Ames Laboratory ISC Technical Reports Ames Laboratory
6-22-1950 Radioactivities of germanium, arsenic, gallium and zinc Warren Heiman Iowa State College
Adolf Voigt Iowa State College
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Recommended Citation Heiman, Warren and Voigt, Adolf, "Radioactivities of germanium, arsenic, gallium and zinc" (1950). Ames Laboratory ISC Technical Reports. 10. http://lib.dr.iastate.edu/ameslab_iscreports/10
This Report is brought to you for free and open access by the Ames Laboratory at Iowa State University Digital Repository. It has been accepted for inclusion in Ames Laboratory ISC Technical Reports by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Radioactivities of germanium, arsenic, gallium and zinc
Abstract Radioactivities were produced by the fast (pile) neutron bombardmant of germanium.. Chemical separations followed by decay and absorption measurements yielded the following results. Eleven-day Ge-71 decays with the emission of positrons with maximum energy of 0.65-Mev Ge-77 with 12 hour half-life emits 0.31 Mev gamma-rays. The alh f-life of As-77 i s 38.0 plus or minus 0.5 hours and it emits 0.68 Mev beta particles and two gamma rays. The following new gallium and zinc activities were observed, but not as signed definite mass numbers. A 14.5 day gallium activity emits beta particles with energies of 0.29 and 0.71 Mev, 34 Kev gamma rays and possibly X-rays; a 53 hour gallium activity gives off' 1.9 Mev beta particles and 1.63 Mev gamma rays; a 14-day zinc activity decays 'Wi.th the emission of 2.1 Mev particles and 40 Kev gamma rays.
Disciplines Chemistry
This report is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/ameslab_iscreports/10 Tow~ ' ·->- sc. ,. "$(~ V- AL 0~ 't.. - 1 />. ISC- \S' "-<,. ~·o 0 ....~ t""&f < ' RADIOACTIVITIES OF GERMANIUM ~ ARSENIC, GALLIUM AND ZINC By Warren Heiman Adolf Voigt June 22, 1950 Iowa State College .. l II Technical Information Division, ORE, Oak Ridge, Tenne,... Reproduced direct from copy as ·submitted to this office. PRINTED IN U.S.A. PRICE 10 CENTS ISC-89 Abstract Radi o a ctivi t i-es were produced by the fast (pile) neutron bombard- mant of germanium.. Chemical separations followed by decay and absorp tion me asurements yielded the following results., Eleven-day ae 71 decays wit h the emissi on of posi trona with maximum energy of 0.65-Mev Ge77 with 12 hour half-life amits Oo3l,Mev gamma-rays. The half-life of As 77 i s 38 ., 0 ~ 0.,5 hours and it emits 0.68 Mev J' -particl es and two IQ -rays. The fb llowing new gallium and zinc activities were observed, but not a ss igned definite mass numbers. A 14o5 day gallium activity emits f3 - par ticles with energies of 0.,29 and 0.71 Mev, 34 Kev (-rays and possibly X-rays; a 53 hour gallium activity gives off' 1.9 Mev f3 parti cles ani 1.63 Mev~-rays; a 14-day zinc activity decays 'Wi.th the emission of 2.,1 Mevfparticles and 40 Kev frayso l 2 ISC-89 Radioactivities of Ger manium, Arsenic, Gallium, and Zinc* by Warren Heiman and Adolf Voigt Intr oduction The fast neutrons produced in fission have suffi cient energy to induce some reactions other than then,~ process most frequently ob served with t he moderated neutrons used in pile bombardmentso In order of incr easing energy requi rements and consequent l ower probabi lity t he n, p , n, ct_, and n, 2n reactions mi ght be observedo The de sired r adi o act ivities can be f ound more readily if the therma l comp onent of the neutron spectrum is filtered outo Consequently cadmium wrapped samples of materials are frequently irradiated in order to study these activitieso Since the atomic