Angular anisotropy parameters for photoionization delays

Anisotropy parameters describing the angular dependence of photoionization delay are defined. The formalism is applied to results obtained with relativistic random phase approximation exchange for from outermost $s$-orbitals in selected rare-gas atoms. Any Wigner induced here by effects, while measurable atomic exhibits such a also nonrelativistic limit. contributions anisotropy different sources disentangled and discussed. For heavier rare gases, it shown that measurements electrons ejected specific angles, relative to, e.g., those along laser polarization, directly related delay. considerable range second photon largely get canceled when angles compared, this angle-relative then close corresponding