Angular distributions of photoelectrons from polarized atoms near threshold: experimental results and theoretical analysis

Abstract

Following our recent mass spectrometric study of wavelength-dependent photoionization of laser-excited, polarized atoms near threshold (1997 30 609) we report electron angular distributions for photoionization of polarized atoms at four energies above the threshold. The measurements allow us to both check the atomic alignment produced in the optical pumping process and test in detail results of theoretical many-electron calculations for the relevant reduced dipole matrix elements and phase shifts. In contrast to the situation for (1983 16 2945), photoionization of cannot be simply described by two reduced matrix elements and and a single phase difference . For the term dependence of the Hartree-Fock wavefunctions and correlation effects lead to substantial differences between the reduced matrix elements for the five d-wave channels and between the five existing phase differences. The comparison of the experimental angular distributions with those calculated theoretically shows that good agreement is obtained when the theoretical values of the reduced matrix elements for the d-wave channels are increased (relative to that for the s-wave channel) by a common, energy-dependent factor; this finding is in accord with conclusions from the polarization-dependent ion production data. The correction factors range from 1.4 to 1.1 -846 meV) for calculations which include long-range core polarization effects, while they amount to values between 2.0 and 1.5 when core polarization effects are neglected.