JUN E 1, 1940 PHYSICAL REVIEW VOLUME 57 Proceedings of the American Physical Society MINUTEs oF THE WAsHINGTQN D. C. MEETING, APRIL 25—27, 1940 HE 234th regular meeting of the American Hiroo Aoki, C. E. Barthel Jr. , Grant S. Bennett, Physical Society was held at Washington V. E. Bottom, Arnold E. Bowen, Eleazer Brom- D. C. at the National Bureau of Standards on berg, Ralph H. Caston, Robert L. Chasson, John Thursday and Friday, April 25 and 26, 1940, and W. Coltman, Rudolf Drenick, Alexander J. Fer- at the National Academy of Sciences on Satur- guson, S. Phillips Frankel, George R. Gamerts- day, April 27, 1940. There were three parallel felder, Edward Gerjuoy, Lee W. Gildart, William sessions for the reading of contributed papers on E. Good, Harold D. Green, William C. Hahn, Thursday morning and afternoon and on Friday Oscar L. Hay, J. Richard Haynes, Hugh F. morning and afternoon. On Saturday morning Henry, Marshall G. Holloway, George A. Horn- and afternoon there were two parallel sessions. beck, Paul S. Johnson, Charles B. Jordan, The attendance at the meeting was over nine Howard R. Kelly, John G. Kirkwood, Robert T. hundred. Lagemann, Joseph Lempert, Cyril E. McCellan, On Friday evening the Society held a dinner Donald B. McNeill, Charles R. Mingins, T. H. at the Wardman Park Hotel attended three by Mueller, Koju Noguchi, Shuzo Odajima, Anton hundred members and guests. President John Petrovich, Joseph B. Platt, Frederick Reines, Zeleny presided. The guest speaker was Pro- Philip S. Riggs, George B. Salmons, Chalmers fessor George Gamow of George Washington W. Sherwin, Arnold F. Siegert, Milton M. University. J. Slawsky, E. Howard Smith, Gail P. Smith, Meeting of the Council At it. s meeting held on Maurice R. Smith, Arthur L. Stauffacher, Franz Thursday, April 25, 1940, the death of one fellow David (A. deF. Palmer) was reported. One candidate S. Veith, P. Wheatland, Gerald A. Wrenshall, and Violet was reinstated to fellowship, one candidate Wu. elected to fellowship, and five candidates trans- The regular scientific program of the Society ferred from membership to fellowship. Fifty-one consisted of 179 contributed papers of which five, candidates were elected to membership. Rein- numbers 2, 19, 20, 55 and 57, were read by title. stated to I'ellomship: Ernest Blaker. ELected to The abstracts of these papers are given in the Fellowship: Gleb Wataghin. Transferred from following pages. An author index will be found Membership to Jiellomshi p: Felix Cernuschi, at the end. George B. Collins, Elbe H. Johnson, J. K. Knipp, HARQLD W. WEBB and R. S. Krishnan. E/ected $o Membership: Acting Secretary ABSTRACTS 1. The D15raction of X-Rays by Liquid Argon. A. EISEN- could be found beyond this and up to sin e/P =0.75. Keesom sTEIN AND N. S. GINGRICH, University of Missouri. —The and de Smedt' observed peaks at 0.159, 0.231 and 0.371 x-ray diffraction pattern of liquid argon has been obtained using Mo filtered radiation and at 0.151 and 0.269 using using crystal reflected MoXn radiation. Argon gas under a Cu filtered radiation. A preliminary Fourier analysis of gauge pressure of 50 lb. per sq. in. was cooled to 90'K in a our diffraction pattern results in an atomic distribution thin-walled Pyrex glass capillary of about 1.7 mm diameter curve (4mr'p(r) vs. r) showing approximately 7 atoms at and under these conditions the argon became liquid. An 3.90A and 5 atoms at about 5.05A. A third broad peak evacuated camera of 9,53 cm radius was so constructed occurs at over 7A. This indicates that the distribution of that the film could be placed outside the vacuum, with atoms in liquid argon does not follow closely that in entrance and exit windows of aluminum. Exposures of 140 crystalline argon, since in the crystal there are 12 nearest hours were required to give patterns of satisfactory density. neighbors. Further experimental work is in progress toward Of six pictures taken, three could be used. Microphotom-' improving the experimental determination of the diffrac- etering the films showed three peaks: a very strong peak tion pattern, to give the basis for this conclusion a more at sin 8/X=0. 154, a medium peak at sin 8/) =0.280 and a critical examination. weak peak at sin 8/'A=0. 415. No evidence of another peak ' Keesom and de Smedt, Proc. Amst. Acad. 12, 1 (1923). 