Measurement of angular distribution and polarization of photon-induced fluorescent x rays in thorium and uranium

Abstract

The angular distribution and polarization of the L-shell fluorescent x rays excited by 59.57-keV photons in Th and U have been measured. It is found that the L\ensuremath{\gamma} group of L x rays is isotropic in spatial distribution and unpolarized but, the Ll and L\ensuremath{\alpha} groups are anisotropically distributed and are polarized. Although no anisotropy of the L\ensuremath{\beta} group is detected, it is found to be slightly polarized. The present results contradict the predictions of the calculations of Cooper and Zare [Atomic Collision Processes (Gordon and Breach, New York, 1969)] that after photoionization the magnetic substates of all subshell vacancy states are equally populated. However, the present results confirm the predictions of Fl\"ugge, Mehlhorn, and Schmidt [Phys. Rev. Lett. 29, 7 (1972)] that the population distribution of the magnetic substates of all subshell vacancy states with j>1/2 is nonstatistical.