of 1-;:go. . ~ -~. ·--:. l . i 1 .; · a.nO. the· .evidence fo::: . 7r of CaO is in agreern.c_nt. · '! 'i' . ·. . ' .~- .. ·on the other _:C..and the splitting of levels uhich is about. 7;0:)0 -:,.;ave- li.h.ibers generally does r..ot decrease very. rapip.ly in ;going to hcavic1· r1Qlecules; :> · .. ,j•\ :rou :;·lO·uld 'predict ·that ·the ..;Tf state \·li·ll. cross U.'!dcr the •' •' ·': 1 ; • · :z state for hea·..ric:~ molecules. ··.·. So, on the basis of this cm.~rcla:tion \·lC ·imuld p:ccdict 'that .contl~;.:.ry ; . :' .to all the taoulations.of :i ' . . ,. ·oef;Ti., ~ .. ti.11o bserved should 'Ca.ou~ ·: . nave; •. tea. . ' r ._anycrre .calculation using :tho;;;~;; ., !'>: ·•' l 'l r·,. ·at leas".; a facto:· of 10. . ·f' I ;· ~ . . \-!ell, ~01·7~ suppose you raise issue Hith m2 ~"l.d say, .· ... f ·is not gcing to be· the greo.t.n I 1-rill give you , ·I·;; ~ 1 ' _.;. f.· \·iS/\r~nl.lr.1.·bel s or so, .an~ -let ~'-s put~, tl'ie . .~Tr sti:l.te 1 000 ~.;a~enu:mbe·l~s O..LJo··:c · tl1t: .. 1 -i ! 1 :I ;~;z: st~te .. It has to be belcH the /T sta..:ce \·lhich is 3600 \ '. m~iy ~ ·' ., :• ' I : ' t ,. ~ . ·II! 1 \::above z for l-1;;0.' . It you are talking about a· system of 2, QOO ··' ". the: :;,·;,- _,:· .• i ' . • . \j . ::.,.·."'I~ \ i S_.~o.~p....:....!. i·lill deteltine the thel"l:"'~dyn.ar.1ic: :!_):;'O}?e:tties_, b~ C8..'l..i.SC -~·it i-lill hC.\TC · . ' ' ' ~; d.ifferGnce. in e::1c~·gy i·till giv<; :. f~ j ·t· I even is slightly aoove -.:.he therr...ody:namic :9ro!)crties o.1·.:: fi:·:e:.l 'by ..... '· the 2l"iT :state.· •. ..·\ . .'· ::' . .•': . .! : { ~ . -27.: ,,•' '·,· ! .· ·. ' ·. ,{I·) ' . . ~ .~ This is, perr.a:ps, a good illustration of the -caution. one must use .in . ' ,' 1·· ' ~: ' ( :::_~rying to ;pred:Lct the, entropies of high temperature. Di91ec~ies~ even-as. ' ._, .,1' ' .. : :; ' i· ; :''!simple as 'the:'diatmtic qnes. ·you just can not tal~e the particular infoi-.u.a-· \ ; . 1 : ; . ~ t • ·. ·-.~; .. ' tion 1vhich· :b.as been: tabulated· in tables of spectro~cop:i.c. data because they. . : .. ~~ ·. l : ~ ! ~ ~ are-generally incompiete. P~d as I said before, for the bulk of hi~~ ·_,·,,. '' , , ·.;temperature molecules you cannot even· be sure that you have the corrcc·t~ ground state. if yqu take-the lm·rest, obser..red state Hhich has been t:;.bulated. · J •. : ' ' ~ ' .~ '· . . I would like to just taJ.te ·a fe-vr minutes to indicate ·hm·T we. hope to ; ... . ~ ..; :·: ' ·1-. ·:~··~remedy this situation. One of' the m~thcds, of course) 'is :'to try to il-:tprove • •''j_i '·:' ·. \ :'· 'the transition r:ietat compounds. . All the simple disc~~ iOJ.+ I go. ve you . [ s f ,. ' t· .,' . r r · ' ~ ",; } ·' ·.:,these cases it coU:ld be·anything from: a doublet s~~~:tto an octet stn.tc7 ·!,. 1/! :·· .. l:·· '· . and cbviou~ly that is e;oing to T!c::\ke a trew..cndous · diff~rence in the the:x:r,.o- .~ . ' ~ ' ; dyna,rnic :.f>roperties. One of the· i."llpo:i:ta.nt tasks' that 't·lill have to be .tac~:l:;d ,, .,· .~ ,, I I '' .. ' ... ·I l ! '·it! I r ;· '! . -·. '· ~ . ' ! .. ~~bCfcil"'e ·1.tq can i-c:'l]1y .ma.ke any us<::ful pTcdictions about; r. '·· ' . ~- i'"'' .·. o"'':i..,v:ic""' ori :;;11c ··s:9e·~~C1.. ¢.. t.!:cse ··, ~ ~ ... {o,.i,. -- ot . . J' •.t ·';' t .. ;· Tesolved~ it, -is .·.·. ~·· .!. 1 ' '·, .<; ... :' .,· I •: - ., •' :,... • .. -.~ '..: ' ~CCJ.a.en-caJ...L.y. :usual..J...Y (jhe ·:~~~alize t,l-".!.a.t :-n.is. SarJ?le had half a d.oze~l e~:tra. cle~en~s.. >\·Then he \•rculd · ,;.· t-:,.. .·.~ru..'1 ·:it he ~·:o!ild ge.Jc a: beautiful ·s:Qe c.Jvl--u:I!.. ·chat ..c~nGd out bot to -::;e . d~c ·.~co . ' the .. rrcjor compo1iel1t bu·t due· to one of tlic inlJUl... it'icS~: ~- ft_ftcl.. so:.:.8 ii1"v,.csti- •••~1," r· .. -···· '· .r ' ~~g"a.·.Jc,ion;· the source .of th·~ ..spcct~ ... l'll.1 t·la.s: eSt2.0lished arid· ~-.re · :l:.~d a. li ttlc ·r.:o::... e "' '' ,azta. 1 ~ .l': ihese ';::boUt ··.·' ,. visitiiJ.G Be:i·k~ley ra.cen·cly. f':com: Gtocl:J.1olru a:..-;.d he: :'~rt.s . ' SlJC qtra _t:r~ ..:c; .loo:·:cd too \·rel~c .. j~l_st r B:e \·las 'loo2dng t.hrouj.1. :his files of pho}o~~-iphic ~)l.~tC:s fo:t , S'o:-::ething else and hap:yened. b notice a pertu:d.Jation on a pktd. '· pertur'baJcion of the rig..'lJ.t tY?e is a ... : . ) 1 ::so he. i:n.":1.8diately forgot about. the ~olec~~le he ·r,, oeen pretty much hi·!; ;or. !:llSS. ti.nd~ if 1·7€: ·. 8.::."0 G9ing ' "t ~.. i : . . ' :. ! .. , .• ··~ .i:·r·~,ou.~t-.cz-- d~te:..\·;'e "~~e·d, .v;re a;"'0-"_goi:lg(_:-~o ha,rq-~o, go a"pOut i·t ~;;~.r::;~0:~:::J.tlcc.-llj,..~ ;· : . . . -~ . ·c . . •:- •. . • ,. , ' ··;: -;-c ~~~ t'.~~~~~~e.~~~~=~~~-.~.~~~--;-~~~~C£~~~~~:~t~~~~-~}1?i. <, \' ,. ·.. . ~- ~ ' • 'I~. '-'• .-::" '•' . ··:. '1' . ' ':,.' .\. ,; -'.... ; \'" ,'•' . :- '.' -~ ... f.·' . ~- ' '. ',;. <.: f ~ . ::; ~ ! 1 ~-~. i .. · ... . 1 '. ,, . <' /. ~.-l .: .> ', ; •" ·' . ' . ·, ·:·~ ' i~ ~- ' ..,. ; r ,. ~ . . ~ .. ~- i '· .. . ~-· ·. .;.:: ·:1 -~-~(·: •,· 'f, ...... ~ ;_ ' ... ;: i . ;: . : ·.·: i. . ' ~ ' .-1 i~ !< ... • • : ~ !. . -~ :' .:' :d ;··.·· i .; .;r~he electric .re\~onance. meie~u:u?.r be~ me.thod, '6ptic~lfspectra' of' molecular: .. • :i [;()Wl . . .: :' ... ' , ·.. . · .· · . i . ... · · 1.. • ·• ; { · .>.: · ·bea.nis or the matrix method .. : · · 1 i · :•. ·· .·. i ·i , ·~· .. ::'\j:. ~e-·mat~ix -~soJti~~ ~t~~d.),~>dffers the possibility of s~udy of'·: · ' . t ~: <- j . .; ',; . : ., ·. ~. . There are many complications, but· th~ method also .oi'fers the possibility· ,'.of nia.king i'orbidd~n transitions more strongly allo'i-Ted. ·· · \le often kno-vr the· . i . ·' _f· .. '.. , •relative energies of the various singlet systems· and .the various triplet . :: ··:· .systems but~.not their rela:tion to one another. The hope is that perhaps . >. 'in Iiiatrixes we tvill see intercombinations of' singlets and triplets; .; .·)· ; :::: . ·: ·, 'they may be displaced a bit so that 1-ie may not be able to use the:··results · . . . ' . \; . ; • ; ; i for accurate thermodytia.mic properties, but they may be clo'se enough to c f. •.' . : ~' ' . ' ~ _. .. ' . , .: : ; :the gas values so that ·i.te would knovr.vrhere to look in: the _gas spectrum ·,·- '·r·-for:\ these weak bands~ · The trouble with ~st high temperatU:X.e spectra is : ...\ ,. · that there is too much to look at and it's too confusing if you have no '• . " ~ ... :.. ; ·' {'·; •• :• .... J•-· _; ]; .. ,·J · clue .as to where it niight be valuable to look . It is: ••orthwhile to spend . ~~ . ' ·' .· . ·.·.:some effort concentrating on a regiori if the position o:f' a desired band: 1 1 1 1 .:: . · . \ ; ;~s kno-vm vTithin 1000 cm-1 ·'' . ~;;. .• ·'·' 'i i j · One interesting example of a :forbidden transi recently ·. ·~ L~; J! ti~~ observ~i·{~}' .. ~. ~ ~1 L; ...... : r ;~ ! .1·.· ; ::;~t Berkeley is the vibration spectrum of 1;he · s molecyle. \.:fe have .been i ,: ·, -~ '. ~ . .: ' . . . . . : . . ' '!(! 2 ·' • • !. • 1 ;:':\~tudying.variouSdiatomic molecul~s ~~hich ·have·. been·:,6~ndensed at liquid 1 .t. 7 ' ~ \ • .( ' : . . .. ;. r . + . ~ • . i .· . , .. .'hydrogen' L. temperatures. . . : in matrixes .of ~nitrogen or rare gases, where the matrix .·:.; .,. . ; .~ ' • '~is put in to' prevent the high tempera tul~e molecules from combining ~lith j ~ : ' • • • • • • •.. • ' .. ~· : :·'< ;?ne another. In this manner the ~2molq~ule has been: isolated and the I• •. ·.J . . •.' • ',·· ' . . ' ' <~ibration spectrUm. :is seen. ±t is forbidden for hooo~uclear molecules·, but, ' ~. 1 ' . . ; ~- : : . 't\ : ·'. .r ~J ., .)' ,". ·.'. ' ·~everthele,ss,· the matri..."{ introduces 'enough asymmetry:.:~O break dmm the : .. : .· This· bas its orgin in ihe phenomenon has been seen .. (~rohibi tion~ wh~ch ~- H: ., .~: ' ~ .. ':; ··i' ·-·------·------' > : . ! ,•t • ~ . . . ':~30- ,, I ':t ~ . ; : . ;i :. : . . .j I 1. i ~. \ ~: '·. ' ': it ' \_48 ,...' •'i previously ill' gaseous ·oxygen .. In gaseous oxygen at high enough pressure·.,,r· . ·' . '-· f: ; l:J this forbidd~n •vibrational-transi t~~n is se~n due -.~ .the: asyroinetry which · .. 't! :i-. . •• ; ' . .' ; , . ~ ·' .·,·; ' is. intr'oduced by the neighbors. ~· It is our hope that the_: m9:trix technique ..... ,! ·:.· ' ( may· yield more :infox'ma:tion o:n . forbidden transitimi~·· :and ·on unobserved . · {._ '···' i:' ' .• '; j' i '·~ ~. : .:;_<·: i levels~ ' ( f .;_l' i ...... 1 ~ ·.. : ·: . · i:; One ·of the· other techniques i-Thich looks ve_r; valuable is the com- . ·." ' ~ l. " :. _,· .. : .. ·.n:· _· ' . ' . .. I. ~ :bination,o:t: lasers w:i.th molecu~r beams, Part of·otir p~oblein .is that·.the ...... ,. I. . ~ . . ' ; . . ~ . 't'>spectraare.too complex. If we could tickle a 'molecule with a· la'ser so . . ;:'',,:::as to excit~ only one ·state and .then look at the flu,orescence; \•Te i-TOuld ( ,'v,. i '.:;have much sim.Pi~r spectra. That has been done in the Pl3..st. for iodine ' .. . I ' :~:\using .a. mercury •lirie to. excite . single rotational • lerv~ls of the iodine ·· 'I \ •' ·:·,. ; .· . r:: . \4 .·_ .. ·· .. ·. · .. ~ a, ~ . : ;; ; molecule • ·,~/ Vle h8.ve carried similar experiments ivith static 1 vapor I: 2 f. ·j 'and i-Ti th .molecular pe~ of' r 2 and. ,h$-ve. measured:~+ the .. rate of ·.\'I. . . , : ; . . ·':;'radiative. decay ·of the excited ·iodine molecule;. which. is half 'decayed in I· '• .1' ' ' ~ ) : .., ,}i . ~7 ·. ' • . ,I .· ' .·. '' ...; ' I n; :.. :. :10 se.co;nds .. ~This :is a very important high temperature'. 'problem with . . .' I . ... ~ .:_.\ ,·.. ., ·~ y. 'I ,\_ ;can't get by with the. classical methods::i·Te have used: in the past. High ;' ' ~ i •·. 1''1., ;,.; ' ' ~ . :''X I' \ ·:- !speed computers and :,automatic ·measuring devices will! hel:i?; · An, example' ~ J • } . l ·':. ' " ! . :of a nevr :technique is the use of polarization spectra, that is' to use' ; ~·. 1 ! ' ~ :' • • : : ' ' . ' ~- ' ' polarized light for .exciting. spectra. .. If an \mana.lyzed spectrUm. is due ; . ~: I .. ; '; i. . · t, ·, t (•,' ;to a. l:-1I :transition with Q. branc~es} the Q branches. will be more . strongly . i ·. · . · . I ' ' : ' : ..... ' 'polarized :than R branche~~.}';'_and: in' :that ivay one ca~[ det~rmine~ qualitatively ·i j ~ ~ ' '' ·,;. .{ ' ' ; .. : ;: ') . ! ~ . .. ·' ·:rl.1.':t,·· ... ;•... : .... • :! ,the type ~of· transi tio:o.;; •-·· .· . : ;_,~ .. ·. ,', ; ~-: , , ,'· ~-. :; • ;l: ·•. >. ·} ·... ·~-~.. ~ ·~! ...·, .,,. '' ·' ·' ';'~ .. " :~ '.: .. , ... •' ,·.· '• ·~ . . ''i ,. I • ·. ~ i. . '· :! -31-: '( ... ~ 1'. ;". ! .. .,( ·rt is·gqing·to take a whole variety 61' new tools to obtain the . ·~'· ~ . .. ' ~. ~ ' r. i necessary in:fbrmation:. · I think people. are going to! have to really use their . .i out for every one of these' nevr tools to make· the· . ' ' .. sort of progress that is going t~ be needed to tackle the problem of ',· let alone the 'tremendously impo~_ant problems of ''· ·i: \ ;: 1 tri<;~-tomic, tetratomic and the· vastly more complex· m.Ol.ecules that vTe ~ -~ 1 '', .. • ~ . ' I ·, ";:: find in these hlgb. temperature sys'tel!lS. ·If you ,e.xani.ine'.,the (rifficulties· l: that I just ou.tlined only .for. the diatom.c· molecules. it·;is clear that \,. I' '· ~ ~' . ·• ·T; .high temperature systems are .going ·to :off-er :tornudci.ble problems for very, ' ; . ~· '~ '. ~ t ' ~: ~ i :. ;~: I'~' ·, very many decades to come. ;_ ._; '(Appl.S.use ): ! :· .