105 AM E RI CAN P H YSI CAL SOCI ETY 1055 2. The Difraction of X-Rays by Indium, Cadmium, Zinc, resolving power of 300. For homochromatic photometry and Chlorine in the Liquid State. * CARI. GAMERTsFEI. DER, two unequal exposures were obtained on each spectrogram University of Missouri. —The x-ray diffraction patterns of by raising or lowering the plate holder through an externally the liquid elements indium, cadmium, zinc, and chlorine controlled mechanism. The effect of light fog was com- were obtained at different temperatures, using strictly pensated. This procedure also serves as a convenient means monochromatic MoXn x-rays and a camera of 9.20 cm for obtaining the calibration curve of the plate in the radius. Atomic distribution curves were obtained in the region of the band (170—240A). The x-ray technique re- usual manner. Three diffraction. maxima were obtained sembled that of O'Bryan and Skinner. ' During an exposure for indium at 160'C and 390'C. The main peak for 160'C (1—2 hours) the surface of the target was renewed every few was at sin 8/X=0. 179 and for 390'C was at sin 8/X=0. 177. minutes by evaporation. A plot of the relative intensity of The distribution curves show a concentration of 8 atoms radiation as a function of the energy of the emitted x-ray at 3.30A for 160'C and 3.36A for 390'C; also a concentra- photons shows a more marked minimum near the band tion of 4 atoms at slightly more than 4A in each case. In head and a band width comparable to those reported the crystal there are twelve nearest neighbors at an average previously. ' 2 The present measurements give a band distance of 3.32A. Cadmium at 350'C had three diffraction width of 10.2 ev. maxima, with the main peak at sin 0/X=0. 202. The dis- ' O'Bryan and Skinner, Phys. Rev. 45, 370 (1934). 2 Siegbahn, Ergebnisse der exakten Naturwissens. 16, 104 (1937). tribution curve shows a concentration of 8 atoms at 3.06A with a secondary concentration of 4 atoms at about 4A. 5. Decrease of Skin Damage by Deflecting Secondary In the crystal there are twelve nearest neighbors at an Electrons from a Beam of One Million-Volt X-Rays. G. average distance of 3.16A. Zinc at 460'C had three diffrac- FAILLA AND EDITH H. QUIMBY, Memorial Hospital. —Pre- tion maxima the second of which, at sin 8/)I =0.228, was vious experiments in this laboratory have shown that the most intense. The distribution curve has a concentration of biological effectiveness of gamma-rays can be reduced 11 atoms at 2.94A. In the crystal there are twelve nearest considerably by removing from the beam many of the neighbors with an average distance of 2.8A. For chlorine associated secondary electrons. The thickness of tissue in the distribution curve shows that there is one nearest neigh- which this obtains is of the order of one millimeter for one bor at 2.0A. million-volt x-rays. Skin erythema results largely from * Read by title. injury to cells situated close to the surface. Accordingly it should be possible to reduce skin damage of this type by the 3. A Comparison of Liquid DiBraction Patterns Using suggested method. Tests have been made by covering with Crystal-Reflected and Filtered X-Rays. N. S. GINGRzcH rubber (entirely material of low atomic number) one-half AND R. Q. GREGG, University of Missouri. —X-ray diffrac- of the skin surface exposed to one million-volt x-rays. The tion patterns of liquids are used for the determination of skin area irradiated through rubber shows a distinct ery- the structure of liquids through the use of a theoretical thema, whereas the other half shows no reddening at all. treatment that presupposes monochromatic incident x-rays. In these tests the x-rays traversed a considerable thickness Monochromatic x-rays of sufficient purity can readily be of air between the last collirnating diaphragm and the obtained by crystal reflection, but the intensity of the patient's skin, for the purpose of scattering many of the reflected beam is so low that exposures of great length are secondary electrons out of the beam. No magnetic field required. A comparison has been made between diffraction was used. The simplicity of the method makes it readily patterns of liquid sodium at 117 C taken (1) with crystal applicable to the treatment of patients. reflected x-rays and (2) with x-rays filtered in several different ways. With a Mo target tube operated at 37 kv 0. The Auger Effect in X-Ray Line Widths. JoHN N. all filtered radiation patterns show a spurious peak at small CooPER, Cornell University. —The Auger (radiationless) angles due to continuous radiation, and they all show transition I I~Lzzz Mzv, v is believed to be responsible for larger background over the whole pattern relative to the the curious variation of the intensity of the satellites of the main peak intensity. If filtering. with double thickness of x-ray lines La& and LP2 in the range of atomic numbers Zr02 and narrow slits are used the resolution of the first 70&Z~81.