number of germanium is low the positi ve particles, the proton and the alpha particles, would not require too high an energy to be ejected, hence, germanium was chosen as an element for studyo Also it was felt possible that certain discrepanci es in the reported activities for ger~~nium could be corrected and certain new activities mi ght be produced~ By means of the fast neutron bombardment of germanium, rath er high specific activities may be obta ined for the r adioactive isotopes of gallium, zinc, and arsenic, because the germanium may be com pletely separated from them by use of a special di stillation apparatuso The unstable nuclides possibly produced by these reactions would be Zn 69 9 71, and 73 by n,~; Ga 70, 72, 73, 74, and 76 by n,p; Ge 69, 71, and 75 by n,2n in addition to Ge 71, 75, and '17 by n, r o Daughter pro ducts could also be producedo *Work performed under Contract No . W - 71~0 5 eng 82. ISC-89 3 Chemical Procedure Spectroscopically pure. one gr~ samples of GeOz were bombarded with neutrons i n t he nuclear reactor of the Argonne National Laboratory., Each sample was contained in a silica tube which was wrapped with ap proximately 1/32 inch cadmium foil to absorb the thermal neutr onso The lengths of the bombardments varied from five days to two monthso Upon receipt of a bombarded sample 9 the radioactive Ge02 was dis solved in dilute NH4?H., This solution was then made strongly acid with concentrated HClo Zinc 9 arsenic 9 and gallium carriers were then added and the solution was t ransferred to a special apparatus for the distilla- 1 tion of GeC1 4 under an atmospher e of Cl2 o The GeC1 4 was completely re- moved by distillation and precipitated as GeS2 ., The solution remaining in the distilling flask contained arsenic, galliums and zinc., The arsenic was precipitated from 9 N HCl as the sulfideo The arsenic was filtered out and the filtrate contained gal- lium and zinc. The filtrate was made 7 N in HCl and the gallium was extracted with isopropyl ethero The galliumwas precipitated as Ga(OH) 3 and the zinc which remained in the a queous phase was taken down as ZnNH4P04 o The procedure for gallium and zinc was modified in one of the bombardments in order to detect any possible tin impurityo Tin was added with t he ot her carriers and subsequently separated by ether extrac- tiono It was precipitated as Sn(OH) 4 after the separationo Germanium Activities ~ich followed germanium chemistry immediately after 4 ISC-89 the samples arrived at .Ames had half-lives of 31 hours and ll days plus a low intensity 8 hour componento (Fig. 1). Reseparation 5 days after ir- radiation produced an arsenic fraction with a half-life of 40 hours while the sole half-life in germanium was 11 days. These results indicate that at the time of' the first separation the 12 hour Ge 77 was p:resent 9 growing 71 into its 40 hour .As daughter after the separation. The resulting half- lives were observed as ~ 8 hours and 31 hours since the de cay curve was not resolvable into its 12 hour and 40 hour components. By the time of the second separation the 12-hour activity had decaye'd out leaving only the 11-day Ge 71 i n the germanium fraction and the 40 hour a.cthri t~j in the arsenice. .A 40-hour activity is also reported2 for Ge69o This would have to be _produced by an ng 2n reaction in these experiments which is not highly probable at these neutron ener~ieso In the present experiments its presence would have been masked by the 40-hour .As 77 o .All that can be said is that it was not produced in sufficient yield to be observed when the second separation was run 5 days after the