·.· ~ . . _,. ., : ·,· ·,,' .!. .,·· ··,. ,.·.!:, ,.' j' .· ;\ . ~-! . ·,.·,: .. \' j· ,;. ,.. ~ ,: : . ·,:• !- j . t ;\ ... i. ··:. i·. .; . ,~ ''/ ·.·.-=· · :·· -;·· .( •:.· .'. -~· . ~· .. .. : . ·;· ;., .• . ·, .: . · ..... ·· .. . : ~ ··.: . ~ " ' . 'l. ·.:..: ·., _·.·· '_.;'· ,, ' \ 'i ..· . :.:· ... -:··; .. .. : i '·' .,.· )'' .',·_ ~ ·' ',· .,• ~. ...., •. '. .:.·· ···, ;; 'r·. . . ~ ~ . ~ .. ·. :j> ..l• ·.. ; y;· ~j :. \'. >· ·:~ •.? -~ :; ' . ~ 1 ~: ... , . . • i • '·~ \ . . •• ... . ' '~; ,. ! ., l"' :'' I. .... -~ . 'J.,,' .:\ ( .· ". ~- ·. -:- .. . . ' ~ . I" :I : i. \ '• -32.:.. . ' T.. ' . ' DR. MILLIGAN: It. b.B.s been suggested· that·. we ·~ei.ke a· 10-minute . ; .· ~- r > '. Lrecess before the discussion starts,• so we will reconvene' in lO·minutes f !-.• ): ..: ' ~ ~ . . ; . "" t· , , ' . . '·· , ... ~ . I . • ~- ( rfor the discussion. ·: ·.· · ~ 1 .: · : • • . : ~ . I t; . . . . , .. . · · . -~ :_.; {. ... t • ~ I . ,',•'' " •, ., '·. I> ''•\ ·,·,·' i : ' ·~ . (Recess taken.) ' F .· .. ' . DR.' M:p:,r;IGAN: · If I .might have your attention, :we v_oul,d. like to 'i ·. ·1 .: •• 1 ~ •. ~·,(continue ~it~ the discussion now 1 please·'' ., . . . · .. ' . · .: .:; ;~ .·:. : ... We are_nowready to begin the discussion· section of the excellent . : ..···.'· ';_: ; . ; :. ::,paper that you have just heard. before- the recess·, and to'_starl this off ' > !:t > ' ; • \. : • > ' • ~ • c • • ' [ . • < • ' ~. . .: l < . . ·' . ·. . . . -~ ' . -: . ' l . . ~ . . . ·: ':·I would like to introduce ·the two discussion ·leaders ;who will take an ' ·. ' ' .. f: . . ·...... ·: . . .. • • ·. (. . ' rr. R6chow-·~ would you come forWard, please? '-~ • t ·._;_·;·: ·. .:; •.. :i '.· ., 4 .· . ~ . r } DR. ROCHOW: (HarV:ard University, Cambridge, MS.ssachusetts) .Thank 't: ( "; . , ' 'you, D.::r~ Yilligan. . . . ,, i · ·, ,. ".1-- ·.;,' . '·i. . . ·. . ' . . : )",.' i .. ;. I am sure this high temperature chemistry come~ :to:me:, all of' us •.. -~ i- • . ' .. '.,~ ., ·,· , : :-~;but for ·different .reasons . and at. different ti:mes. _For me. it ~<·ir~t strilck -.. ~ L 'j ·.home when I attempted to measure :conductivity of pure aluminumo.:dde and ... , ' , _; 'pure magnesiu.m. -:•xide and found to my great surprise t..hat tl:l~ .:;onductivity .. I ' f changed vJ:ieni pumped out t~1e system, that is, removea the ai:: and necess.:.._ ,) : <;. ) . aril:y the' adsorbe.d vxygen. It:· appeared that oxygen ~~as in eq,uilibrium • I P: :r: .~ .. :· ...... :,·, r·. I ' . . ) ~ . .. '~ ·' . Wit!: aluminum OX:'..:ie at. Very moderate. temperatures 1 . arid remembering the old ; ...... · .. : . ., . . \ ·. ' - . ., . . . i .· . •." ~\ . :saw tb;;"'~ the . .;;::p.ilibrium oxygen pressure above Al C· ..~ ;should be! something··, -~ -~ '\ '. 2 -~ ' . . . ' .... r '1, . ~. like: a, q~arter of aJ: atom .. of oxygen. per univers~, i-G !s·.... rprised(me that ' . ' •'.! .· , :one cm.ll'::.>· ·~:.:b:leea.,.' alter the conduc~ivity· just by ~ingaway, what ' ~ ... ·., 1 (' . ' ,, . i seemed to be ·ex't-.:4 oxygen. ·· }: .. , I ·., .;1 '. -33- ' ' ~ .· t. ~ • l . t. .,..; The ·point of all this is/ of course, that the conclusions reached ·~ : t . -: . ' i ~ . ·' . ' l .by extrapolAting thermodynamic data obtained at room temperature or near ,··.·'!. , .. '' l. ·. . . '<'there is a very unwise and unsure process .. It leads to absurd conclusions, .. ~ . . .. • ~ ' I I . ! . ·. ·~ ,. , ..· :. readily disproved by the simple experiment that· I had to perform. There- . '\· .. i. .· . . . . ' . , .... , . · :.; ._;fore; it was with deep p~rsonal sympathy that I heard Dr • .Brewer .expound : I .·::·t • ,' < • ' , ' ' • •• ' • ' ... . :. '·.'on the necessity, for acquiring thermodynamic information at the actual : ·' .· . . . . .: \ :high temperatures where we intended to use such information. ·.. ;,., ' i ~. . I . My question is a very brief·. one. I would· like . to ask Dr~· Brewer · • • ~ .j • '',i. : '' 'what he thinks the possibilities are of examining .the; nature of molecular , :;: ' ' .... ·.--:. ;, .. ' species or ionic species' at high temperatures. by use: of a solvent. technique, I ··' ... '·· ',' ', l ·: . : ,·:;>~let Us say nonaqueous solvents Operatirig in the range, of 800 to 1 1 000 . 1' .. /aegrees,' such as us:!ng molten silicates, molten chlorates; carbonate13, and . •.i. . : . ~' : . .·j J~ . i .:so on, and extending the :present information about electrode behaviors ' ' . . ~ ' .. 'L i .. ',. i .·· 1,: .. ! ··in sUch dilUte ··solutioris? .. ':1 .. DR. BREWER: . Although the \example ':i: gave here was for gas~ous systems 1 ·.: ~ . . l l ~. ( .. · ... ;· ~ : :1, .•. ,··; . ; l: : .· l l l ·. ·. ,:; .; the. same :principles apply, of course, to the cot;~.densed. phases; And for. : f . • : the same reasons, you will find. that as you go to liquid. at high .. l ~';•; ., ·. . ' . . . . . solution~' ' ' . ; j. ;; J:: !; lpwer ()Xidation states that don't. normally occur at .lower 'temperatur~s. in· •.· I .·-~~ : .. ·; J .:·· : · M.n_y of these. solvent's • · Liquid metals are also interesting solvents at : !' 1 , :. h:i..gh temperature.s. Many years ago I had the. task of :s'e.lecting a .molten ,,., .· ! ·...... ·;,· i. ~; ·-~! _; '; ~ . ... \. '· ;> ·.: metal.solvent inwhich metal ox1.des 1 nitrides, and hydrides could be de- ; :.;•::·~brilposed with a xriinilnum. loss of metal~ .. Thermodynamic. ~alculatioris ·and ex- ._: . •. I · · periments showed· that: liquid platinum was ari adni.irable solvent· fo.r: such. '-1 . t '. J : ·, J . . •.. '.' . . . • ·. ·';, ' : ~ ' . •. ·; . L\1 ~eactions~._.?~' I ,..c~ this is, indeed; a very :t>ruitfu~: field; andwhat's ·/ ·1' ·~ ·~; ?p.ore, one truit ~st: be investigated if, one is to be abie t? predict 'chemi- .-? .:; ·,: ' t' :· ;J 'I : ' . . . . • ' . .; . '' ·t l : '~- \ :cal behavior. in a.D,y-: of those solvents.· ·.. , ..• · ··: !; l .; . . i' ' . '. . . ·: ~~ t. ' ··.: } i ; ,. ~J f. :', ; : .. ,. '· '; .. . : : 'i . ' ...... ·------.. ----·-·-·------·------·--· '.; :,;:: ' 34 ·,'i.· !• • ; • 1 ;. ;: l i: ~- ..- l... ' . ; .• . .. ' . '~; l • ~. ; .·l ..• :·: Jli . For example, consider alumina that You juSt mentioned. know W~ _,< . . ,"• ) l ·l.; jJ; ~hat all of th;~s? materi~ have a_ fini~e range in ~C:mpo~ition. In · i :··.: '::ii f'act 1 thermod~amics requires that they cannot hav~ a sharp composition . ·.:·· . . ·,··: . ' ' . . . . . t ·.L· ~~~~:~ . . ·. .\ . . . ·. ·' . ·~xcept ata few· singular points ~ike' the absolute zero; fc;>r example. I . .. d .' ·~ the treatment of the composition as_ a variable. is of utmost· ' I ·.·There will be a different composition of aluminum oxide ' .... ·, '· . ' •. for each parliai pre~sure of oxygen although the range of compositions ;.. ' ., · .. ·," : .: i :Will be close to three oxygen .. to.·two.' aluminum. : }' ,·1 .. , '' -.:J ' ;: ~· . ~ . i In the particular case of alumina~ ~t is possible at around 2000°K ., .. :-·:.-/, • I .·! [:' ,,yto get equilibrium partial pressures of oxygen anywhere from. 10 atmos- '•. ,· ,.pheres of~xygen to J.,cf:¥ atmospheres of oxygen*·:The composition· !'·i·! ·:~· · L., :.:'·'remains clo~e to·~03 but must vary •. Varying the. composition from 1.50':to·:·, ' :~ c;-..:~ 1-ma._!ls'~j1.47 is enough to change the oxygen partial l?ressu:;e by at ·least a ' . ·.·.•··. ,. :: . 1: .... ' . ! . • ' . ' . ' ...... • ~ . . • • "i '·., r· . ·~ factor. of several billion. It is extremely import~~ t~ recognize the. ~ ': I t ·. ' .! ; '· ~:,:important role of. composition in fixing the·· thermod~amic· properties •. , :· f· .I,, : • l ~, ' , , ' 1 • ! I ; . • ~ \}: .. <'i·· ...... ; :·; -~ :' ;; ! . .~· \ . ~', ) .: . ! ! DR. ROCHOWi · Thank you. ·: '• . ·; :; ' '. ~ :' ': '; f;! i.' , DR. ROCHOW:. Dr. Sisler, do you have a questioil'you· want to ask ' . I, ~ I '. : ' . . ' ' . .: ::~before. we. come to the general discussion? : ·: :.; >ll~; ' .' ;. .: ' \ .. .•; . :.. :>;ji DR. SISLER: · (University of Florida, Gainesville:' Fl6rida) I have· . !"' ' . f~ •'' ,·.: ''.:co~ to the conclusion that my .presence as a discussion leader 'tor this· 1 1 ,. ~. . . ' ,, . 1 ... • · '· , [:;:~;;chemistry 1 'from .the; area ·or my own1 research interests.: . . .. ,~; 1 .-~'~·JI'·l ', , ;, 1 ':.~ ~-·.' •:·.· .. ·' , .'· ·.,, , :.:·· "·' .. -. ; .. •· ~ :-.·::)!; However,·! thfuk that we should[say that even for: one as far afield i 1.· . " ; : ;: . ·.. · . . : ·•:' : . - : . ' . . : .' • ; i '. . :c . . ' .· ; ' . '; ' '. j ·. _;~. : :, ~ H'as I am from the area of discussion;' one must be impresseq by the ' :;, ' 1.. ~.•. !.~.r.·,:·: . .,, ~:·~ . ·-~;· -~ ;·~.: .!:!--~: ~ . .=~:\ u' •. ·~~' ', '' ·.:. :~ : ~- ; .. ~'- . : • . . ,!·: i :; ;(:. ~. '·~ ·.... ,., r .. ~ :.-:_~;_· .. ,( '· 1~: ·":.;:· :-',-t._.t .... ~. :. : . ~ ,. . ;·,·. . :·~ t -·, ~. .. . ' ' : ' . ~-. !' ' . ,. . ' ~ ·. ' ; } ...- . ''· . i . .. ~ . '. ', .. . ': ' '' ' ' ·,, ·~. ·,' .. 35- . t~ ·.,.:, . .,· ...... '·' l ·' ·.._. ', ,· ' ·~ . ! , ~' · ; , , . . •, , ' .I , '., : , · ,. , · , ' . · · · • r • • ~ • , · .: ·~ ~xceedingly'lucid:a.nd inspiri~g natur.e. of the discussion which i.re have just , .: . ' .. ;:. ~d~· I think Professor Bre1-rer is; to !be highly' congra~hated on· the .very .:; ~ . . ,; .·.·.·. ~.~ i.· ~i.·:.~~: M L i. \ ~ : . '' ; j.; ;,:fine presentation whi.ch he has given us. , ·.• l r !Ji.:;:f;l'. i . . ··.~~. ,; I ~~ j < ~:~:i Fl2.ving sai~ t~at~. I vTOuld exhibi,t my o-vm naivete; in ~~is particular area 1. ·.· .• :·1.: ~ •' ~ . ; ! ; ::;;by asking ~ihat are pr.oba'bly 'two very stupid questions! . ' ·. , .. , I;;: , ,: ' i ::.:l· l . One, .~n the presentation of ,techniques vlhich are ~available' to the ;.:researcher in the field of high temperature chemistry vrith. respect to •1 i·<, . . . • . , .•' ~! I • ' ~ . • i , . • ; ;... : ·:':·~structure determination,· I noticed ~thB.t Professo:r Brei·i'er did not mention ~-· ; . .~~~ ; . . ~ . ' . ' . \\ i ' ·: ··the method ·of electron diffraction. :And. I am just 1mndering, is it possible, ·. ·, : i .. i·' . ·;.·· .. ; ;~. l • I < i ·. : · does he think, in any i-tay to develop .this technique and adapt it to systems '. \ · • .·i, I :) . ' >'at high temperature? Th:i.s is the first questionl . ~ f '' ,. ' ' { The· second one is a very minor one. t 'I '·.: ·.• i :·.:of his ·slides and I am just lvondering if. there has b~~~ ari.y discussion of ' •• • • • • 'lJ ... ·. i'-.t';! ~ ~ :;.