Angular distribution of photoelectrons generated in atomic ionization by twisted radiation

Until recently, theoretical and experimental studies of photoelectron angular distributions (PADs) including nondipole effects in atomic photoionization have been performed mainly for the conventional plane-wave radiation. One can expect, however, that the nondipole contributions to the angular-and polarization-resolved photoionization properties are enhanced if an atomic target is exposed to twisted light. The purpose of the present study is to develop a theory for PADs for the case of twisted light, especially for many-electron atoms. The theoretical analysis is performed for the experimentally relevant case of macroscopic atomic targets, i.e., when the cross-sectional area of the target is larger than the characteristic transversal size of the twisted beam. For such a scenario, we derive expressions for the angular distribution of the emitted photoelectrons under the influence of twisted Bessel beams. As an illustrative example, we consider helium photoionization in the region of the lowest dipole 2s2p [1P1] and quadrupole 2p2 [1D2] autoionization resonances. A noticeable variation of the PAD caused by changing the parameters of the twisted light is predicted.