Contains reports on five research projects.United States Atomic Energy Commission (Contract AT(30-1)-1283

Adams, N. I., III

Bitter, F.

Davis, S. P.

Lubell, M. S.

Murray, G. R., Jr.

Plotkin, H. H.

Richter, B.

Sagalyn, P. L.

Waugh, J. S.

Young, J. E. R.

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VI. MAGNET LABORATORY RESEARCHProf. F. Bitter ,,Dr. S. P. DavisDr. P. L. SagalynDr. J. S. WaughN. I. Adams IIIM. S. LubellG. R. Murray, Jr.H. H. PlotkinB. RichterJ. R. StanleyJ. E. R. YoungA. MAGNETO-OPTIC STUDIES OF Hg196 AND Hg 1 9 7By previously described methods we have repeated observations on radioactivemercury prepared by bombarding gold with 15-Mev deuterons. Five new hyperfinestructure lines have been observed, of which three have been identified with reasonable196certainty. One of these is attributable to Hg , a stable isotope present to only 0.15 per-cent in natural mercury but much more abundant in the residues of the samples obtainedfrom bombarded gold. The lines from even-even isotopes are readily identified by thefact that their Zeeman effect consists of a normal triplet whose center, or Tr-component,is undisplaced. The isotope shifts are compared in Fig. VI-1.Two other lines have been identified from their g-factors as having F = 3/2 and 1/2.197Since such lines would be expected for Hg , which is predicted and observed (1) tohave a spin of 1/2, and since these lines disappeared at a rate, if not measurable, at204 202 200 198 196PRESENT I7+OBSERVATIONS 0.172 0171 0.157 0.136PREVIOUS 0.175 0.179 0.168OBSERVATIONS k I+ +0.1850.1750.1650.1550.1450.135PREVIOUS OBSERVATIONS:RVATIONS198TO196Fig. VI-1Frequency separation or A.53b components in cm-26-Spectroscopy Laboratory, M. I. T.Fig VI^'"er-:RVATIONSi---I(VI. MAGNET LABORATORY RESEARCH)197least not inconsistent with the 64-hour half-life of Hg , we have tentatively assigned197these to the ground state of Hg This leads to a magnetic moment for this isotopeequal to that of Hg19 9 within a few percent, and to an isotope shift for the center of199 197gravity of Hg to Hg slightly smaller than the 198 to 196 shift shown in Fig. VI-1.F. Bitter, H. H. Plotkin, B. Richter, J. E. R. YoungReferences1. O. Huber, F. Humbel, H. Schneider, A. deShalit, and W. Zunti, Helv. Phys.Acta 24, 127 (1951).B. NUCLEAR MAGNETIC RESONANCE IN GASESIn molecular gases, the width of the resonance is inversely proportional to the aver-age frequency with which the molecule is reoriented. This is the kinetic collisionfrequency. Many gases are vapors at room temperature (that is, have a maximumpressure); thus they have a minimum linewidth. However, if we add other gases, thecollision frequency may be increased, and the linewidth be reduced below the value setby vapor pressure. The purpose of the present measurements is to evaluate the effec-tiveness of various added gases and to compare this with estimates from kinetic theory.N. I. Adams IIIC. THE SELF-REVERSAL OF Na RESONANCE RADIATIONThe question of self-reversal in the light source is of interest in connection with therecent work on sodium (1). The source used was an ordinary sodium laboratory arc.Since the lines from this arc are known to beself-reversed, a high-frequency dischargetube containing sodium metal was constructed.Spectrograms of the D line at 5890A areshown in Fig. VI-2. They were taken on aSpectroscopy Laboratory echelle, with a platefactor of approximately 0. 5 A/mm. Varyingintensity along the lines was produced by astep sector at the slit that had steps withexposure-time ratios of 2:1. The power input(a) (b) to the high-frequency exciting source, a QK-61magnetron, was 25 watts. Note that theFig. VI-2 laboratory arc shows a reversal width ofSpectrograms of the D line ofNa at 5890A: (a) laboratory arc; approximately 0. 7A, while the discharge tube(b) high-frequency discharge. shows very little, if any. When operated at-27-(VI. MAGNET LABORATORY RESEARCH)twice the input power and with external heating, however, the tube showed nearly asmuch reversal as the arc. More quantitative measurements than these have not beenmade.S. P. Davis, P. L. SagalynReferences1. P. L. Sagalyn, Doctoral Thesis, Department of Physics, M. I. T. (1952) (Phys. Rev.article in press).D. THE ZEEMAN EFFECT OF MERCURY (X = 4047A)Further work (1) on obtaining the emission spectrum of small amounts of mercuryindicates that the 4047A line (3P - 3S1) furnishes desired information concerning thesplitting of the upper level. Spectrograms taken on the Spectroscopy Laboratory echelleshow clearly separated hfs components, and it has proved possible to follow their(0)(b)Fig. VI-3Spectrograms of mercury at 4047A: (a) The centralbright component is due to the even isotopes. Theouter faint components are the hfs lines of the iso-topes with an odd number of neutrons (zero field).(b) The three bright lines are the normal Zeemantriplet produced by the even isotopes. The splittingof the hyperfine structure is complicated (B = 14, 000gauss).Part of this work was supported by AEC Contract AT(30-1)-1283.-28-(VI. MAGNET LABORATORY RESEARCH)splittings in magnetic fields up to approximately 14, 000 gauss. These components andsplittings are shown in Fig. VI-3.S. P. DavisReferences1. Quarterly Progress Report, Research Laboratory of Electronics, M. I. T., July 15,1953, p. 32.E. NUCLEAR RESONANCE STUDIES OF SOLIDS AND LIQUIDSThe interactions of nuclear multipole moments with their surroundings, occurringas perturbations on a strong coupling of the magnetic dipole moment with an externalmagnetic field, can be used as a means of studying the nuclear environment. Thedesired information is contained in the breadth and fine structure of radiofrequencyresonance absorption lines in bulk matter. The work of this project can conveniently bedivided into two parts.1. The temperature dependence of splittings caused by nuclear dipole-dipole couplingin crystals will be investigated as a means of studying the conditions necessary for large-scale motions and polymorphic phase transitions. Closely related series of compoundsamong the ammonium halides, alkali borohydrides, and octohedral coordination com-plexes of cobalt, and the like, will be investigated to elucidate these matters, includingthe role of cooperative phenomena in phase transitions and the coupling of lattice dis-turbances with molecular activation leading to initiation of chemical reaction. Thevariable frequency regenerative spectrometer with homodyne detection to be used forthese experiments has been largely assembled.2. Studies will be made of electron distributions in molecules by the measurementof diamagnetic shifts in the Larmor frequency and of electron-coupled nuclear inter-actions. The general aim of this work is the correlation of these spectra with molecularstructure, properties, and mode of chemical reactivity. Since extremely high resolutionis required, studies are being made of the factors governing the homogeneity of magneticfields. It is hoped that by means of special magnet design and flowing-sample techniquesit will be possible to produce fields of very high effective local uniformity with consid-erably less labor and expense than have heretofore appeared necessary. A fixed-frequency spectrometer of the bridge type will be used under slow passage conditions.J. S. Waugh, G. R. Murray, Jr., M. S. Lubell-29-

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