·~the' struCt~e·:. a·~- ~his particular spe.c.ies 1 · : . • ' : ' 1\ ' . . ~ :· ., '·'-'. . r ; ''; ;. ·. Dr. Erevter:; .In 'ans-v;er' to your ~irst question,. ~he· principle of e.lectx:on ; :·:<:·diffractio~ would be applicable, but it .would be ,;ecy 'difficult' to apply to . ,, :. ·~: '.,.:~·; ~ . . ~: ~ . i ~ ,i . ' . f ; . • . ! ~ :.-:t •, ,.; .. , , · ,;the problem of d~termining the. structure of Mo o , ~o~ ex~mple ~ , As a Ill.f. tter I· 9 1 3 ' .. , , ;:'o f fact, 'Akishin and his associ~tes 2 ?',~l have a high temperature electron. ( j' . r ··,.; :.:1 ' y;: :::a.:iffraction unit whit::h they have used recently to determine 'the structures of '·t ·' '> i · . :. ji J:the alkaline earth dihalides ivhich they .have reported 'to be linear.·· ·But J\ ·: .. ,. ;~;rofessor Kle~~~~; ~nd his gr~up 19 ~ve found. b; t~~· .mol~.cular beam.• electric 1 ··: • 1 ·::r~sonance method .thai the' bariUin dihalide have dipole' ·mom~nt~ and are bent.· .' ; ,: l ' 'l ~ t • • ·, -:. I ': • .; ; ' • ;;. ' •. !!' .'1 • I • ·;. ' ' ~ ' ( • i f • " ; • • • ·_ ! , • , . , •·,: • : ·if : ;; ::)f' the.re ,is' question E,!.bout ;results for triatomiT mo~eq~les possibly due to ' . : ..~ I . ;{ ;,~ :. .· • . . . . , . ; ·d ;. .: ·.: ~rge amplittJ.des.o:(vibration{9rie can'ex:pect d:iffic~ities idth complex molec..;_les ' ~ ~ ' ,, ~t the high temperi.tures 'i·lh:i.ch 'impose. ~~m~ serioJs' pr~blems ~ . '~ . , ; : :J.; :~I· Dr. ;'Sisler: ; ·~{~11~· ·I: wa~··t~~~ki~~ .in term~ ~~r;· t~d~gs,iike c o and Si 0 .! .• · :··;;· . ,. 2 2 2 2 ; ·•· ..;; ~; ! .. ~ . . .. · ... ·;~. ··.:·_.-··J·· ~ .. ~. _.. . :~: ~ ..:~ ~· r. . ' ' . ) ·. j :• '',and ·things: of that sort •. ' .... ( <: ,. : ·' ~· i,. :' ;: ['. : ' . .·· ' ~· j 1 '.)·: . ,: i . \·, .. ' ~. ,. I! :,1 ...\ . '' ·. j .·,,, ..1· ':.'' -36- i -~ ' ;.; i . ·., •.· \ i •. ,· t DR. BREWER:· That's' even more difficult than the triatomic one I I "c-,.,; t i. . .~:1 ·. . ' .· just cited, if you take something lfke Si 0 • · Simon · , ~ ; . )\!i· 2 2 .Pi-of~ssor Baue~Y : t .•; , . ~ .-· •. < :(! ' I • ( · ~ ' .•. 'at Cornell has .a unit under construction which looki'pre~ty promising. I •·' ~. ; ~; ' ' ~. . . j· . •! •• )· . -~ ' might say at the moment it hasn tt really proved itself for very high temp- ' .·' I . . . .; . ~ .; ,.. _ ~ ; ·; · ·:\ eratures; ·but I· am sure it vrill be .useful for some of: the simpler mole.;. ., ~~ ' : . .: ,; : a.riy 1 cules .. We ~ill certa:I.Iily call upon· it be'cause we don~t have choice; I 'l • ~_;:., :·- ;-· .. , ~:; Now, in answer to your other question on cuprous chloride 1 Norman '· ' :~·~·:.)Lofgren and ~riginally established the fact that. cuprous chloride was .. ' ~ . ' . ~: .. : ; . ' ' ~;. . ., _, ·.> · ;;: trimerized by studying the equilibriunt between solid· copper and a gaseous ., 'i . ~ : _: ~ . " . i ·(; ~ ' . (' " · (:mixture, of HCl and hYdrogen. · We varied· _the· ratiO of :hydrogen to HC~ and .; I :. ::>found that the.. mass .action law fixed the major gase~~s .s~ecies: as cu c1 • r 3 3 : -~ ; ,. 'ti; . . ' . ' , ::our ~esults~indicated that the entropy of eu c1 was.very low. On that ! . . . 3 3 , basis we postulated :that it would be a cyclic structure of alternate copper ~. L .e. . i. · j and chlorine atoms~ 'There have been two subsequent investigations. A . ~ . i :ma.ss spectrometer· irlvestigatioW~onfirmed that cupr~us chloride is largely, ~---' :f. .... ;cu ci , although there are small amounts of tetramer~ · An electron diffrac- · •· . 3 3 ' \r:.t:./ ' ; ~ ' · ;· .)_ 1:: 'tion me?-surementV indicated that a' ~ckered six-membered ring is a plausible · · . i i ' ' . ~ ~ ·.. ~ : . .\' . ' . . . '' · · · · .. structure. So things seem to fit pretty well. ; :: . . , ·i . ,. l ~- . There is one queer aspect of the mass spectromeier work. ;When cu c1 3 3 : ·. :::; ''·L.is· hit ~ith an ~le.ctrori,· the major ~reduction is eu;.~ When that was :t,! ·...... , !::., ;: ' . ). . originally obs~rved, ~· it was assumed· the structure would consist of three , . . ' ' ';,< '.; copper atoms bonded together with a chlorine on .each copper. However, the. '; ; ·,' \ ~-. r. , . . . .' .: . . .. : ,· ',.' i.'' .·>:electron dif~raction work; which indicated the six-membered ring,. showed ~ • : I .~. /a very large. amplitude of Vibration :lrith the three copper< atoms coming ~' ·, ; ~ L i • ' ' ' . . ' ' ' '. ' ' , ' l i :' }'', ' . . ,• ; .! .:·together' for a considerable fractio:Ii of time~ Therefore/:. there is a great. ~ ~ ·;; ;.: ; . '' :. ' . ·.. \ ·, ,. .._ ..,. '". : ·.• .... , ,. 1 •• -"-'· ·. ~- . ,.·. " -~ .. . .. ' ,,· :I .' ! . . ____ . ___ .. ______' '' _1·:. . t : ~; ' -37- ' . . ,· ;: __ . ~ . :. ,',. :· ·;; ·.: ·:' i. ! . ·.:;probability .that an electron will knock off the chlorines and leave t~e .,, l ··! . ' 1 ·'· ·. :1 1 '· ; : · ;~'three· coppers ;bonded together •.· · ,, ' 1 ;. ':· : ~-· ~ ' . DR. ROCHOW: Now it'is time to· begin the general' discussion, and to ",I .,.·_' ·':have your questions :t'rom the· :t'loor.,: . ! :.·' ·: . ' • ' ' J .. Matters went so well this morning, I hope w~ can f'ollow the same plan: : -~ j . ; ·~ ·.', l '.that is~ if you will get up and give your' name and address .yQur: qu,estion·: ~- . ~ ·-·:·\ -· ~ . . '· i 'to the speaker 1 we will try to recognize· each of' yoU:· in turn and give you ;il ,. ~ . . •· ; , · :·. :au a chance. If' you pref'er to write out your· question, please do so. Dr. Sisler ' ·,.; ~: t i ! •-'i ·~.:can pick up the questions or you :can direct them to me. ! i;' Yes, Professor Cotton. ·J' ' ~ ; I ~ -~ . DR. COTTON: (Massachusetts.Institute of Technology, Cambridge, Mass.) ' ~ . l ;;, .that the state of' is kind of well and I think ~ow gr~und c2 esta~lished :;t,;. . . ·...... : . '· . '·,. · ;: that t .E is definite, what about B ? .. Is there anything ne~ on that? . . : ~: i . ' . . 2 . . ; I , ~ . •: . ~ ·• DR •. BREWER: I think the molecular.orbital correlations f'or B would . .;:~; 2 , • ' j'' ' ' . . • ·, :~:be clear enough. B ' }las s:l.x ele·ctrons to put in. r' :thiDk the correlations . 2 . .' ' 'i \ • ' t l f ~ ; ~ i. i ' ~ . . ·. . . . • . ~ ·. . . . ; ';W:l.th molecules of th.is type will allow us to. predict .the ground state. '' \. I I ' , ~ t ), . , ' ' ' ·' ,•, ' . ' '' \' DR. COTTON: You don't think there .is any probi~m about the other . ' '·· j>i:i. ' ' .. ·: . '. :· ··' ,; 'sigma. state? ·' :. f ·,. . ' • ' i ,, · r .· _< . ~:r~ 1 DR.· ROCHOW:' .Could you please use the microphone, Dr:. Cotton, so we , ~ ' , I ~ 1 ·; ~ ! ' : .hear· up here? ,. ':': . . '. DR. BREWER: · If' someone could pass one of' the slides, I think I could ~ ' ;.. . ,' ' · ; ·' ·.. (' DR.;': C..OTTON: .. I had the impre. ss io. n wh. ich may be'' .entirely erron.. eous ,. ' I ~ ll> '>j ! 1 _.;·.; ;· <;~;-; . ·, ' ~ .; :; :::;~hat there' was some question here. also as ti::; whether. ~he third sigma. ' -· ,. . " ' ' ·. I ',I . < • . ;:~t6rbita.l was inthe··vicinity of 'tb:e' :Pi orbitais, ~d th~t:.tha.t ~ight. have '.,:;·i:1r:;- -·_. - _._ -> .. '.;·-·:·· __ :; ... ;7:. -· /-. ~--. ·.-.. --: ::.·-·, r :·~ -L -_ :::·>-1- ~------{~ ~~ -.:,: .. ~, - r ··;\:contused· the· issue~ · ·•· ·.· ~·· :·r · ·:. ·· · ·. " ~~ .. ·t:, .. ;_ .. .-' " ·)::.-:·~_;.~ (:;' ~~-~-: ;f_.··r:! \. ' ~~- ' ; ; -·i ·.. =: ·.• ~. -,.: .. ·_: • ~ ·. :.-~- . ' · ..", · . .t • '·-· -: t·' . ·;::: '; _, -~- 't . --~ \.. <:~. \:;·.. ~ _,- 1.. < .: ___ . ~-· '. ·: .. ~-~; ;, ~(-~ <• t !.- .... . · .,,· .'1 ~ ·' .• .. ·.. t· .. I ~ : ,. ;·.' ...... < •• .. ~ . :, ' '· f ; -~ ·... · ; ' •' .. '·' .. ' ··. I i ~ i . ' ·r -38- ·• • I ,. . >; ' : ~: ' ''l ·. t·· '. ~ ·'. DR. BREWER: Yes. For B as for c they are ve.ry close together. 2 2 (•/· .~. ~- ·... ~ ' . ·Figure 13 shows the exjlected molecular .orbitals and ,the corresponding.· .. ' J ., ~ ~. states. For molecules with internuclear distances. in the range corres- . r -: i . ' '< '.. 2 2. l· ..... : ... ·.::pending to B2 ·and c2 ; the available data indicate that the y{J w '. ·. . . 2' '·.: · ~configuration lies low enough below the ya... :xcnnr:-- .:~... ·~· .~ configutation to · ., t, ~ ma.k~ the ~I:~·, state the ground state.· The separation will not be large · · 'and :for' heavier molecules, there is a good chance of: the. -~lt' state lying" · .. ; 3 · ; below the .3I:- state tor. the r same: reasons that were advanced :f~r a :1! "•\-' ·., . ground state for the heavier alkaline earths. However, :for all of these.· '. . ·.' :molecules, 3I:-, 31c, and::.l.E+ will l.ie. close together ~d all will contri- ,bute significantly to high temperature thermodynamic. functions. Figure:.: . .'' ' ,.,· 14 shows molecular orbitals.of seven electron molecules for comparison .1 . • } ,. I ~ , 'with Figs. 12 and 13. . ; ·;·., ~ ~ ' . . '. DR'. .. ROCHOW:J- Yes. · Will you please come up·. to t~e microphone and ·.. · :state your name.? -~ ~ : l· i DR. BOUDREAUX-:· Boudreaux, Louisiana State University, New Orleans. }. ·. With respect to the vibrational. spectrum of s , :has any thought b~en 1 2 I ·', .: ;.. ·; i.' given to the\~.possibility of asynnnetcy arising from the involvement 'of d perhaps hybrids . involving d orbitals as well? · ...... ·, ·,. DR. BREWER: '• I don't think· this trans it ion would take . place ·if the . mOlecule we~e out free in space o:t' in a synnnetrical environment . even I .' . . . ' . fLi' the d orb~tal were brought in. That . is J you have 'to have some external asymmetry, I am: sure·, in order to break down the sele.ction rule. .. ' . Now, ; as. to the way in. which the, asynnnetry manif~sts _itself 1 one _point . .. I didn't ~ring out is that there is a considerable ~shift in th~ vibrational ' ,.. :'H . . · ·. ··. · .• : -: . . ·.. · :: > . .·· · , , ·· i . . . ! :· :.; d frequency observed in the· matrix· .compared to tha.t:: for the. gas. ; Now 1 that ·,·._·,i.,;;:([ij :,' ... _:.. •' .....· ,, ... ·.. _,. ·.. ··~ ~J·.,_·l. .-_' ;·~ . . 1 :~ ;_ . ·t ·;:.. ·. ; .. '. .. ~- i .... :·,• . ;_':: f: ·!.: . .: l ' • • ' ' ,, )'~ \' ; ' . ;., :: ·"· ,; ~ . ·'j .·• .t ·: :' '· i !'' . ·e·. EfG :! 'i ·., ., ' ·. ·•'.'' \' •, . ! p i· ·_:;. -;:. ,•·. I,' '·I t, ,. ' ~ - \. {' . -; ~: ;. j' -'\- J; ,, ,, ,•\• ., ", .. ~: ~ -_1, ·,'17'-J.'n~ ~:r· "" · 1 "" : } ,, -.-~\A, ~-.:.-..::>-.• -· ' ,. '· ·, ... :.. ~.:'. .i :·· ' .· ·' . . . . •· . r ~ . ,,·· . .-:. i ' ----~--~~------·------~---~------''I i, ·., .. ~' :. i· ; . '-·' - .. ·,· ., ; ·-·· 2 ' . ',• .i: yc ;,c'! .1~'1r. \• .. '~ . 2 '2 : .l.f.' 1.,..-;./ .f ·i . ~rcr \'liT "·' : . ':-'-) '~ .1, . ~ i· \ ;,- ' . '' '--~. ; -~ . ! '"·- .,' ' -;,· . -· ~ !·. ~£ ' • ._f. ''i -~. . : ·: : :;_.' - ,·.· ' l. .... ' .• ,t.,. .,_, ·. ·>' ·., •'· . ,•. .. ·, ~- J' ,.. ',I . -~ .,J ·," ~ ._., ,. .. ·; ·. ·' . ·, :.\. •·. t; i j '. -_..,. ·' . ·' . ;.:. ' •, 1. ~ .j ,. .-! ~ i . ~. .. \·... : .· ·, :·, ,I -::-· ·(' _..__ ·, ·' ~ .'I ·.; ) .. ,· i ~- . . :! :;:{.i ,,· .,. ,,'.t ', ·,1 ··r ., ' ,. 1 ·-] ·'· '. l· ·.J '· ··' ,, ·; •' . ; ~ I . ~ ·· .. w38b- II .. / .·,J ·''·. .•.. .. .--....~------..-:..