irradiation. How~ ever, if» as has previously been reported3 9 the 40-hour and ll~day ger- 11 manium activities were isomers of Ge 9 the former would be expected in large enough amounts to be detectable 5 days after irradiation. Con- sequently 9 our evidence confirms the present assignmente Supporting evidence was obtained by considering the sign of the particles as determined by counting in a magnetic fieldo The 40-hour activity showed a large ratio of negative to positive particles in agreement with its ISC-89 5 lopoo~------~ 5,000 ..cu Q. 1,000 en c -::;, c3 500 8 Hours 100 0 5 10 15 20 30 Days After Bombardment Fig. 1 - Decay curve of Germanium. 50,000>,..------~ . e~ 0.31 Mev Gamma Roy KDo~--~~ooo~---,z~ooo~---..300~o---.~~oo~--,5uooo~~ Thickness of Aluminum in m0 m2 Fig. 2-Aluminum absorption curve of germanium three days after bombardment. 6 ISC-89 assignment to As77 rather than Ge69 or Ge 71 which would be positron emitterso The 11-day germaniumD on the other handD gave a higher posi- tive than negative count showing that it decays to galliumo By absorption measurement s it was sho~ that a t?ray with a range of 1.0 g/om2 of aluminum. (Figo 2) energy 2ol Mev 0 decayed out rapidly and hence was mcst l:i.kely as so oiated with the 12 hour Ge 77 o This agrees with the previous value of 2o0 Mev4 for the Ge 77 ~ rayo Also associated wl th tr:.is decay was a gannna ray with a half~thickness in aluminum of 6o4 g/cm2 D corresponding to an energy of Oo3 Mevo The 11-day germanium t? r ay had a range of 230 mg/cm2 D energy Oo65 Mev. (Figo 3) ARSENIC 77 The only activity observed in the arsenic fractions was As for which the half-life was measured as 38 ! Oo5 hours 0 (Fig. 4) compared to the previously reported value of 40 hours4 Feather analysis of an aluminum absorption curve (Fig. 5) gave a range of 246 mg/cm2 (Fig. 6), corresponding to an energy of Oo68 Mev in agreement w.i t h the value of 0.7 listed in the Trilinear Cbart5• A portion of the arsenic sample was mounted for the thin-lens mag netic ~-ray spe.otrometer and the ~-ray spectrum was measured by E. No Jensen of this laboratory6• The value so obtained was 0.679 Mev, show ing that the Feather method was reliable. TheE?-ray spectrum showed a deviation from the straight-line Fermi plot at law energies, indicating the possible presence of a component with an energy of Oo36 Mev and a yield 12% as great as that of the major componento However, it is Dr. ISC-89 7 10,000 ~------, 5,000 Q) .... Q) c. 10.9 Days 1,000 0 25 Days After Bombardment Fig. 3-Decay curve of germanium obtained from the second separation. 10,000 .------, 5,000 38 Hours . 1,000 ·~e li .... 500 c 0 <>" 100 6 8 9 10 12 13 14 15 Days After Bombardment Fig. 4 -Decay curve of arsenic obtained from the second separation. 8 ISC-89 ~.~r------, 100 . '; 10 .£ E .~ 1.0 0 .1 Fig. 5-Aluminum absorption curve of arsenic. 300 E ·ec" ct" mg.-( 2 '""•246 / Om~ -0 .,E ~E 0.68 Mev Beta Roy £ • ...c 0 a: c: •0 Q. 200 Q. 0.8 ct 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.9 1.0 Fraction of Range Fig. 6-Feather Analysis of Arsenic. ISC-89 9 Jensen's current opinion that this is an artifact due to the reJativeJy t hick sample (0.8 mg/cm2) used in this case, and that a thin source would probably not show thiso Conversion lines from gamma rays were not seen in the results from t he bet a spectrometer, but l ead absorption curves (Figo 7) showed two '0-r ays of fair ly low intensity~ Ha l f-thickness values in lead were 85 mg/cm2 and 3o4 g/cm2 corresponding to ener gies of 0~05 and Oo42 ~ .04 Mev o GALLIUM Three distinct gallium radioacti vities were pr oduced by the fast neutron