Angular distribution of photoelectrons generated in atomic ionization by twisted radiation

Until recently, theoretical and experimental studies of photoelectron angular distributions (PADs) including non-dipole effects in atomic photo\-ionization have been performed mainly for the conventional plane-wave radiation. One can expect, however, that the non-dipole contributions to the angular- and polarization-resolved photo\-ionization 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 to 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 photo\-ionization in the region of the lowest dipole $2s2p\,[{^1P}_1]$ and quadrupole $2p^2\,[{^1D}_2]$ autoionization resonances. A noticeable variation of the PAD caused by changing the parameters of the twisted light is predicted.