Enhanced nondipole effects in photoelectron angular distributions near giant dipole autoionizing resonances in atoms

Abstract

It is found that dipole-quadrupole photoelectron angular distribution parameters in regions of $n\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{nd}$ giant dipole resonances in $3d(n=3)$ and $4d(n=4)$ transition-metal atoms are resonantly increased to such an extent that they can dominate the effects of dipole transitions on the asymmetry of the photoelectron angular distribution. This is illustrated for $3d$ photoionization of Cr and Mn, as well as for $4d$ photoionization of Mo and Tc, where the ``spin-polarized'' random-phase approximation with exchange calculations are performed with allowance for correlations in both dipole and quadrupole channels.