------.....;----~-- ·.; ' 2 2 '. :Ya i:U "':.·rri .. ., ' . . 2 . 2 :2:,- )jO' XO' \'fiT 1.. c;.ti 3',. ·, ·.' ··v- ~- '" U. ,-;II . . .. ,._;· I· .. i• ·... ; ,. ____ ..,. ... ______. - . . . . '' '1,. _:: .,·. .. < ~- ••• . ~ . . ; . '• :. :. '' ··H ·.; .. . ,.,., •.. · ·' . : ,: ''' .,'· j ; i.j. ·t.,, ' .. . . , i 'I :-; _2 .. '. '·· ·! ,{. \ ,) : ~ ··:- : . 'i' ·". \, '• ... .. · ;.,J- 'j :..... · '..,'i •I,. ·; { f' -.~. ... .~-- ;:: • ,.':!: ·'.: " ·' 1 -~ . ~- ·; .;- >· '',\ ': ' ·' ___ ,,,..,...... -~ ...... , ~ ... - .. ~:-;:.:::•_!;.. -:-• .· ·-;-·-·-····;-:;;:-·~·-;;.-;._------.-. -.;-;-:---. -.-. ~-. -_ ( . ~ ·. ' -39- . ' ~ . .. ·~;~~>~t ··~. · . ~_;would seem to ··indicate that there is some mixiilg of states or some other ! :· . . i ~ ~ ::. ;: : . .- '· ' . .. . _-: . , ~: · ·_perturbati9n coming in. : But the pr~ cause of the strength of the l5·:t~~--~-~;· •:·.: . . '. . ~ .. '• :J_ ; ;>;;:\,~ransition lnllst, be :some a~-~~ry u;_·; its enviroiUD.ent/·or .it ju~t wouldn't _.... .:r I ·. ·. :; : ; .. ··· ~: . ; ~- '.:· \· ) . .: . ·· '' .. .. J.;' 'f'!be seen. '· •.. _: >: ·· -·;- ,, ... ,i ·.¥ ~:;;(_ ·''1 ·:~ ·-1- ·-~~- . -'! · ' '' DR. ROCHOW: ·.·Yes· ·· ~ -~- ; . J< !... _! '-'· . . ' . ' . ~ · DR. MARGRAVE:' John Margrave, University of Wis'consi!l. . -· ;· • ... , _ . Leo, I w~s wondering--there are two things, possibly, in the structural :' .. ,. :;i.' ··-: . :. ~ . ~ ; ,'' area that you didn't emphasize. - One was the possibility of' high tempera- . ~: ,\ ' ; 0 ~' • , I • • ' ', ;· ' • ' : . ;: ~: ;ture Raman spectroscopy which Paul Bender at· Wisconsin has recently been ~ ~ ••.: ; ·:: i • ,, ' • .. t ·. ... ~ ~' £;\ £ ' . ' :'doing on_gaseous 'systems at siX and ei'ght hundre~ degrees. which gives ~ome i .J . . . . ·' ' ,;of these low energy vibrational frequencies, and- the .other is simply tR .. .~ :, I• • ~ o '! . /. ., . .. · ': work done 'with a better mass spectrometer than has previo-qsly been avail- : ~ . ; ' ~ L ; I • {I I :able. · : , _·· [ . ~ ; i ·, ) ~ t . \- '. '· .And then with regard to ·ground states, I wonder what you thought about ~- ; . monoenergetic.electroncombination with mass spectrometry for these· .; :: :~ :p.igh temperature species? • . ' ~ .. • ,. I ·, . .And~ finally,. it.· seemed to me that you perhaps minimized what might· : i' '.' I • be the m6st practical way to get_ these and that is j~st very accurate ,, ':.·., j ;:. '"' . . ·, · . 'determination of the free energies ·.·an.a.· heat::r·w-· 'g:tve--·a.a-"the- "entrop~ei.by ' ~ . ~- ·-----· ~---~-----·-·· - .. ···-·------~··.- ··-···----· ··- .., .. J.! ; • '. •' '. .. ; -· ' ~, :)s-_imple relationships; and then a pla~sibility argument regarding the ' ; •'" ; ": ) . . . -· . :• ' . , i ~:.;, ;.. structure might well be the easiest way until these very complicated optical .. i . :. ; { ~:- :.:·-L~·;;;. j· . - ~- .. :, . . . ; . i>:, \ . . ~ • 1 ! . j ' -~ ~ . ' • l . : . . ' i }) i DR' B~WER: ' W~ll, we t~i/ to: do just that til a ;number of: paper~ .. j ; _; ·. ;. : i~ and most recently .in a pape}€9 in .Chemical Reviews,_ iri which we have ·' ; !.. _,·) ... :\1; . . ',, . . . ·. ! . . .-~ . i :'·:: ~yzed 'all ;the :data: for- the _gaseous'meta.l dihalides,: and we found it :l-· :-. .• l ~ l ' . . . . -: ~ . . ' ...... ,': i . :. . I '•' ; )1ard to workbackWB.I"ds as you are suggesting .. rn th~. 'first place, the ex- . ; ;~-':: l -~- :' t ·,, • ••• ; ·; ' i •: : perimentSJ.· data one obtains from high: temperatUre equ,1librium measurements ' ~ I .. . • . ' • . t. •, , . :.~.\ ;;_:_-~:_.1~ ~-( ~.. l.~ :~:·;·... .., ·. ;t.{-, "' ~ :;;· ~-- ~·-.: l:· ~ '. . ' ' I •• ;·., >l :.'. . . ;_!; _!'': . >~ {'-.· .:-· .-, ~- .. ~·-, I . ' .. : . ~ .. ., i. . ,. ' ,'' :, ~ < I : • ' ': ' ~' ';,'! I . - • 1 .: .. ·; '' ~ 1·. ·._ ,· ·-40- .. , ·) '. ., ': '1 • '• i ,'I .. ,i'.' ·' • f , . always have considerable. error 1ri. them •. It is very d~ficult to e1iminate . . . ' ~ q f I ;> .1·;,. temperature dependent errors which will therefore show up. as an error in l: . : : ~-' • . . ,\·;· . ~ . ~ . . :·t ~ .. ;. .. ·· .. i . ' , ,·,:the experimental· entloo:py. ·.. • f <.·'.'I :'·I. ··~' Secondly:, ii; trying to. go from entropy to structure there are too . i • . :, . ; , many V~iables. . For. example 1 let us consider the s inl:pler case of the ,·:, .... ' ~ . ~ . : ; ' '. : t . i . . . . ' ' . . . : '· l:: l1:a.lkaline earth dihiuides let alon~ the transition metal diluilides where ' ~·. 1 ' ~ ~ . ) ~ . ) : ~ ', . . j ,·. rwe have the problem .of .. the electronic contribution to the :partition function. .. • i. :'." We had to.estimate; because of the lack of-spectral data, the inter- nuclear distances as well as the stretching and the bending frequencies. . ' I . :• '· ~ ·:'And if we ·had more bond angle data like Klemperer's mi,ght '. -~ - recen~ dat~e I ...... I · ·have tried to estimate the bond angles . Although, in_ fact 1 even if we had . . . some bond angle data, we :probably would not want to use the estimation of , .. ' '. ' ~. :.additional angles. as a :parameter. The data are not good enough to stand...... ,, ..... r' ·-'·-- .~. ; •• J. : ;· 1 :: '. that' many parameters. ·Essenti~lly what.we did do was.t6 take the experi- ';: . 1 : . ~ ·-.~ i . :· .. , :~mental data, ma.k~ guesses of internuclear dist~ces which can be done :: !- ·..• ;·' .··.:- :·:·.:'without too much error, and obtain empirically th~ bending frequency, which -.- '·' . -1 . .( ;·: ~~ .i. ··.;. '' :; :, : . • ·- ::· ·:is .the parameter which has the greatest effect upon the thermodynamic r·• ~ ,. . But it would not be possible to fix both the bending frequency and . : ' ' . . -~•• '.·.. 1,_ angle from the experimental data; so that we really have no alternative . .~ ·. -. : . . ~ '. .'; ~ .-?~t to throw everything, including the effect of ·vapor imperfections or ;. ;· ~- ~ .. ;.~: .'-r i ,' · :' ., I , : . . !< ,1 :; gaseous :polymers, into the bending fJ;"eq,uency as a :parameter. There were 1·',1' ··.;.. . . ' . ' '! ', ) ; (}-l j;st too many things that -wo~ have to b~ fixed to hope to :pin down the , ... ·;.~tructure by going backwards from th~~ thermodynamic ·:Properties.· Although· ·;.,(., ' . ;,;., )~ can be done as it was in the case of the cuprous chloride where we were· : ~-: . ~ble to guess the. structure on the basis 'o:r. the .. entropy,/ I think normally ~ . .: •... ·.:: j • ,· ·'·. • ' • ' • • ~ ~- . . . ' -;< . ' : ~ ·. ~ .· . ' i; ·" . ~-- ; i-' ~.: :' ..' · ~ :; :, it would be rather 'difficult to do so~ -'~ . ,. : ~ . '\ •. r . .' . '' I' ~ -. ' ' . .; ~ . ~ . ~- . 1 ~ · ~ I . ! ,, .· .. "'- .. · ·'· '· .. -41- :·_, ·- . ··~: ·.' )· ! j; i' I,' . .·.Those ot!i~; inethOds you suggOstOd vciuld ce~a~ be :.important~ . ' :;,};;:·~~· fact,'.the'~vent o;f ia.sers will ~e the Rama.i:l' 'meihod much mere· '\ .· ,·· . ' . ' . . ' . . ; :' . ·_ i: . > ~-' '. !" .... . ·.i ;~ractical for. gases because such high intensities· mayfinake it po~sible i. ;;l f:·. see Raman··\spectra /in gases _eyen at high temperatures. •Infrared o ::'I' . . ' . ~ .... : ·, . ; ?. . . ~ ' . . .. ': .' . : . :. . . . • . . : . . . :. . ) ··_;"• i ;.. :. ' ::0:; :s;r>ec~ros copy. 'Will certainly be. of ve~ .great :lmportan<7e not only from . · ." ·. i' •. -~---L ;:.~~:~~~-~-\ --:~- ~_ ~ .i· .· . ·-: .- ··:. :- .. _._.. ' --- .. · ---.. ·.:-- : . . ·i · . •'. -. ·' ·:::: .. :';the· pOint of vi~w of getting inl:"ormation ·from the yibratiori rotation . ·_; --~.- ~\L_· . ! - - ·. , ·-~ ··.; .correlated with electron orbitals that ma.D.y. of. the ··low-lying states ' ': . • . :. ' ' • • • I • , ; • that are missing .would be seen ·only if someone looked for ·:!ihem .in the. . . ., l ,, • .. ·.. •.- ... .; .·. i-'ini'rared. .~ No one .has' bothered. to look• ·'so it is quite clear why theQe :. ~ . •, . : ~ ;·... ' ' ...... , ·. . . . ~ ,. . ' .. . >. ·. low-lying' states· .. are ;:<· ·~ missing. · It. will requiTe spe'ctrai stu~ies ·over · L.i·. · · · · · I T ; / ;_ , J.·,,~ · _.. · ~- · ' ··._ . '. · · ·-~ ·. · · r--····-•~-;.~ ···-·-'"'··-·"-··--······· .·· : :the entire spectral· range;· including . ultimately inicrowave as weu-a:s.. ---:: . ; 1 1 •. l .·. ;: '·;·~---~; _;..;_ ~--~ .. -·- ~-' ~.-.:.:...... ::. ·"-~ ....· ~::~_,).._· __ : ____ -~--- ~--~- ----.-- ~-~--··· ·__ ~··-. ·-· ~-~- --~·--·--··-··-'--"- -::-----~------~:-- --~- _::· . ~··~ :· ~:·--~ ·.·~-;-:-:·· .---:-- ·-·- .. ·---.. ·--~--~------.... -1 ' ~y~_quwu._:~.utraViole~.:: spe~.tra.. o;f'. h:igl:l. __ ~mp~ra tJlre. __ syatems ~ : , . . :;.-·· ,. f -?: DR. ·RoCH0'\:'1: Professor Eyrizlg? ·· ·I .... i ... DR. EYRING: That, way, of course,. that one thinks:.of is ~he mass speC-:). .,\ .. ';' trograph .and getting the concentration changes with t~mpera~ures and . ;' ~ ' . '. ' -~ _. • "l ' ~~ \ • '. : ·pressures and so on1 and one will at least either get· equilibrium values ...... _1-. l ' : . 1/ . 1 < (,·,:. ~ ' , 1 ,:(~;:::and the~ get' heats and entropies or else one would' gei;: rates of ,reaction • .:, i .. l ' ; ' • '·· i. . I' i • . .. ' . .· i .· ' ; \ ·: i. ·:~That . is 1 this couid ·be. done .· dver a range of values • .· ;: i . . . '.!, • Is there .anything you want to s.ay about how ~ch: has been d.one or ·.. ,. .:t:. • , ' ' '.; ~' : . • .. ·• . ' . " .. ' • . ~ . ·, tf . . . ' • .·.: J•,:ca.n be do.ne with using a. mass spectr.ogr-aph :to' look at the. populations of . : . .. : ... : • ' f • ' ; ' •• '· :, : • • • : • ~ • • • ' • .: ~ ·:~ • • : ' ... • • • ;:\ ' : l : ' ! . ~:; :. : tl?-e a: i:f'feri.mt' kinds :of molecules ? .i :; ; f . ' ! •: • i • • • · ' I • • • ~ ( • ") " t . . . ' . "l ' ;. ::~ .~ ' -~ ,. ' . ·,,r . ;. ,'~ . ! . ; .• ·. j ..'· :i· .... i·' . ",'., •, <~ ;:::' .. . . ·i .;::.' ... ':' .· ~· ·; ~ ~. : . ,, . .. t-···,.' . . :··i ·:.···,· ··· .. , i' 'I'' ,. .·.:. I ' ·. ~ i C 1 'I '-42- ·I r •. ' ' ! · : ;;;t'j:; DR. BREWER: A large bulk of the molecules .that have· been discovered .. ·J • • i ·: Erecemtly have ,bee~ discovered .t~ousb. :mS.ss ~pectr~~teW.xam~ation o:r. . . . !:. ~ $ ~ •• ' • ,:_: _: ! ' • . : ;. .. .. ! .: :: .. . . ~ ~- : , ·'d -~ .. ~ ·:the ions produced on bombardment of molecular beams :_by electrons • ', . ' •. ·.\ ·.~{ ~ .. ~ .. ;_ ,. .. : . ~ t However, as with 8J.1 high temperature ineas\l.rements and particularly ' ~: : ' ' . . . :, .; ·--~: . : ;' i I . • ' • • ' .' : . ·. '-;,so for t,he mass spectrometer measurements, there are serious temperature .. ,::;1' ·"t • •j;_-,! i . ; ; :::·;:dependent· errors·; so that in practice a large proportion iof the entropies i ' .'!'.1 .: ' . ,. . ' '; ~ 'l 01 • .!' i • ' ' • ' I '• ' • • ~ 0 ·. -; ; . : ;: obtained from mass' spectrometer study have not been very accurate. In ·!, .; : '; .. :'\.general, I. would. say' the present status 1s that 'the mass :spectrometer :.1- . '·: ..