bombardment of germanium~ Decay periods of 15 hours, 53 hours and 14ol days are shown in Figure So A decay curve1 followed over a period of four half-lives indicates that the long-lived act:ivity has a half-life I of 14e5 days (Figure 9)o The 15-hour activity was identified with 14-hour aa72; the other two do not correspond to known gallium i sotopeso Several absorption curves in aluminum (Figo 101 and copper (Figo 11) wer e taken at intervals during the course of the decay. The aluminum curve s were subjected to Feather analysiso It was observed that Oo29 and 0.71 Mev .{3-particles and a 34 Kev t"ray are associated with the 140 5 day activity. The portion of the curves that is interpreted as t he Oo 71 Mev }? might instead be due to a germanium X-ray, though its intensity re la tive to the other components seems too high for this. The 53-hour act ivity possesses a lo9 p ray and a 1.63 Mev frayo The 10 ISC-89 500r------, 100 Roy ;:.. 0 - 0.05 Mev Gamma Roy u"' 10 0 3000 5000 Lead in mVcm2 Fig. 7-Lead absorption curve of arsenic. 5,000 • .!!• E 1,000 ...•~ 500 •"'0 <) 100 Dayt Afltr Bombordmtnl Fig. 8-Decay curve of gallium. JSC-89 11 IO,ooor------, 5,000 1,000 500 0 0 10 IS 20 2S 30 3S 40 4S so Oaya Allor Bombardment Fig. 9-Decay curve of gallium with some 38 hour arsenic present. ~r------~ so,ooo 10,000 s,ooo • I i. J1, 000 0.71 Mev Beta Ray soo ""0.04 Mev Gamma Ray IOC 0 100 200 300 400 soo Thlckntu of Aluminum In m.Jc;;;. Fig. 10-Aluminum absorption curve of gallium. 12 ISC-89 300~ ----~------,~~---1.6-3~M--ev__ G_a_m_m_a __ R_a_y------~------J 100 !! ::J ec: ~ • 50 ... 1---- 0.034 Mev Gamma Ray c• ::J 0 :l. () 10 I I I I I I 0 1.0 eo 3.0 4.0 5.0 6.0 1.0 Thieknna of copptr -~cm2 Fig. 11-Copper absorption curve of gallium. IO,OOOr------, 5,000 • ~ ec: 1,000 i ..... c::J 0 ~00 () 100 0 '5 10 15 20 Days After Bam bardment Fig. 12-Decay curve of zinc. ISC-89 13 f -particles were found to be negatively charged by observation of the counts t aken in a magnetic fieldo Consideration of the P-r ay energie s involved indicates that the 14.5- 74 day activi ty was either a nuclear isomer of Ga70 or unreported Ga o The Ga70 Ga73 53-hour activity may be a nuclear isom;r of or ~ or it may be caused by Ga74 o The assignment of any of the activities to Ga74 appears t o be somewhat questionable on the basis of following observations. Sagan.e 9 Miyamoto and Ikawa7 observed a 9-day gall:lum activity as a result of bombarding germani um with deuterons and assigned i t t o aa74o Siegel and Glendenin8 did not observe this 9-day gallium activity as a fission product of uranium. McCown, Woodward, and Pool2 attempted to produce Ga. 74 by the d.JrJ... reaction on germanium metal enriched to 70 per cent Ge 76 • However, the only gallium activity observed was the 14-hour period of Ga 72 o It can be seen by considering the isotopic abundances., the expected stability of the nuclei using the Bohr-iVheeler type of calculation and the fission yield distribution that half-lives of this length are less probable for Ga. 76 than for Ga 74 o In the light of this conflicting evi dence we are reluctant to make any definite assignments until further work is carried outo The possibility of the 53-hour .or l4o5-day activities being due to the presence of radioactive impurities was shown to be highly unlikely through consideration of the amounts of the impurities known to be presento The zinc fraction obtained from the fast neutron bombardment of 14 ISC-89 germanium yielded half-lives of 14 hours and 14 days (Figure 12). Beta- particles were detected with energies of 0.91 Mev and 2ol Mev (Figure 13). There were