Contains reports on three research projects

Davis, C. F., Jr.

Solt, I. H., Jr.

Tinkham, M.

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V. MICROWAVE SPECTROSCOPYProf. M. W. P. Strandberg B. Josephson, Jr. M. U. PalmaDr. D. Kivelson J. D. Kierstead M. PeterC. F. Davis, Jr. H. Kleiman I. H. Solt, Jr.H. Dreicer S. Krongelb W. ThompsonJ. G. Ingersoll Maria B. Palma M. TinkhamA. MICROWAVE SPECTRUM OF OXYGENIn the Quarterly Progress Report of April 15, 1954, we summarized the many quan-titative conclusions we have been able to reach from the energy levels and spectrum ofthe oxygen molecule. On the subject of linebreadths and intermolecular interactions wehave less definite conclusions to offer. We can say, however, that the striking depend-ence of the linebreadth on all quantum numbers reported by Beringer and Castle (1) wasthe result of improper theoretical interpretation of their experimental data. With thelines which they observed identified by our work, and with the widths correctly inter-preted, their work is in fair agreement with ours. Our results show a slight decreasein width with increasing K but no significant M dependence. The temperature depend--nence is as T -n , where n = 0. 75 + 0. 04. This indicates a "softer" interaction than thatof hard spheres (n = 0. 5) or the combination of exchange and polarizability interactionsconsidered by Artman (n = 0. 627). A quadrupole-quadrupole interaction would given = 0. 75, but it seems likely that other interactions are more important. A review ofthese interactions, especially as they affect the nondegenerate states produced by theZeeman splitting, would be a worthwhile extension of the work reported here.Our final linebreadth result is that air broadening is as effective or slightly moreeffective than pure 0 2 self-broadening. This indicates that for the nondegenerate levelsthat concern us, the O2-N 2 collision cross section equals or exceeds the 02-OZ crosssection. This is contrary to the results of previous investigators on the field-freespectrum, which indicated that 0 O2-N Z  0.85 O 2-0 . This discrepancy is explainedby the assumption that rotational resonance interactions make an appreciable contri-bution to the 02 self-broadening in the field-free case.M. TinkhamReferences1. R. Beringer and J. G. Castle, Jr., Phys. Rev. 81, 82 (1951).B. CONDUCTION ELECTRON RESONANCE IN METALSIn the Quarterly Progress Report of January 15, 1954, results were given on themagnetic resonance absorption of metallic sodium at 9000 Mc/sec. This included dataon the line shape, linewidth, and g-values at 3000K, 780K, and 4 0 K. Since then metallic28-(V. MICROWAVE SPECTROSCOPY)lithium and potassium have been investigated. As in sodium, colloidal suspensionsof lithium and potassium were made by ultrasonically dispersing the metals in paraffinwax.For lithium,-an asymmetric line shape similar to that of sodium was observed, theline shape being proportional to the sum of the real and imaginary parts of the suscep-tibility. The linewidth (corresponding to the full width at the half-power points of theimaginary part of the susceptibility) differed from sodium in that it was essentiallytemperature-independent. Its value is approximately 2.7 gauss. The observed g-valuesare g = 2. 0024 + 0. 0001 at 300 0 K, and g = 2. 0022 + 0. 0001 at 78°K and 4°K.For potassium the linewidth was considerably broader and was temperature-dependent. At 300 0K it was 254 gauss; at 78°K, 90 gauss; and at 4°K, 32.7 gauss. Ihave so far been unable to get any accurate measurements of the g-value. At 300 0 K and78°K the linewidth is too broad. However, it is hoped that at 4°K sufficient accuracycan be obtained with the narrow line.With these g-value measurements and temperature dependences of the linewidths,one can then establish whether the latter phenomenon is due to spin-orbit interactionsas believed. If so, there should exist a definite relation between them. The data forsodium and lithium agree quite well with these assumptions.I. H. Solt, Jr.C. A PARAMAGNETIC RESONANCE STUDY OF AMMONIUM CHROME ALUMAdditional experimental, theoretical, and calculational work has been done on theline position and intensity of the paramagnetic resonance spectrum of single crystals ofammonium chrome alum. Line positions are calculable from theory to approximately0. 2 percent; relative line intensities to approximately 10 percent (1). The line shapeseems to be quite lorentzian for the dilute materials, 1:15, 1:60, and gaussian forstraight alum. Linewidth varies characteristically from one line to another; the centerabsorption is approximately 25 percent narrower than the extremes.C. F. Davis, Jr.References1. C. F. Davis, Jr. and M. W. P. Strandberg, American Physical Society Meeting,Washington, D. C., April 29, 1954.-29-

Microwave Spectroscopy

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Microwave Spectroscopy

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