· ·r:t · ·:; 1 .. is unexcelled for showing· the presence of these :various species, but r' ·:; ' ' . . '•; ~ l :·:-. :·,:\would say that, in 'general, other methods are preferaqle to fix the ·. ', . ' . :·entropy of the predominant species . after the mass spectrometer has identi- . ~ :· ~' ; -~ . . . ' . . ' . ' . . ' . ! .. . ( ~ : . ; ~; ··~·fied the significant species and has determined the conditions under which '• ' ~ ' . ·': . ;: i one species is predominant. / .,_ DR. EYRJNG: Could I just aSk another thing? ~: t,h:i.:D.k you ~can hear ' ' -~) ' .... : :~;me from here. . :' ~ ' ; :. ' ' ' 1 • l . • 1,f'( ··l;·l, ··l, ..'; .. •'!. : These kinds of species 1 are we. going to get big· activation energies. l . ~ . ; . f ; .i 1. .. • . i ; : i ~ . . . " ' • ''!;'for them?· Is. there enough know to ~oW: how fast we get relaxation time .·.·,. , . .. '•:; ;. : 4 ' ~ ::. t -~ ~ ~'; ; : _f I ," .' • ' • • •• .. t • • t ; • , , ',,,·;,! anO. what kind of activation energies we ·get? .. ; ' ':~ ... ;J!! ·.. ·.. I su~pec: ·theywould be low 1 in general. But. I;:~~ndcir-~ BREWliR: .•. .r'i!i; ... . DR~ Well, it varie~; that iS, I. p~es~, you,1mean activation · ·. .: .·•• ,:. \:·.: __1 .. ·.:.•_ .•.• ,..:.:... :_:. 1_:.!: :_: ..... · DR.· ~~J:NG: ~ That, arid I was thjnking even if )'OU ~ pressure-~ • •· . : , , ' ; · . , .. DR.,; BRE~R:·::.Yes, Kan~:-and I; s~owed in a pape~;:>~ome years ago in ··· 1 , ' , , 'I' . , , ._,: .. ~:; -~: .: L_: p·; ; i i }:our study.. of. ·ara'e1lic and· r_ed phosph~~ous, for which ~fe P4 and ·As 4 v~pqr~ .:-: ~-: ~ i i ,• . . ' ',...... : ' . . . . : .. . . . ' . " . . ' ' . !. ; .J:\:iidng species · a;re complex molecniles with.• stl0lctures considerably 4 ifferent :-.. : ·:· 'f•:;\!! ' ' : ;\ ·.' ·. '/' ~ i I •• . i ' : • . · ...• : ...··' .•.· i : • ; • '.; ... : . .· ...· • .. • ':._,,·i::fro:m that •in the solid phase, _that· there were .enormous ·vaporization· ;···I.·,::J~arriers;~ ::rn fact, ~h~;ac~i~ation :·~~er~ w~·m.anY-.t~~s the equUibri~·· ?>--_; f ~-r-~- ·. ·. --~:·.. ,. . . -,·. ~ .-...... ;- .. . :- ~-~- ;.. ! ·: .. >; :~;; ~·.. ;;: t . ' ; i . ! • } 'dJ \ . : ·...... \. '; ~ ·_ ;~ ' 'I: ' . ·;.~ ; . .. _5.', . . ~ ~~ . . .r ·- . r. . . . ; ~ ; .- .. ···------,f.' :_ . ~ :: . ~ ~ : . ·:. ,· . ' ' . .;- ..., . ·~ .. ·. f ' .•.; ;_ ':<;- ~43.:. • ; ' ; i. ·. ;: ( ' i ,~ ~ • ·, . ~ ~ :~ ;::f~·; ~ I '• • !: ·~ ,· ·.·· ~· .··i :U ' ;. ! i ,<;gf sublimati~n ~ ': It. appears to be'' a. gen~:ra.l 'p:rincipl~' that wr.eneve:r' the .~t ···<.,:-;;j;i.: ' \ _.,, . <'; .; f .. ·. '; ·:··s't:ructu:re ~f the' gaseous molecule,' is con~ide:rabl.y different .from the ' .:: l'l '··! ::> \;: : . " ' .. f i . .. 'k \ ~ . .i ~; : 's:t:ructure in the condens'ed phase 1 : one should expect quite cons ide:rable ' . ·.. ,,;.~_·<· : '\ " ' J'l'i'~::_::~- ~~l-:_;·:;; ~- 'f ·. ~ ··_ ..•. -'t'·~ :~q: { > !.';: :~:~~tivation, ,energies .for their p:roduc~_ion and. th~:refo;e_ th~t. they would 1 ~ :{ , f :: r_;: ,~:~ot appear -~n free• ~apor:l.zat.ion 1 o:r w~uJ.d .be g:r~atly :~eclu~~d. But as one ~ . . . ; .. '. :; a.P.owed :for· establishment. of equilibrium, kinetic measurements will often ·.-_ ',' >. ; 4 i.• ·: ; -~Tss them. .One of the most inte:re~ting examples ·o:r fu~ibited vaporization ;' ::,' that we have studied at Berkeley is M~tz:f~ld~'~ wo:r~/:n .liquid sod:!um; . :. ., . .·1 .!- %~ : t. ' . ;-:. : · c'~bonate. '.The k~etic barrier arise~ even in a liquid system because .. ; ·:• . ' ,: I . ·. J ·j ': .the carbon~t~: ion1 .wh:!.ch has a t:rian~lar s~ructu:re :~. i;he;:melt ". de~ •. ,:1 t I '·d ' • ; .; : ;;; '. c:Q,m:Po~es' to ,a:'liriear Co2 ~ Because: of 'that d:rasti~ ·change ;m· str;uctu:re" r ·' ~ ~--~ ~-.:;; . ~-~ .··. '.;. ~ ·, . . ' ..· ·. .· . ; . r ·~' ·~ • : '.' .. ;·q a •large activ~tion energy- :resulted. :fact,.•he was unable to get equi- 0 :(,n ;" • J ', '.• · : : :,': :.,: I •• ~ : • • •'' , / ' ' •• • • ~ , . ~ : ' ' j· ~ib:rium :results; from his measurements, because: of the' vecy large act iva~ ; ' ,, ' t . ·' . • ~. .. 't ~· :' ! .. . ··! \ ·· .. In the case .of ,our :red phosphorus :results J the' activation energy is. •: ; '. sq: great that if',some.:red phospho~s crystals 'lvere sealed. u:p in a conto$-iJ:le:r,. ,: . \ ~ . . ' . ' ~ . ' ' . :i:'. 1 f'l . '·: i ~ :i:t would take the order of seconds to build;u:p 'to' anywhere near the e~uio.. • ~. ~ ~- : i. 1, . : .•' ',• • . . . . . ' ...... ·...... ' • ·} : . ' :•.' .. ·:-· ',• .. r ;lib:rium pressure.·.< In :fact, we concluded that even a. completely sealed . cell to. :Prevent :o:r ; the';. <';:·~~dsen wo~d. riot:·~e ~ight,· eno~sh; :lo~s·. 4 th:r~ugh ~' -;· ·, L i : , ' ~ ·.··. · .~~ .l. : ·. , ·. ; :i walls and ·allow' establishment of ·the .equilib:r~um :p:r~ssu:re with respect :··,"! l ': :::· . ~ : 'f.. ' .... c ~ ·:, .. .; ...... ·.• '.• ,. ··: '. '·· ·:· .; -~ . . . -44_. . ~ . !; . . { We also showed in that work that it is possible, however,· to add .. ··: ~ ' . < ! ~~ i .J catalysts to c~talyze the vaporization to get around· these barriers • ..· t ·: . . . : > . ~ ) ' ' . :,. j li . -~ ' >, l . :.And we did find some metallic catalysts that did tre~endously catalyze -~ ..... ;: 1 J ~ l ' • • • • :. ,., • ' . ' • :-: ; . ~- ; .. . . . ' ' -~~ . '. •.··.· ·:f., .\.. .· ; .. ; · \<:the rate:.. of' vaporization. · Ther~ will surely be very substantial activa- · .• ''- ~ . :. ~. : . . ' . t ~ ~ 1 ' ' :; ; _; tion .energies f'or some of' the very complex species w~th drastically -~- ' ; • 1 r •.• 1~ ; ; :Ci;dif'ferent structures than those of the solid and f'or. that. reaso~ they .. ; .. 1; .-. ·'; .. :Will many times be overlooked in casual· examinations B.nd will require · . ' . '. : • • :; ~ • 1 . ' The other way· in ~hich the mass spectrometer wi~l clearly be very .... . i ·' ~ t I ' . • ;.. ><.:·.:useful is 'as a purely analyticai tool. For example, ·there are a number ; ·~ ) . ··. ·, 1 1 · · :··.of things that one might do to a beam of' molecules. One might subject ; ~ . ~- . ·-- :;it to electric t'ield~ 1 magnetic fields 1 or any other sort ,of interaction, \ • j . ,, ·:· t l' ,_ · · .·. ·: and use the mass spectrometer as a detector to find- out whether or not ·• ~! . i l '' 'the molecule responded. to these probles.. In that way· one can gain addi~ .:_\". · . ~ · '\ional information about the structure of the molecul~s. .In the past · r·.~~~st of the moleculaX beam work has be~~ ~estricted' to alkali. and alkaline. ·. ·.: t: I,: . ··' . . e.arth metals because they ionize so r.ead~ly on tungsten filaments and can ~ ·.;. : . . : ~ · ·. ;: . .. ~.·be easily detected . But _that limits one very severely and: I think in ·. . ·-~ . '• . . ; . .: : ; ~ ~ . ] ...... . t. j :~~jnore general studies an important use of the mass spe~trometerwill be . . .. ~-: ; .'< ". ~ u.. : . . ! ~ f \.·.>as· an· analYtical tool to t.ell ,whether' or.'not a pa.rtic~lar :perturbation \.:·;,r';_;;:;~, ·.. · .... ·. '·.· . ; . ·--~ ··~ ·,·: ---~~: "":· .. ~ .. ' .. ·. "has' any effect upon deflecting a molecule in a molecular beam. : i·· . . f • • •• ·; :· .. DR• ROCHow(; Thank. you, Dr. ·i ' .·; .·.: ·' .; .. . 1 Br~wer·. ('' .. .. ·. ... ~·~ .. ' t .1· . .· .. l •\' . ' : -~ . ·' . r :_ ,~. ..~.: Dr •. Burg?:: .-:. ~--; ' DR. BURG; ·(University of Southern California~ Los Angeles; Calif.) ·• ~) ; } • : • . ·, . ' • :' • • • ~ ·.• • • •. ' . . :· • >. ·.: : i :. I, was just wondering what are some of the simple~ aspects ?f the techniques • ",1 . ;·_.-. : .:-· . \. : :;·.:' .·.' •, : >.tby which one make~ these observations? ,. ·· , ; :\ i · · ,~·:- . .',·, .:•1 . . ' . ·.' . >;; .Jll· ;,· .. ~:;: .. . .,;· ; .. .~ ' :;. ~ r . -~-; ·J l,.~ ; ~: , ,_._ . ,· .• ,~ ~ '!.' .: .! . " .. : ' . -: ~ . ··-.(I·; . . • . t: ~ ' , . . ,, ; .. ~. :, ·• ,. .• ..... ~ ' .. ,· ,; ' ·, ·. ; i . •~ f • ·. ... •. . ,. . ' :-4. 5.- I· l• ~ i DR. BBEWER: Which ones? : t ' •$; ' ~ . :. . ' J ' ;;:~ ;~t ; (~ L;;:exa.mple:, ·for .the spectra.o-£ C~ or CN, which we are ~rently s'tudy1ng1 in ·•) · · · · ~ .·: :.·_.wfact have been Cu,rrently studyin~~or almost ~enty:years (laughter), : ~- .·:-. ' •' r • ~; ~ ~ : ' • >, '· - t •l 1 ·.- :',' ~ ·: ·y:we use a graphite·.resistor whi,ch is ·hollow. We pass' about 2 000 amperes _; 1 .; \ ·;! . l .. )~ ·~T jthr~ugh; this graphite tube which has a 3/4 to l inch: d~eter} For c we 2 .\' ·... ·'-· . ; i •. ~ , ; f..~: !don •t have t~ add anything' in 'th~ :t~be ~cept some ~gon~ It is necessary :·, q;: ...... ·. . .. ·...... ~ . . ' ,i · · :. •to .add argon .becaUse· at these temperatures-...we. norm8.lly work .between· two ~ ·: ; , }!. ~ . .· :, . ' . ~·. :· ~ ,; . ' . . : . ' . . .: . ~ . . ti 1and three thousand degrees Kelvin..:-there is a substa:zitial equilibrium par- . ' 1 . . :; . ~ ~ .i! 1 . . .~ . . ~ tial pressure of electrons. We have about a 6-volt drop across our resistor ! ;·.·:·r. . .. ·.. l ... ;·.!; ...... : . ·.···. i- ·: . : ', ·and if we had a very low pressure 1 ·the electrons .in .'this tube would be· ·, : ~ -·. ~: .t j i ·.. .~- ! • •• . ; '" • • . ',_!· .: : ; ~ ;;Y :accelerated by the 6-volt drop Bl;ld ~ould bombard the ·c molecules. · We . ... : ' 2 :; .. : . . :' : ' would not have thermal equilibrium, and we are ~teres ted 1 in this case 1 > .' ; .: ;l ~:;!:; . '' -~ ; :: • 1 . ;• ... 1' : -i· . .' ~ t ' ' { ! i ··; : 1:in having an equilibrium situation~ ; So we must add enough argon to decrease 1 ; i; .. r. ~': ;! ! . ·: . ' ( ·: ; . •. . . . • . . .• . ;1:,;;:the mean free pa:th of, elect~ons so. that they do not move long in any one - . ~ . : . ' . . . ' . . ! ' ~ ··'-/!.\~irection and therefore do· not pick up energy from the. electric field.·· .• ' ,. : f . \ '·; t ·• 'I' ' .--·~' .. :L ... _____ .. c. •.. JU.. ------~- ----· ... Jl· r: :: ~ ::·j.; .•. AS.:ide from the argon,. a .study ~f c2 would not r~quire any other mate~ .· :·~·";.::::···j.-:1<~::' .. ·. ·,··. '•·.· .· .. >··.··. ': . . . '.. .· . .· t. ; j .. '··; i;l;rial insicie this tube which is designed. to give a.. uniform temperature region. '' ~,:; i'· ,',(j!iif~ meas~e the t~eratuXe ,;~~fY monitoring the.ga~~ous emission'·· , , '', ::.: ~ r ;/ )tl!fit~. a ph~toele~~ric:. pyrometer .... Ess~ntially I we ju~T le{: a photomultiplier.. r . i: \ >) i look at the ga.~eOUS emis~ion 'and this CSn detect e:x;tremely small changes . .; ...~ . i Ji . ' \ ' ' ~:·:·.:· . .; ; . '· ' . . •: ') }. , in the temperature' becaUse the. emiss,ion ·. has.. ;an ext;-~~eJ.y::high temperature: ·····_:(:.·.·,~.: } .. < ·., \ ... , / .~ .. ~.·.~: :_;_ .. ·f.J·/.:: .:_;_: <·.·.~ .. r.. ::.;:;;t\. }. : :) j 'j j: , . ,--~~ ~· ' :, '~ :~ ' .' I . ;~.~-· ;~ .~.• ~.;·;. J l-_:· '.L -~\-~· ···: -~.-._, ... --..._.. :::r~·.:···. __ f. ---~--- ;·;.~ .q . ; ~ . .-.~ ---~- ' ~ I ., . , • ' . ·; .. : ., ' t .\' •. ~·,I ; ' ?i '; '!:. . :.::~ !'i ., ..... ·,-_, .,· ;._ ' . ; :.. ·,''>I '·; , ...... -,··· . \· . ·• t .: .1 ... ·'! ; , I ' { .· : . • i:; . ~.; '} ' " l . • .·~ ~ • • j . ;.: : ' • ~ :! .. i' ~.-: ~•. ; !: : ~ . -~ '...... •: .. . i . 