two a-rays of rv0.2 Mev and 0.,04 Mev (Figure 14)o The (-ray energies are somewhat uncertain because of the low intensity of the activity, however the beta-gamma ratio was 110, indicating that these were a -rays and not bremsstrahlung .. The Oo91 Mev J3 a:nd the /!1 Oo2 Mev (were shown to decay with a 14 hour half-life 9 corresponding to the isomeric transi t :ion (0.44 Mev ([) and )? ray (10 Mev) reported9 for zn69 .. The characteristics and assignment of the 14 day activity remain. Chemical evidence is strong against its being due to an impurity, though this remains a slight possibili tyo The 2.1 Mev j3 and 40 kev o ray belong 'Go the 14 day activity o The .j3 rays were shown to be negatively cp~rged by counting in a magnetic fieldo Ann, ol reaction in germanium can produce zn69 , zn71 and zn73 ., Of these zn69 is the 14 hour activity discu~sed above and zn71 is reported 8 10 to emit a r -ray of 2.1 Mev energy with a half-life of 2o2 minutes o From this information it is seen that the most probable assignment of the 14-day activity would be the unreported zn73 or a nuclear isomer of 2.2 minute zn71 o Of tha se two 1) g.eneral energy considerations could make it appear unlikely that such a long half-life could be assigned to Zn73 since the heaviest stable isotope is Zn70 • Also fission product 73 sttidies8 indicate that the half-life of Zn must be less than 2 minutes .. Assignment of the 14 day activity to a nuclear iso~r of zn71 might be considered to have some basis since 2.1 Mev is also reported as the 15 ISC-89 1,500 .....------, 1,000 500 100 ~ "'c ·e 50 .. Gamma Roy ..Q. "' 50 (.) Roy 10 Roy 5.0 1.0 1000 1200 1400 Thickness of Aluminum in m.!Jcme Fig. 13 - Aluminum absorption curve of zinc. 5or------~ i\o0.22 Mev Gamma Ray • 10 ; ·ec ~50 Q. "'c -:0 )ff------0.04 Mu Gamma Ray 0 0 1.0 0 1.0 2.0 3.0 Thickneu of Copper in .Jc"m2 Fig. 14-Copper absorption curve of zinc. 1 (-, ~ · ISC-89 energy of the 2.2 minute zn7lo The low abundance of zn7° (0.6%) pos- sibly canbined w.ith a low cross s~ction for neutron capture by this isotope would make a 14 day activity hardly observable in neutron ir radi.ateJ zinc compared to the fairly high activity of 250 day zn65 obtained from zn64 (abundance 49%, cross section Oo5 x lo- 24 cm2 ). Experime~ts are in progress to check the possibility of this isomerismo SUMMARY The following table summarizes the results obtained in the presen~ work. Type of Energy of radiation inMev )Juclide Halt'-life Radiation Particles ~-rays Ge71 11 days 13 .. DK Oo65 None Ge77 f3- r 12 hours ~ 2ol Oo31 As77 p-r 38 hours 9 Oo68 Oo42p Oo05 Ga70 or Ga74 14o5 days P- r Oo29, Oo71 Oo034 I r Ga70 g Ga73 or Ga74 53 hours p -II lo9 lo63 (Zn 71 ) 14 days p - a 2ol Oo040 ISC-89 17 lo Lo M. Dennis and Eo Bo Johnson, -----J. Amo Chemo Sooo, 45, 1380 (1923) 0 2o Do Ao McCown, Lo Lo Woodward and Mo Lo Pool Phys. ~o 74g 1311 (1948)o 3o Go To Seaborg, Jo Jo Livingood and G. Friedlander.~~ Phys. ~o, ~~ 320 (1941). 4o Eo Po Steinberg and D. W. Englekemeier N.NoEoSo MPTS Div .. 4 Volo 9 Paper 54~ New York McGraw-Hill, 1950o 5o \Vo H Sullivan, Trilinear Chart~ Nuclear Species, New Yorkg Wiley, 1949o 6., Eo No Jansen, Priv., oomrmm.ication, 1950o 7o R .. Sagane.o Go Miyamoto, and M., Ikawa, Phys .. ~o 9 59, 904 (1941)., 8. J., Mo Siegel and L. Eo Glendenin, NeNoEoS., MPTS.o Divo 4, Volo 9 Paper 53, New York, McGraw~Hill (1950)o 9o J., Wo KennedyD Go To Seaborg and Eo Segre,~~ Ph.l_!o ~o ~ 9 1095 (1939)e 10. Do Je Hughes~ J., Wallace~ Eo Goldfarb and c. Eggler, Reported in G.. T .. Seaborg, B.!!,o ~o Phys., !£,~~ 597 (1948)., END OF -DOCUMENT AEC , Oak Ridge, Tenn. , 9·8·50-67S·A27763