ANGULAR-CORRELATION OF GAMMA-E CASCADES IN THE PRESENCE OF HYPERFINE SPLITTING OF NUCLEAR-LEVELS AND ITS POSSIBLE INFLUENCE ON CEM SPECTRA

The anisotropy of conversion electron emission in transitions between separate magnetic sublevels and its effects on energy and angular reso lved conversion electron Mossbauer spectra (CEMS) is treated theoretic ally. The angular dependence of the separate lines in a CEM spectrum i s expressed through the ''particle parameters'' b(k) which enter in th e expansion in Legendre polynomials P-k(cos Theta). The values of b(k) were obtained from the tables of Hager and Seltzer (Hager, R. S. and Seltzer, E. C., Nucl. Data A4, 397 (1968)) by extrapolation. For the M 1 transition in Fe-57 the value of b(k) was not found in the literatur e and new calculations were done which gave b(k) = + 0.017. It turns o ut that for low energy Mossbauer transitions of M1 character (Fe-57, S n-119, Te-125, Tm-169) the angular distribution of the conversion elec tron emission is almost isotropic (b(k) similar to 0.01 - 0.06) and re lative line intensities in CEM spectra differ from those in the absorp tion spectrum by no more than to 2-5%. For EL transitions this angular distribution is strongly anisotropic, so the shape of the magneticall y split CEM spectrum depends on the angle of electron emission. The co nsidered effect could be observed for electrons emitted from small dep ths and it should be taken into account if correct information about t hin layer magnetism is to be obtained from CEMS.