1· { • -~ . ~ :·: . . i . i ' : ;;; _: ~ . .~ ; ~ : ·. . '·! .···:., ,:~ . , :·:,};·:":P~oefficie~t/ So·with this photom-\lltiplier det~ctor wd cah VarY our cilrrent ·~ i ;: ::.. f.~;· •j · ·•. ::{ ;·;~·(l~llr~ugh o~ re~istbr~to ~intain ~a·:·v~ry' ,constant ~~m;e;ra~~e ~ i . ~· ... ;• ~- ··.',. t .. .• ~ ..;. :·. ;; : t: ! . ~ '\ . . \, : . .· . ,: ; ,· .!... • • • • • • .. • -. ···:: .·~~<~~;~ . ' . . --~- . ·' .. ~ i ·. · ;! :. ::.:;.·,.:,~.·~.··•.\.:.i.l.f.\.\ Th~s.· :;c,:.av.:i:y.:.· ·:t~ .e.~·ss.ential~y:·~.•.a~~~.·.a. te···.:d.w~:~ .·c,}an·"·~a.~: .. :w.e .w.: o.rk~ith it in· rr·'\ ' ;,;;n,f"o weys, ·, We e~ther ~ok 8;~ tlie ;emisSion spectrum a;i ""';~ous temperatUreS ·;•' j I .. I . ; ' . ·"'.·through the .end windows I we~ outs ide the hot' zone 1 or we;: pass ;a light. beam ·< ··.! ;, i f:i ~. ~.r~hrough the gas' arid observe th~ s~e-·spectra iri abso~tidp.·. If we are . lfte CN we· add a:·little ·nitrogen;t :generally . :: ·t·:: 1 !·r ill ;:;,i;~tudying someth~i 1 ~thoug.~ ~-~!; ~{~--~~~:: ': ·.: .· J; .. :; ., l: .! ,f )~hat is ;not necessary. ·There. is enough nitr~gen pre~Fnt to see CN quite ··.~ ;._-:;·!::. . ' . ··~. ' . l' . ' J . ;·: .. ; r-; ; :readily-; but.·, i:t' we want to control·.the amount o;f nitrogen; :we add a. little~ u;•l: ~ .•. IT ~e wsnt to s:ud~ so>Ueth~g l~e MgO ,: w~ic~ :+ ~v; studied~~~;;Yfu ;,j(~Y..8.ctly the same way -t1e 'lin~ the graphite 'i;li th :tarita.-?-Um carbide because.· - :.!. •. '. ___ .. _...... ----···· .. +--t~·-:·-·.· ..... ;• -~- .... -· ...... --··.-:. :·.~ .. -.. -- -.:: ·---~ .. - ·-": . ....: ... . - · .. - :·. . - . --. - . ·.--· -··- - ·--~-~- .- ... . ·.,'. :: ; ; ' r.;. <~-~~-:~.~?~;:~~~.~~.i~~,-~~--~~~tact·:\.~i'~? g~a~lii~ ~ .The --d~~}~ssion o:r; carton · " i . . .. f. l ' '. ~ . . ' I -' ;i: ·.' ;throUgh tantiU.um: carbide is' slow and ;this ·reduces the; carbon. activ.ity in ··} ,-=. • r :rL 1 . ~ . . , .. ~ . -. .. · \ i• :0::the inner zone. But t~talum carbide ca:i:mot:be iri contact with. MgO_, either; '{ _1 ~- .• J J wOl~e; the ~~tal.UJn carbide w~th tungsten; • ; Ti,n~s';~n I;eack only slowly . :+ '.' . J:,·ith MgO; so we>do.. ha:Ve ,~~region wh.ich is' not too 'stron~y reduGing :inJ,rhich : :. :~::. . . •. > ~~ . . ' .i ·' J.: .~ j;:- ~;'1v.~ can ma.irltain. Mg .. ·. .. .:.... :.;.·. . ·.: f..· : ..=,;, . . . l . ~ ~; ~ .~ :.~. ' ·:~ ··. -: ... ; ·....•. ··. ·: ' . . ' .. ' .. : .; : .· .: : > ' ··. . . t TL~i having ~·equilibrium: system b~t want,, to. generate a· spectrum, would be., 1>H~-~ j l ~· ; ' ' r · '~ · '. • < ~ · , ·. •· · . i .~to use. a ,hollow. ci3.thocle sourc.e, an arc·. source; "a.·mic;qwave. discharge, " : ; : i. i .. ' . . ' '· : . ·, :~.. '· '·• ~;-}: ~; \ . . ·:: . • . • . • : : ••.: . .. .' • " ; ' . . • .• ' •• . • ':, ~. 1 :' .•.•. . J ': - • : '• • 1 ~ . ·': . .. ' .•. .·.· 1':. J<_'r'';;;;; . . : ,: . ·.·· .. ' ...· ···.• ' . '·.; ' . J \ :';• ,.\ :y;ou. don't: even have to .do. it yourself'; you can jus~ go' 'out and iook at the ·• .:'•},~~; , .(·~ .:' ~.'';<_::~··. ~·1 ··.,' ._,';·~:>.:; ·{~ ,' ~ . . ,:· ~·~,· ::· .. • ·;~ . ·... Js'tars. The~.sta.rs :a.l'e;:~orider~l~ .so~ci~s o:r high .tempe;rature spe9tra.{ Tne .. >i r ,;~ij i . ., .; ·..... ··. .. .: ·. . ! . • : ·~.4 , , , . ;. \ ; .· · r·ti· ,; ' ' i: ~ . .. • • _;,_ •.. l'.'. ,~---~-~--,:-=~=~------=---~----,-~""'""---,.-..---=_,. I·'. ,_. -,!: . .. _ \ . ··:: ... : · .. ·: .. '· ~ ' ·. ' .. ···: ,. ·. ' .. - ' In working 'With molecular beams,' one will norma.J.ly have' some con_;· -~ ' .. '·' ' ~ : l .. ,...... ·. : .·· : "·I ·. . , · .. · ··: ·. . . . ' . , . .,, . . ~' :. ! . ·; j n ·tainer 1 a Kriud:sen. cell· made of' some material which is relatively non- i ; :··~ >l ;;: . . '. ! : -\., . ' .·' • ·.. '' ; ' ·: ' '~ . . . : ' . ;: ':.::reactive with ~he material to be':studied., ~lith a ~lit;· usuaiiy: a long, .t' ' '.. . ! . ~ .... . ' For our :p'iirpose~ a consider- :. r- . . ~ : :; ·_.;~ ~blec divei-_gence:_ c;'l__ th~ melecUiar beam is not. se::;:i~':l_s/ s~. :tha:~---~le do' net' use the ~ ~ . .. '. :i. '>: . . .. ·. r'· 'r classical molecular beam conditions .. We use·a very strongly divergent ·' . !. ) ' ·c , ;; ~ ; ~. ~ ' v . ·. . .1 ' . . •' f ... ~ • 1 . . . ;·,:Professor Deby~ suggested many years ago 3 .to get :a ;very high: modulation ·' <- -~--c· ·\ · ~-. i : ~ . f) ' .. l.' ;_,;;frequency. ·The pUrpose of' modulatilig is essentially' :to give us a time'. }. ;... ;~ ~ ii ' .· ~ .'<; ~ : . ; ' ,;measure. :._· : : /:·~:;. ,;\ ~~ ~'~ ·l,-":i' ::':;)~!· This:mod~lated light is passed,through our molecular: beams, is ab;_ ;' ' ~ :; ' \: ' ,...... ; . , :1 •:,s'?Orbed by.the,gas. and then reemitted. in fluorescence .. We. then examine. ,,·<·' "•l,; I • • • ' • ; • • • .' ~ ·.;. ·:-.·r ·;~-· n. ·: '.; ·- ~ ·: ~' :~;)the pha.Se of'< this f'luores~eiit light :and ;compare it ·t.~ our: exciting light l ; '~! l ; . .•: : ' .. ' ...... ' : ·. . : . ' . . ' ' i !,~ : . Ylf·r:;:~d in,.th~t way:~e~~sure.how long th~_molecule held 'tAis ~ight; before it·· ·.: ;!~i.~:~eemitted > And we· use "s.~i~ \~:c~~queWot.:thia 1~y-pe to pr~duce and ! ·.. : . • . .,.. , ! - ' ;, ·,-. ' ... ' ~- ~ '. •. ., •· i'~ I ~ " · '· ··;:study high t'emperature systems,.c · , · r ,. ; ~. ' ~~ :' f i. :·;: ~! ... DR.'< ROCHOW: : Thank you; Dr. :Brewer~. ''' . ~ ;. ' .: r: ' ., .. :! .. ' ~ ! . ·,,. -1 ~ j j. ·--48-, '\.·I .· i ·i.i,!.ll ;.. ~ . ~-. i. ·:... : :. ;' . ··· ·; .. ·.,.:m.ore and. mere ioniza.t_ion; and ho~ can you: t~ll that ;·your;a.ssignment of lo' .1 '; .: ~ ~ ·. .:: ·._ -~ .,. .;- ;.tH ; : . :...... ·• •' .. : ,. ~ ': Lthe ground ~tate is -'due 'te> a. neutral or an ionized ~le¢ule ~ ( .: '! ;t I :• ~ ., .:_-,; .. ~. :d!: ...... :. . ~ ·. : :·! '· ·:;: .iJllporta.nt one because as I pointed out .earlier, we have at· our tempera.- ". ~ ~ ~ ~ :"L:~ ! . '' .. . : ' . ' . ; ...... ' . ;. :) li :tures 'appreciable 'partial pressures. of electrons .iri; equilibrium with. our. ·! :-':"o.· _; ' · · : !.~ '{Psystem5 a.nd along with them IIlatlY' ion.'s ~ ' ·· . ; : ( ·; r· '' ' )' ' ;'!\; To giVO y~ ani p.ustration; a reW years ago 1<: ;were studYing the '< .;.:! . •. . . ·' . • ' ' ...... ', . . .· . . ,.. ' : '; ) . ;problem of. the very strong absorption feature which is seen in the ultra- · :. 1 · ·. ; , :. 'iiP; .· . ·•· ...... : . . .. ;: ; . . : ...... ,( ·. !. ::U:violet specti-unl of carbon· systems •.. Iri fact, i~ was ~irst seen in comets . .··:~;·:~,·t~-! ,' . '· .··. ~ ·.. · .. .· _:.. ~. .· . ·. . .. : ' .: ·.. ' .. - ~-'· .: :::·t: 'a.na. originally thought to be c~, but has been shoml: ·to be due to. c3. ' •' ,.. ' .. , Although carbon stars are very' hot they emit little ultrav.iolet light;, . '• ·! '. '.· .. . ·.. ··.. 6 . '·' ...... ·..... · ...... ··: ·-f 1'. ·. ._· r : ; : .. ' aria.: we foun~ spectrum in the. ·carbon· tube ~ce. which matched ·1. 0 ' ·. ' ~ .! : ' • • • , , •• 1 f, I • ' : .; ' ~ :- . ' :·j'· We wished. to ·,: \,.·. 'exactly the missing ultraviolet light of the carbon stars. ; ·.• r .. ~: :det~rmine ~the m6lecule that was :responsible for this" :vecy strong spectrum; · . '.. l :. ,, ,, and. we applied., essentially, the mass action law. ~itially we started. , · ~: ; >.f'~:·<~!. ;, ; IF ; ; ;' :. with just' gra.phit~ and. the whole chamber was saturated. wi:th respect to ,! . . . . graphite •. Thep. byti.sing tantalUili carbide barriers for the diffusion of / ·~ ''• i ;:: , ( : . . · I 1 '; . i• i!jcarbon we We"I:~ able to work·atlower and. lower carbon partial pressures. ; :; \i .· .. ; ; ; , ;): We could. see at. the same time s;pectra that. are known :to b~ due to c and ...· 2 •f I • '' ,· ' > ' : '' : ' ' •' ;J :%~e compared. the reduction of 'intensi~y· of the uriknown bands wii;h those l'::l :. ,'/ .' • . f,otind. .. they went. d. own· more rapidly a.s we · our' CSJ;"bon ·: . c2 ·we ~~duced . ..' 't ·. ; !l :_:o ' ' ' ~ ~ ' ~ -, . .~ - : .I, ; .... .-.·, .· ' ' ~· .- ·.·. ;. ,· ·':i ;_. i' ' -~ . ~- ' . ! \, i; It·,. I,, ; ·, ~--: ' .. 1 .-, ~ • l l 1 : i ~ . .: ; :twe .like it or not, they are always present as impurities and in all our t . .. :, . -: r -~ ~ .:- .· . . . ;.. , - . . ( . . . . - . ~ . '_:_~}," .··' .. ·\" :·. ·. '. -~... ~- '. ~ .· . . ·.. ';.... ~;.' '; + . . . .\~! ;{;tubes we alw~ys ·_see spectral lines due both to neutra.l Ca and Ca ion. : ~-- ~- ~- ·!L.-.. l_;;_ :_· _ t !" -· ' • ' • - . • . ; . • • .• :, - . • '-. ._ : ! ' ;_~ t, ,' -·::' ' . } L .. · '·.we find;, depending upo~r the metallic impurities which fix, the electron •· :. ; -:.L:~ ~ . ~-- ... ~-: . . -< ... 'lt.:.·,·· l ;c_ '-,:' ';-:~_par:tial pressure of our ~;stem,; that; the ratio of ne'dtral,calcium to . ~ : . . . . . ,., : ' i'' ~ ~ ' l ; ~ :_ . ·. . . .. ! . -·; ... '''l · : ;-,,~;calcium ion .varies.· r. • :~ c~ .. ~ .'- ·i'" -~ ~; ~: ; ( . ' { _;:, '.f;.. We did a series'- of experiments 'where -vre kept the_ ca:r:bon activity .: ·l·,, .. : :.: .~- J. . :··-;.:~' ;{constant~. r· the -temperature. constant and varied the ele:ctron partial pressure. . . ~ ' : ~-~ ':; 1. ' • • ~ ~. ' -~-~ i t - '•, l-as measured by the ratio ofneutral calcium to calciUm. ion intensity and ~. ;' ~ .;_-;·;. ,'- found that the c : spe9trllm; aid not vary inintens;lty._. That proved that' 3' . ' . . . . . ··. . ' . ; ; , :' ).. ~ t was due to the neutral mOlecule. and essentially' assigned it Ul".ambigu-.' . : '·> :~ . . . ; ~ . l' .;:ously to c3. This is something >vhich. must be done be, cause we know from · .·. ·· -:::mass spectrometer work,_:t~t t;hern\!ll ions are present.l, : I~ one takes any. _., . .~ : _::, :1fof these· high.temperature vapors>and., instead of:bombarding with electrons ' : ~ -;~:-~-~~~: :_;; .!:j_~s ~s customarily done,_ iLt one a:ppli~s ~n ele~tric -t{,eld :to these high. -'•' ':,.· \J;temperat~re :u:apors 1 ali .sorts of io~~{positive. ada: neg~tive, can be . .'' 1 I ',:; ·.j; :. ' ' ,~ ' ~: ; • · ·. ·,;, }_fpulled out. ·.So we ki:low that the.'equilibrium vapors ~ave,.: :i.n addit-ion . . . ·.·.. '; ' ' ... : . . ·f- \' ~ ~ ~ ; I . :.· :):to the multitude. of neutral polymers I talked about ·~arlier,·all sorts of i • ' ·::·f.; I'' ' . . • • • ·, ~ - . ' :. •:: <· .. 1i_;;! ... · .. · l·, t.· . :.·d .::;:positive and nega:t-ive ions ... '' i ;::J;iJ!!· For very hi~··t~mperature.·carbon.vapors electric ;fie?-~s)hav~ been: iJH!used to draw the ions into a mass spectrometer and :the existence of carbon ';•: ·:~;~~io~9"-~~;J3).:~~~1J.· ~lus an4 minus wi~h up t~ twenty d~ms ~?.r more bas been , 1 :Jilirmon:y;:~ow, Next question, p~~ •• : :. • .• J: ·~ · ; 1;(:! DR~ EYR!N~: ;:(~Roy Eyring, Ar+zona State ·trni~ersity, Tempe; Ariz6na:) · :~·. : <;·;·~-~!} ;· ' :'· ':· :'' . .· ·.·:'' ~' :... ·.. : . ' . ;. ''· '' .' ·... ·~· ... _·. !.., .. :.. ~~:·l .. ~.-· .·.' ·, . . . · -.· i ·. >,J;~:You h8.ven 't mentioned., Leo,· the s.olid state at high ;temperatures •. I . t..:,. ;,;i\ .. . ' :; ';: ··.·' _; :: ·:, ._ ..·· .