โ Scribed by J.C. Wheatley; W.J. Huiskamp; A.N. Diddens; M.J. Steenland; H.A. Tolhoek
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An experiment is described in which the circular polarization of the gamma radiation emitted by polarized 6ยฐCo nuclei was measured. The detection of the circular polarization was performed by measuring the change of the Compton scattering of the gamma radiation from magnetized iron when the direction of the polarization of the nuclei is reversed. The nuclei are polarized in single crystals of 2Ce(NO3)a.3Mg(NO3)2.24H20 containing about 110 #C 6ยฐCo, which are cooled by adiabatic demagnetization from a field of about 22000 0 and a temperature of about IยฐK. A residual field of 280 0 along the trigonal axis causes a considerable degree of polarization of the nuclei, resulting in a degree of circular polarization as high as 75% at the lowest temperature, 0.006ยฐK.
The observed fractional change in counting rate E of the scattered g a m m a radiation upon changing the direction of the polarization of the nuclei relative to the direction of magnetization of the scattering iron amounted to at most 30/0 . The effect was clearly observable to temperatures up to 0.05ยฐK. F r o m the sign of the effect it can be concluded t h a t the magnetic moment of 6ยฐCo is positive. The dependence of the effect on the temperature can be calculated theoretically starting from d a t a on the h.f.s, in the crystal. When approximating this dependence by E = a / T (in the region l I T < 60) an average experimental value aex p = 0.045 ( ยฑ 10%) and an average theoretical value atheo r -----0.0445 were found. For lower temperatures (1/T > 60) there seems to be a significant difference between the experimental and theoretical values of E, which m a y be due to uncertainties in the knowledge of the hyperfine structure.
๐ SIMILAR VOLUMES
The thbory of },-radiation from oriented nuclei was developed by C o x, T o lh o e k and d e G r o o t 1) ~) 3) 4). In these papers general formulae were developed valid for any multipole order. However, for the discussion of experimental data it is useful to have more explicit formulae in which the