Relativistic calculation of the angular dependence of nondipole photoemission time delay*

It has recently been shown that, owing to their different parities, dipole and quadrupole photoionizing transitions behave differently as functions of angle, thereby allowing for the possibility of retrieval of the quadrupole contribution to attosecond time delay in photoemission experimentally [1].  In order to pave the way for such studies, we have embarked on a program to study the dependence of Wigner time delay for quadrupole time delay for photoemission from the various subshells of the noble gas atoms, Ne, Ar, Kr and Xe.  Calculations at the level of the relativistic-random-phase approximation (RRPA) that has been upgraded to handle quadrupole interactions have been initiated.  The studies will provide information on the attosecond dynamics of ionizing quadrupole transitions.  Recent results for Ar ns and np subshells will be presented. Similar calculations will be extended to the other noble gas atoms, as well as various other atomic systems. [1] M. Ya. Amusia and L. V. Chernysheva, JETP Lett. 112, 673 (2020).