· ' ; : . < ' . . ,; >! '·· ;,: r> ;\ :.-wondere4 ~0 what. ext~nt it is :important 'to :define- tl:l~ state, the solid ~ .f· ': ·.:> i-:: . ' .. t:, ; .. ;.;·state, in these :lll·gh .temperature ·ccmsiderations and to what extent the· ., ' : ~apor species may be dependent .o~,_· say, -.the coordi~tion or the particular· ·.l ,; : <;. '·J! ...... __ -----:---..,.------~- . ( ~: ! · · ..:-. ; ~: ~ . \•: .: .. ; . ·:~~~~~~{.: ., •;t__ •.·.·.:\· ·'' . ·: '; 'Jj:l .. . . -50~ . _;;. . •"'!'. ) .f. ,,· ·.. : ':(~i[. . ' ' ; . i · . · .: :.· ; t · ':r'zhicrostructure 'of these solids at high temperature? , . _._, -~ l' ~: :_-_; ~· ~-~··}···i ;.i •• • \ •• : • - . • '-! " . i . ~ ~ ~:· : . : .. ... :,".: i\-:·; ,:; :;C DR. BREvlER: That's extremely important. I didn't mention the solids '•' 'f ,.;· i ~~·,:!:~tall because i' didn't 'Want t~ be here until tomor~o~ morning,; but that's ·-~ ~- . 'l ~-·'t ,t ~ ::; • .~; ~ '' · : ·l "<'another whole story and of course it .is extremely important. I can list .; t· ":~ t , ' ~ '. :: s~me· referen~es 'to o~ work with soiid;;8~9/-~s seen,·from semiconductor ,1~ .~ ... ~::t~ · \ , ; :·:work, the· characterization of the exact composition of not only the major I. ; { .' : ~ : .f: ' : . . . .~ . : ., . . . ·' ·. . '·. 1 .: . q ·· ,':;.;;elements but .also· the. minor elements is very _importap.t. This is so far ;f ' ~ : -~ ' • ; 1 . ' . -: :: r iquite a few properties. It is equally important for the thermo¢iynamic . ';.·,. !''' . t ';! ,.,.~: i r; ; (properties as well as kinetic properties. .. ~' ; .. { ! i' ~. ' . . ' . . i : :; I \ . . ~ .. ,. ·,',:':literature. reports of a measuretnent ~fa: vapor pressure of a pure oxide~ ·.' ~.. ' ·. I . . , . . . ~ .. ; . : ; · :_;: .;~o~lly, the. measurement of the vapor pressure of ·any material' is meaning~ ; , .• ~r ! ! ~t:U~ess unles~ the syst~m is rather uniquely defined. One m~thod of defining <'a system is to add a second phase. · For example, · to claim to have measured ' .. ..; ·'· ;· ..: :) .: ;;;!ihe vapor press~e of pure ferrous .oxide is 'compl~telymeaningl~ss .. Ferrous .-~ .~f! . il ·;p,xide, as .well as all other ma~rials, ha~ quite a range of composition,.. ; ' ' 1.' ; ''!" ~ ' {I!o do a significant eXperiment that someone else C ; :·' : ! ,, I I • • " ' o ~ <:/~terial has vapori:zed);he vapor and>heJ con~ensed' p~se reach the same :.··:;,:,',.l .· ..... · ' . '- . . ' . '. . . :· ;, . ' - . . ' ·:: ·• l ; . .-.··. ·; ,· ': .·· ·-.. . ..· .. ,· ,._ t ... ,'; . ; . : : . ·.. ·. ; :· .compositi'on. :Then the .condition. of. equa.l·composit.ion :1n two phases introduces -~ : ' • ,- • ' ' ' • ', ~ '•: ': • ·: I • ·, • • • '• : - • • • ' ' ?; • ~ f l • • ' - ' ~,': . . . . ·- .. ·: ..·.· ...._.~= .. ·.. :' ~... .·. ·; '·,: . :; .· -~ . •, ~ :· "» _:- '.. :' •• •• ;; ~ •• • ·:•• I . ···.··:: ·· : ~other restriction :t:Thigh ··fiXes :the system, even. though there is one . ~. : ! , i ~ ; •. •. '· , . ' :. ; ' (' :: '; • .: ·' •: ,, ~I } • • ' 1 ..·; •'. ,, '~ ; . r r l: .-~. i . : ~ ' ... -51--. ' ( . ,. "i . ··. ' ·: ~ ,·., :l . .•· ·I .. ~ . .'::. . . '· ' ' ~ .. Finally on~. can also untertake·. the very di:fficul~ task· of determining · :.''-,: :' .... ;, ' ::: .,._ -d . ; t\ :!:;t~e exact compos,ition of the single: :phase being studi~d i:f' one ~$es a . ·: ,;, ...... ;:· . ~ :4 o'. ·r,·:~thod of ~p-oriktion that doesn~t- :change that composition appreciably~ ; . . . - ·~.; f ~ f • ! ---1 .• ; : ; ' ~ ' '- " ' . "-• .,;; .. : .. 1'his is a very important problem •and of'ten is quite neglected in data • ' . ; ~ ~ ·, ~r I :: :recorded 'in literature. · The data :are- qu.:;te meaningless unless the system .· .. .. . :, , ! ::~hat has been studi~d is uniquely :c~ract~rized by t~e ,phase ru.ie . l . I ,. ···_, 0 - .j. j · DR. ROCHOW: Someone over here on my left- had his hand up. : ~ : 1 1 : ·~ I f . ·. ' _;.. i . . ' !' . --~ i , .: ; . Dr. 'Haber • r 1.• . i . ') .. l ri·; ·v I ~. . '-;· . : : :~' L { .•1' DR. HABER:. ·Charles Habe::):',. Nav~l Ordnance Lab·.· ... ~ 'l : };<[! i '· 'I : :: ,: c; · You. stress~d the; fact at·:·.the beginning ~:r the talk that high temperature ,: . 'j ~: ., ' ' i ' L • , i ' ' } ~ . ' ' ' . . ' - .. .. . ' . . ' . ; · meant, in addition .to. simple mol,~cules, very complicated. molecules. Those ~ ; ; i :_ ;. ~ . . ,' ' ' . . , . '. ; . : . . ·. 'o:r us used to working near·room·temperature think of the e:ffect.of '. _.temperatures as breaking off small fragments and e:ffeci:;ing depolymerization .. ' ; : j i . . . ,· .. · . : -:wherever possible~ . Is this solel~ due t6 the fact th9.t you are describing . -~ " :; i . . ' '•". ·:. ~ ~ : ' ~ < j • . . ! ~~ '· ' I ' .: ~- . •, .. ·experiments· where whatever pressure is develope . ' ' . ( ' ' ' ' . .. ; : . ·. ~ ~ ) ' . ' ; ' .. ,f ·i, .. not remain constant• ·Although, it isn-'t obvious: .in .detail,: the result one .. ;- i ' : : .. ' . ' l . '\ \ . . • . i · ·· : ~-. obtains from ,~he~e calculations is t~t the pressure :vrill aiways rise t:. ' !. 1.~-~~f:·~ .. . ;~ . . . . ,: .1 ..: .• '-~. ·' •.: ~-;· -~~ · ,.'1 :'fast enough -to' compensate for the effect you would expect of increasing:· ,,·J~:t·:· ... ~:~~·-~!_:·: '· i.:·:·' ·:·.·'_.·._.·. :· .• _... .:·~_·.: .;.1~ ·_ ....··' ' .. :.·:.:.: :).,. ·. •! ·; · · . : .;~j~emperature: if it were carried out at constant :P:tessure. · ;: I ~:. ' ' ~ . ' i .· f !, ; • • •• ' . . • ' • : ·, • . .. ;; 1 1 I. ~ . • i i . h: T!l: You see, where one is misl~d.\s:that "one would':px;edict that incr~asing \ '1 ~ : ~ ; . 1.\'i: : . . };(.;t~he. temperature_:~'£ a system at co~s~t ~ressure w~·~l~ reduce the complexity. ( ·: ·;:~!:;:But that would mean ha.Viz:ig a gas system by· itself.\ :':rhe problem arise's in l 1,;Hi':. .. . .· .... :'>:·'· :~ . ,_ ·:· ·. ; :: high temperature systems :vrhen a· gas is heated at _constant pressure in a -: ··, ··:.:: !' , ' . container. ·· · The containers are' ,never inert arid· what ·will happen is that the :. ' <' . . ·.. <; . !( ~ : • .r ·. :; ·. .> • \: ,··: ! ·:· .·:·•.·.· . ~ ' t.; !' :· :, ." ~:: I I, ~ I ; i ;. i . ') i . 1' ,! ~~ ( .... ·' • • •! j_ . ·~ ; •' ... '., ! • ~ '.·.. '~ ' . ~ ~ ...... r: -. ,i'; •: "I ., -:>.. '.•- . ,; alyjays:: 'beco~s a part of t:k system. It will cont~ibute to :.·· ·.. : :1\he gas phase .t6 an iricreasing exten~ the ·higher yo~ g~ in: temperature.· ,'. ~ . ! '> I.' ·( .. ·\ : The. only way· you can escape.~·tbat is to go· to a c~mpletely gaseous .. · ' : . ·' •• : i : .• j ~ : j ·• : <·; :system where n·6: condenseQ. phases· oi. ~hy sort are pre s~~t. · Then you vTOuid ~..._~ :·.;~,. ..~ ; '){:go to simpler sy~terns as. you .~on~ihu~ to raise your temperatUre •. But i. '. <·: .:~;: . I' • . , .. in almOst ail; these .studies there is SOzOO condensed phase present. If that· ;., ;. ,, ~·.f. . . . . : ' ...... t. '· . t • • t • • ' • • + ." • + 1 ., ·; i:s so, then you_wiil 'find .d.nv~:t-iably'as you reds~. your .temperature that ,_.! ;._!· . ' . f • ' '; \.: ' :. i .~ •. ; i. ; ;: )the gas·.will 'become mere .· ':·!: : ,•, cpmplex~ . . ' :!. 1 . ,;.· . . . ·;\: ·' ::::: ::.t;i .l -, DR •. RQCHbtv: :Or. Sisler? ·· . ~~ ; ' :, . ,.. ; . ; ( ~- . . ' •,' . ~·. . .; , ;I '.; ' I ; . , r ; ; , • .t,: ~ ( -~ t '1; :· DR. siSLER:. ':ts it true, though,:, id"t;h ~espect· t~ ,the examples that ~ • : '~. ~'' ' ; : ) ' I' : • ,' ' •'· . . ·, . ·, , . . . . I . ~ i you gave us, very complex moleculef3 such as the -:those vrhich are polymers ; ., ·,i.:: • . ' ' . ' ' .. ' . . '!f. ·.· . \ J' .. • , I I! , ·o:f ·Mo03' :if \o _:use ·the. term 'tV'ay, do not all refer to ·'·' .!:. Y~\l 'Y'~~t ~hat ~h~.~~ : ·.. :' ~. :; · ,:<;,·'situatioris;whete.eve~·-·with the 6onli>le~ities of' the. sp~cie~· which you li~t ·.: n ·1. • ·(> . . .. ·. ·. . ·.• - ... · . ., . . . .:; .•...... '\ :: \i ·. :·i!l the vapor phase 1Jh~y ate still less complex than the s~bst:ll.nce which, . . ,! ~ ';; ';;' i '. . 'i • l ·. L;; :;.~~ists in the' .solid phase with wh~ch: ~hey are in equi,.~ibrium? So that .... •' 1 •• : i :i::i\rhat Dr·~ Haber has 'said- actually has resuitea:·:in the· ;f:*agmentation. ·;,!.; \i~~ther than .the c~mplexation of the process. · .· · ; [ :· f '! ~~~~ ll)l. BREWER; :;1 am not quite sure: what you mean ~~ th~ substance :Ln ' ithe soli4s~ That~is,: you haVe·'an iD.f~nite molec~e:i~ ~the: solid. ,, '." 1 f ' ~ c' 1,\ ·.. , l~ .> · : .. !· .,. . , , j' ~ . _. . :' , ·. l· ·. ·~. Hr . . . . j ·r: ... : · ~- ·; ---~:. ! . r.< i.:f:.L :·:?R •. SISLER:,,, __ ~o ,·.. f~:'.exrunp.·~e:.·H· :;• ,·; :-.{~n,·i:· ·:: . 3 1 ,. . ·:. ;,'.f.;.·_:,,· .. :.i.· ' ' . - . . ' . .~ · , DR. BREWER:_.;)-1oo is a ·;~'rt.. ~iho:: species.; ':r<~9~ ta.fe: ·-·.-. i .. , ·. ·.'' :pp,: ' ·.· 3 . . . ' ' . ' : ''' ... 3 :;~~nsi::· i;::~!~:n:r ;mys~~~ tar;.. C~stm [r Mo0 . dOOs. not . : ·-r:i Tf; DR. BREWER:·: /7-~tt~an ~nfini~~~ lattice.. . >!::f·f . .. 1 .,. [ . . ~. .r 1 ~' :!:fi! DR. S~~LER.: ':·T ~~ ~o~t~oll·o~~ Mo3o and.~49i2".~d; Mo o . corre~ponds ' 9 5 15 1 ·.. ' . ~.· :· ••r i~ ri:agmen~tion,;.'\~ ~ger ~~c~, ,solid ~d3 : ' . ; ·• i ·. ' . DR. BREWER: . :• Oh, it you like.isir. ·· : , : ,-- . '· ' . . . . . ~ ' ~ ·' ) . . . ~· . i . ' !· Lau~ter) ~ · ·' .:. , .. r •· ·< {. \·• '·' : . ~. ' :f ~- .<; ' . ,_. ·. -' .. ~ ,, • t_ • • • . '. \ :\ t ·-_:.· .. ' • \ !• . ' ; ~ ' .. -~ ...... ·.· 53' t,o· -~: ~- . ... - ' - ' ~v ·'·. ;t! ·- .... · ' ~. . . . . ; 1 ~- : . ·:·:·, .... '.·. ·. ·:. ,· '.I,. . ;. ! . ' ., the vaporizing s:peci~s andit turis out to be a very minor species. :The j ' • -~ ~ • .v" .·! . ' , ·i :major species is_ MD o , ;.~hem coz:ne.s ·~ ol2, then MD oi.5' 3 9 4 5 ~d :f'injlly~ _Moo3 .F(i ~ . - ·;; --~- ;- :. _. · ; , ·· ·.. ;· · - -~ · --; '! \ ;. ... -!.'. ;:;~d ,Mo o ,·_i:I?- order.'. ,. ' '; 'l: ; ' ' • ! . 2 .6 - ·-.' ._. :. ~ ~ •. '. . ,ill DR.; SISJ;.ER:.·;'M.ay I' ask a :t"ilrther question_? Is' the temperature rising • _;· ' • • ·. ~ • I ) '. ~ . H: :'·as the s:pe.cies gO trom Mo o to. ~10 o ·to 1-10 o or _dbes ~t so in the reverse .· 5 15 4 12 3 9 • :.; ~ : . ~. ; :" ·- \' . • : . : • ·- . ~ . .. ;~ l ~· .. :_;;:j:}~rder? ·..· ·'' ... .. , f. . , .··~ : ·: i · ;: t .. ·· • t'· ,~: :H:;. •DR·. ,B~WER::: At low temperature~, -~ 3 o9 is the ~st ~~undant; this is;! ; . i, now in the. vapo; :i; e,q_uilibrium· wi tb.' .the •condensed p~se. ~· ·As ·you raise... ,,.I, .. j_-''. .-.; __ : .•. t. · J+he temper~ttire .. 'the Mo 0J.2 . and the· ~ o keep gaini~g -~~- the Mo o , , 4 5 15 3 9 ! l \. . . ; ~ )~ ~ . . ' . . ' ,; ,:: ; constitutizig a larger and larger percentage of. the vapor. :So. that i:t' you !··~~.}~.~-;.~ 1: .· .:. :·:' -~';.· ·,,, _.:··.:~·- ·:_:.: ..... _ .. :_ :::.· ,..· .. · . : .• ·_.· :· ,·, ·:__ :··· . ', 'ywant_ t? get the largest :proportion o:f' Mo50 .· , you go _;~o t~e highe'st temperatur~ ·. . . :t : . . ·. . :.· ' '...... : '( ' .. :.· ' . ' ' . '. 15 ; . . ' ; . . :. ·: that you· ,can reach and still ma.int~in the · condensed phase.: ·:: '-qt ') :,: .. DR. ,aoCHol?