Dependence of the TDPAC spectra on teh orientation of the principal axis system of the electric field gradient

Abstract

Analytical expressions are derived, which give the frequency amplitudes of a time differential perturbed angular correlation pattern, as a function of the orientation angles of the principal axis system of the electric field gradient tensor. We show, that allowed β-γ TDPAC experiments are anisotropic only if the main axis of the electric field gradient forms a unique angle with the crystal symmetry axis or if the multiple crystallographically equivalent directions in a cubic crystal are unequally populated.