Using high resolution laser photoelectron spectrometry we have determined absolute cross sections σ J0J1 and the electron angular distribution parameter for one photon ionization of metastable Xe * (6s 3 P J0 , J 0 = 2, 0) atoms to the resolved Xe + ( 2 P J1 , J 1 = 3/2, 1/2) ion states at several wavelengths near threshold. For comparison with the present and future experimental data we have calculated partial cross sections and β-parameters for photoionization of Xe * (6s 3 P J0 , J 0 = 2, 0) and of the analogous alkali atom Cs(6s) over the photoelectron energy range (0-5) eV. We have used both a term-dependent Pauli-Fock (PF) approach and a configuration interaction method involving Pauli-Fock atomic orbitals (CIPF). Through the PF method we include relativistic 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 theoretical and experimental results.

Using high-resolution laser photoelectron spectrometry we have determined for the first time absolute cross sections and the electron angular distribution parameter for one-photon ionization of metastable atoms to the resolved ion states near threshold as well as the -parameter for metastable atoms at , 257.25 nm. For comparison with present and future experimental data we have calculated partial cross sections and -parameters for photoionization of , and of the analogous alkali atom over the photoelectron energy range 0 - 10 eV. We have used both a term-dependent Hartree - Fock approach and a configuration-interaction method involving Pauli - Fock atomic orbitals (CIPF); the latter was designed to take into account the important electron correlation effects which are found to be essential for obtaining good agreement between the theoretical and experimental results. .

Using a crossed atomic and laser beams set-up with mass spectrometric ion detection we have studied the photoionization of laser-excited, aligned Ar * (3p 5 4p 3 D 3 ) atoms from the Ar + ( 2 P 3/2 ) threshold up to photoelectron energies of ε = 0.846 eV. Absolute cross sections are reported for parallel (η = 0 • ) and perpendicular (η = 90 • ) polarization directions of the linearly polarized exciting and ionizing CW lasers over the range ε = 0-0.2 eV. The cross sections exhibit nd (J = 2, 3) autoionization resonances whose combined appearance varies with angle η; this behaviour is traced to the η dependence of the partial cross sections for the final (ion + electron) channels with different total angular momentum, J 1 . Using theoretical formulae whose derivation is outlined we determine the energy dependence of these partial cross sections from least squares fits to the data measured at η = 0 • and 90 • . Experimental results are also presented for the asymmetry function, A LD (η), which describes the linear dichroism for the photoionization of aligned Ar * (4p 3 D 3 ) atoms, and for the full η dependence of the ionization cross section as obtained for 10 selected photoelectron energies in the range (0.017-0.846) eV. Many-electron calculations have been carried out which provide additional insight into the photoionization dynamics. In contrast to the situation for Ne * (3p, J = 3), photoionization of Ar * (4p, J = 3) is not well described by just two reduced matrix elements D s , D d . For Ar * 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 associated with the Ar + ( 2 P 3/2 ) formation. Satisfactory overall agreement is observed between the experimental and theoretical cross sections and their polarization dependence. The calculations also provide information on the weak g-wave contributions and on the cross section for leaving the ion in the excited Ar + ( 2 P 1/2 ) level; the latter amounts to about 1% relative to Ar + ( 2 P 3/2 ) formation in agreement with experimental and MQDT estimates.

No abstract

Using high-resolution laser photoelectron spectrometry we have determined absolute cross sections σ J 0 J 1 and the electron angular distribution parameter β J 0 J 1 for one-photon ionization of metastable Ar * (J 0 = 0, 2) and Kr * (J 0 = 0, 2) atoms to the resolved J 1 = 3/2, 1/2 ion states near threshold (λ = 351-244 nm). For comparison with the experimental data we have carried out many-electron calculations of the relevant partial cross sections and β parameters over the photoelectron energy range (0-6 eV). We have used a configuration interaction method involving Pauli-Fock atomic orbitals (CIPF), designed to take into account the important electron correlation effects which are found to be essential for obtaining satisfactory agreement between the theoretical and experimental results. Including previously reported cross sections for metastable Ne * and Xe * atoms we present a discussion of the trends which are observed in the different energy-dependent cross sections as a function of the atomic number.