(rl: pid I undmtan~.' Your reply; cod¢c~ly be~ore to mean J;li~~t t!Usi~ t~.t~d that the ••rmical. s~tem bas wrelievi~g its own .... .r · ::;,autogenous.:pressure?·'It combines to ma.ke more com.Ple:x: molecules, thereby . ' ~ i ~. ~; I •. : • .. ' . ' • . ·. .' .' ·,· . .' . . •. .. , . . ' . . . '• [ j ' ' , :.:,( • , . .. . :_ ' ·, . . :· Tt~ducing,·it~ .~o~-:~:por·p~e~sure?· Is that a .fair ·sta~~nt?; . ; ' ·i . ' ~ ·.··········::·:l·····l,:.::... .. ·••· 1 <.:· .. ·_.. . •...... •. .. pl.'a,se? : a re·s·.:ult. ~:._:.~ _ , .. ~ :n•.:iR-~.- ···BBRRE~~: · : );·~~t~;=~~r=::>~: ~l~ You see, actually, the ya:por :pressure yo~ get :as , . ~-. . - I _: '. -~·-~- J .. : "·...... --~ .. . ··: . ,· . ( . : .~ ~ :;\/of these COIII.Ple:x: species. is much hi~er than you woulclant.ici:pate, say on the.·.. ·;' [.t~_,;;·:~· ..·.·· ... ·,·.····' · ... ~ ··. ·~·;.• ·.:· ·.,. ; of had: way o,f .the stability o:f' Moo :~ -i~tsis. ~93 ~n~mer.: I~ y~u s~~ :predic,~~ng 3 i·::L ·#nomer and had ·::· {. ! ; ::!,:,: ' '. '' :.· i ; .. -~ i -·-- ... ·.< . ;. ·· ;~I , . · · . . . . ! \ "" ~ .. :t . . • ~ t . ,, . . ·. ·~ :;: ~ . . . ~ ; • 1 ;,._,, I. . ' ·, d ~ .. ' ~ .. ·i -~- ~' . . ' ~ ~ '' ;. .( ·.• :'' ~ ., ' ! ., ' ~ . :. ' ·, .. . ' . :' .· ... ·· ,, ,. '' .' 1· ·~· ·.. 1~1 ·, Is that·. clear? · . . ;~::: ...~ :~,:.}· .. · ·.~. ,._, . . i~ :\ . ·.'rf ' ~- ). . ··.· .· ' . /' ! . ' < '; :- ; ~ l > : ~ : DR., ROCHOH: ,>Yes. ; ...... --- ·.,.,_ ' 1 ~- -·' . ,_· .•. i '{' "'f._ ,.;·.. · > One mo~ent, pleas~·. · A· question ,up here in the front :row. >.. ' ·. DR .. SPEDDING:: (Iowa· State Univ~rsity) · Hhen ·you: are measuring the '. ' ' ~- . as- present in. t~e gas pha.se at higher and higher temperatures~ .go:Lng .·• i ~;-!;:~om Moo :three .times. to four ~imes,· 'of course you hav:e exicted lovrer · 3 ·;. ,i·' > 1:.:. I ; , ! '•' f •i <. ' . , ;):levels and since the actual io~est' state of .that pa,rticular mo~ecule may.· ''l ' ' , _: i ~ I .·;;,be an excited. state.asvell as·the'ground sta:te, do jou get·the.same ~ ' ' r;: ~tructure 'for ,this polyi!Ier, or do you have a. whole ~~.ries .Of polymers of. ~- .: '.' -~. -~ J':' '~: 1i 1 . . . . i . ·;: . ' . . ... ::;the same composi~ion. vtith different :.angles ·and so :f'orth? ·'.': ? ' ·.DR~· BREWER:·:-· Undoubtedly .tlie higher eu;ctronic ·~tates will have different ., ' I.~ ! structures·than:tll.k 'gn;imd' s-tate~,' so. tha,t: you will :b.ave ;~ variety_ of ,,.·:;·,::· .. i ' . ' . .. ·. ,· •.. ·.:f. ~ ·: ,I \. ~. -:-..; ; ~ •, . ,}'-' structures •...· ..;, •,' ' 1 ~-' i !:•: ~- ' :·:' i ( . ''!_ ' ·: ~- :: .:, '; .. ;, . >f . . :·l · w~ 'b'o~r thai a~eady·•for··:just:t~iatomic melecules." -'There· are many·.· . - ;, ~. . . . . ' .. ' ' . . .. .-)· ~...... f ) ;·; .; ~nstance,s, wb.e.re 'the ·ground sta.te is' linear and the> excited: state is bent ' ,-. '•' ~ ' . • • ." ·, .. ". . ' . \ t'. ~ ' ! ; . •' . . . . ·::~:-·~;}j:_ . f ' ;: • '·:.~ ••. '•·<>- '!J' ··:~~:.. ·-·~ , i<: and vice versa.. And you will have comparable changes 'in .structure in the ~::l·~·Ai; ··:--: ·-,.: ..·. ;i. . , •• ~~~. , ... :::r!:kor~ :coxi:Ipiex molecule$. ; '; . ·:: · ) ~ ~- !{.' ... I -_~;:,;!,t:.~;.i··.·; _,_.:.-_ ·:_ ':.•:~ · __ : ·.>·. -~. ; . ·----~- ~-:.· ~ .·· ·. '. /:; :·; .. ..;: f _'; -~-: . ; :~1 It will affect the overall partition function •. i .. . ';~~f.! .. ·... j •· · • • ·· • r-.:~ .r~-~ . ~ . ~ ; .; il?t\ · DR~· ROcHd'trt: ··' Y.es, please,: Dr.: prgel. ,.... ' . ·~ r Y!i.\ ·DR:; bRctEi' ;:(:U~iversity 6~ C~~{dge, ..Cambridg~·J . En~land.) I would (.:· f-· ihfl! ' ., .'., ,. ._. ~ ··; ...... ·. ··: .- .' > •• ,' ':; .. • •• I ,·.··.' 1. , .·,_; .. ·. ~- ;~ L~.LH !·:· _: . ., fV.);f;ljust like: to :~sk a. simple questibn.;; The ans-vrer. ~s ~~obably obVious 1 but ·'·.j !•i:iis 'equiiibriilln ~J.wa.ys reached so r(3,~idly over a soli~, that the species in .;.~_ '.!_j_--.•.:.~.~~-----.:_'i!,~_',,'.~-~.the gas Plla~e·.~~:x: .; sOlid_:_··.. rTh.epe·_ree.xasenm~lteru_.o·_ef. : erqe.ud·i~hoibrs_pih~olr·u· s:.·;,; i • i ~17,' . <: DR. BREHER.:;· ··;;oh, no. ~ ~ discussed earlier,y" · ·!· ·,·· {lil~s a case\here J' : .. . ' ;·l~··::'}_::,:.: .~~,,_·.·t ~ ·•· -- .- • ; ! .: ~ : !l' " . :. ,;··. ! .: f :·!~ -~ .· .·, f , ·r' .J. ' ~ -. .' :·. ,. ·.· . ·~ ~·· l: ..\· ; ; . ·.: . .'~· ·' i ! . •.! ; : i .', .·,· ·, i ; . ~ DR. BREvlER: · _ Well, the carbon ~roblem. is a rather interesting one. : ...... ; ~ :.; -!. ~ ,j 1 ·i·j;\\\ DR. :~l1GEL:,·: .~;a.m.really.t~ih,g~? get at th~s: ~~m rather a theoretician s ;;point or view~ . What I had in mind is: . Is there a problem :f'or a theoretician ·; :; ,: ; : : . ' ,. ·. ·.· ~· . ••. . .•.. ' : : >. ·• ; + . ..•. · i . • ' : . :: . . . ,! i .:¥ try¥lg; to explain why .th:ere. is some c20 .there in t:erms .ot the three f .. . ' . f ~ 1 : . . -~ . ·,' ' ' .. . ·. ·' . . ' - . . ' ' ~ ' . . . ' .- ' ' ' : ~ ...... ; . : ( : '. . ;:p,ossib.le structur~s~ electronic and geometric and- or is. that·-·- ;;·\))· ...DR. BREWER:.:; .Ohl :·,yes. 'pi~zer. an~ ClemenM/diO. ;that. They have . . . . t ' • >• ( .·. :'publ:ished' a pa.pe~ .in which they ·~ve barried out a •molecular orbit treatment ·, . -~ ' :, ~ ; I :, ' ' ' . ," ' . ,· ' ,t : ' • • • ' '· :~. ~; ; ' ' .- • .. ~. \ '.dtail the .. :They .ha:v:e· pointed out that ·there·· should:· po~;:i.c ~rbon.s:pec:i.es.'•~ - . ~ ., ·,.. j . ' . . • ' . ' .· c • ' ' : .' • ' ' ' •• • : • • • • : ., • : • • • • ' • :: : : •• • ,. : • • • .. • ' '- '; . ' ~ ! ~ ' ... ! '~~ an alternation: -ill stab:Ll.ity> Eve·ry odd-nmnbered ·n.~utra.i c. ~lecule ·would . · .··r :.;· · · · -· ·· · ·.. ; ·'· · , · : · · : ... · ~- . ·. ~ . ; _:· .. _. · ~ · · ·. · ; . ~- ' ( ' ' i I :be extra stable and every ·even n\.U!lbered species WOuld be extra stable i:t' .· '• ' '' ~\ 0 ' • ' ' ! I ,·, • ' ' ' I '• ' ' •~ingiy ioni~ed, .ei;thet;pll.l.s or ne'gati~e. :·Their resul~~ quaiitatively follow· .: .. !:~.p~etty .. wellwba~·.i;s,t:o~d:·,.:one:·does, ·~in~· th~s ·a.lterruiiion''in ·s~bility. or· .• .:·. L.. !} '' ~ •'-''· --:-~·- ~ I,' (" . '· ; ·.. ' ': ... .. l;; . •, ~---·: ·, . :·: • !_ ' . . : '.' ,' ; .... i -~ ' ~- ·' ·, '•· ·... .'' .. \ ·... .:.56-:-·, I.i , .. c' •r ;:- ~ ' .. . {·. '. ,.,, .. ., ,· . I, , .. __ ' ~ .- .. ·-·.J . . ~ . ~ .. '\ -~ . i .. ,. ~ > ._, ~: .. . ; DR. · Dr; ·E.yr:i.ng? :. . . ·' /;,, ' tROCHO~[: ~ , . __ ,(.. ... , . ., ·, ' ' '" ,. ,J ''' .....·' . :_1 . ····;·Jt· •·:. '.-. ;, . • •,y-~ :_:· ·.. ; ,' -~ . :; {. I:'·: ;. .. .. '· ~ , .).~ '·j ,•; .. :.!,;}~~ ·th~~::~:o~::?: ::z:· ::~::o:~:::Ji::a=:~;~.re~pect • .!'~ ; .····:·<::·:ethan~ on ;the basis· of knowing the ~~por,;press~e 'of:c~rb~n~ (laughter). ~· H 1 ).;.~. It's ~he, pe~nnial' question. ;, •: i; · • -: ~: • _; • . .. • ~ . J l -, .· .. ' ~.: ··• DR. BREI-l.E;R:: ···.Hell; there is. no question about the ·.heat. o:f; sublimation. ,_ i . . ' , of carbon, ,but wMt carbon-hyd.r~gen '):)'ond energy d~· yo~ WaJ;lt me' to use? • •• • .~' • • .;, -~ '• • ,-.. • • ." .•• ' _! '• ' , ' ' '" '.f ' ·'• ) ' .,.- I ' ' - . ·:· ..... ~ \ . ',' ' DR.· EYRING: . · I know.· . . , , · • :.• i · ,••'• ~. t. :- ., \·. ~-' ; i: t : . i ;r You' ha~ really answered the.'quest:ion,· .because you dO. say that you .: ~ t{! . . ~ ' ~ ·. ..; . .. ;. . ' '' . . ' ~ .:- ·. ; ,•·! really . .. think' " we knm·r. . ';;.._·. ' ; . . ;_. ~ ~ (. ' ' ~ ' .,. ' ·.. ' :. ·. ~ '·' .-i~-t:r ' ; ~ ;~ ; ~ .DR .. BRE~VER::. Oh/ I :think there is no question of' that:. There· is an · _I,.~ t ; •... ' . . ; ; ::.~certainty of about .so~ethillg like. a tenth of, a .. kilocalorie,. or thereabouts p1 :;:.~maybe two-.te~ths; .we have' it give~ in: our pape~s~Y ·, . ·~:?T;;! T~t uncertainty ri~es in a rat~er ~nteresting ~~~- .. ~e most exact.· ·) ; '\: ~~ ~ . . ' ) :;:!~ '!X~lu~ is .f~~,~ :f'r~m a ·predissociati'on >V'liich :i:s known ;~n t~e co spectrllin. •;q{ :Vis you :rec~ii,· the original controversy .had· to do with· intei-:Preting the< ''1 /~;) ::lir\ i •.· :. > < . '::' .~ ..; ' .•..:·· . ' ' : ' ' i ,. : ' •'. ' . 'r .. ·: ' . . i:·;( ;!'particular electronic states of .C ·and~. 0 vThich were .produced in the predissocia- . fi\-'~t:r: . ·..... ::: ...... i. ··:. ,, ': ;;tion. The: multitude of·variou~ equilibriUm. arid other ltype:s of measurement __ ;_..~::(-- .. ~r-H:--. - : ;·:· ~:- -·;-:.- ---.: ~ . - -.!:·_ ··z .- : -... ;. .-- i. ~- ~ :i-_; _:,:;, >:'-:.·.· ~)!! ' " . " ,··~·: .. ·'•. . I . : •.,• .. ' . ·,' • . ' .··, . <' i ·.:. ; H have. now .established that that predissociation corresponds' to forming carbon .... 't } :::;tUiY: . •· . ·... { . : <, ·.-. · · > ·. , < : ,; J ·. · · ·.·. ·: , ·• ) · · .· -' .··• .·· ... ·. · · ·:',):~·:.•}apd .oxygen: in the ground .electronic states. ,:But· there is :a. substantial· . f"·i<>:tH:: ; <· .· ... : .. . , . . .·> · <, . · .· ::· r: . · ·/·;.; t '·?sepa.ra tion: between the components of .the grol.m?-• multiplet/ and it, is. not .. ' i ., ._, ·,_ ., ~ ; .:'lf~,~own t~ ~kq116i '~~~{c~onent•s ~:' predisSociati~i ·co~re~po~ds~ so. ·' -·.·.:. :•.r~1_.; 1 ;JFere is ~:a.Il: ~c~~tainty. o1r th~ :o~~er ;of the ~ultiplet lsepa.ration of caioon i ·• l :i'~d oxygen;. and ~:t. the moment ·there.. s'eeriis:~ no :method· :i.r\. ·sight for sharpe~ing ·- • ·::. )·;,~---~.;:,. ~~ .. • < , : -~ ·.,. -· __.. ·:·: ->:-> . .. - ; i, .- ;- L . . -· -.. :_ · ;:_ l ' ... ! .· .··. ' ' . • ' . ·. '. . ; .· i .. ':1t up beyond :.tha;t~•. al~hough I :.hope :someone might; co~' :up vith sonie -vray of f; i; .: ' ·_ .; : ~ .: __.::.<. :· (>• .-.~-:-- .. > ' :: ;:: ; .. ,_'. . --~,- . ·. _.. -:< . ' ; -,- -~: ::+ .: ·_; ~:-- ~-~. :, __ ;_; : :: -~·: r. • ;: ;p?-nning that _dovm more .closely in the futUre.' .. ·. ··tj[ :. j:; ·. •~ >.~ ,~.t:' ' ' ·-~ c. :: • . •.. : :; ._-;·,-~< <~.::.>. . ~ ':, __···; I '. . : '~: '~-.~ -:~: > •'; I :;·, ;: ,: ~ ,. l ' ,.•. -i. ': ; . Hi ·But for all:practical pur:poses;,t.the :heat of1.-subl5.mation is. certainly. : ;~.·i:.:.T: . ·, i;i.-. · .·. .. • ' · · · . · · ;:; · ·· • · ... ·· •· · ·. • ,' _- •, I. ; ,•i .· -~ · .' ot ·_;; ': •. .r:!::· 1. ·-·~ • '~- : . ;; ·:.:1 '.', ,.. :, l'' .. , ".' / :<- -.·. l . -;·· "·' . !;: .... - ·.:·' ( '! '> ., r:_. , .·r ·~ .. , . •·. ~ . ..: '<' j ~ . / . :.. . ~ . ,q...... "• ' ) . . ·-5· 7~·.:.' ,.. •. ,.. ~ .·. {'· . ., ~ -<'; •• '.l. :. '; j ::t.· ; '; : -~ ·~· . -..: 'r. •.'• \. ,,.; ... ·r. ' ' . >~: . ,_ ~ ;. •'. . . i :; 'i . ' '' i}fixed accurately enough.· The.'. same is true of the: di:SsociS.tion :energy of 0 ' : !:\;~; ~hie~ had ~ s<,~i ~ t>rol>i.;.~ ; ; ' ', i: i, ... ;· '(· ·. ' } ' . . ; DR. ROCHOI~~·· Axe there any.:otller questions?' rt· . . ;:'! Yes, sir• t1illyO\:l get overi tb;the· microphone, :please? .~ ·.,...·.: • . . ; ·., ' • ~.,:,' i, . ·.-.. ·... Sorn: to each one .. of. you. to: take· the iong walk but it's the only ' . .ask· . . . "' . •'' .. ' ·, :,;-. ') -· '·--.·: ,. ' -~ ., . . ,. ,.i, ... ,_ .. · ,_-:·-