EXPERIMENTAL AND THEORETICAL CROSS-SECTIONS FOR PHOTOIONIZATION OF METASTABLE XE-ASTERISK (6S P-3(2), P-3(0)) ATOMS NEAR-THRESHOLD

Using high resolution laser photoelectron spectrometry we have determi ned absolute cross sections sigma(J0J1) and the electron angular distr ibution parameter for one photon ionization of metastable Xe(Gs P-3(J 0), J(0) = 2, 0) atoms to the resolved Xe+(P-2(J1), J(1) = 3/2, 1/2) i on states at several wavelengths near threshold. For comparison with t he present and future experimental data we have calculated partial cro ss sections and P-parameters for photoionization of Xe(6s P-3(J0), J( 0) = 2,0) and of the analogous alkali atom Cs(6s) over the photoelectr on energy range (0-5) eV. We have used both a term-dependent Pauli-Foc k (PF) approach and a configuration interaction method involving Pauli -Fock atomic orbitals (CIPF). Through the PF method we include relativ istic effects on the atomic orbitals; the CIPF method was designed to take into account the important electron correlation effects which are found to be essential for obtaining good agreement between the theore tical and experimental results.