I. D. Petrov

Photoionization dynamics of excited Ne, Ar, Kr and Xe atoms near threshold

A review of experimental and theoretical studies of the threshold photoionization of the heavier rare-gas atoms is presented, with particular emphasis on the autoionization resonances in the spectral region between the lowest two ionization thresholds 2P3/2 and 2P1/2, accessed from the ground or excited states. Observed trends in the positions, widths and shapes of the autoionization resonances depending on the atomic number, the principal quantum number n, the orbital angular momentum quantum number l and further quantum numbers specifying the fine- and hyperfine-structure levels are summarized and discussed in the light of ab initio and multichannel quantum defect theory calculations. The dependence of the photoionization spectra on the initially prepared neutral state are also discussed, including results on the photoionization cross sections and photoelectron angular distributions of polarized excited states. The effects of various approximations in the theoretical treatment of photoionization in these systems are analysed. The very large diversity of observed phenomena and the numerous anomalies in spectral structures associated with the threshold ionization of the rare-gas atoms can be described in terms of a limited set of interactions and dynamical processes. Examples are provided illustrating characteristic aspects of the photoionization, and sets of recommended parameters describing the energy-level structure and photoionization dynamics of the rare-gas atoms are presented which were extracted in a critical analysis of the very large body of experimental and theoretical data available on these systems in the literature.

Erratum to: Experimental and theoretical cross sections for photoionization of metastable Xe*(6s 3P2, 3P0) atoms near threshold

Using high resolution laser photoelectron spectrometry we have determined absolute cross sections σJ0J1 and the electron angular distribution parameter for one photon ionization of metastable Xe*(6s3PJ0, J0 = 2, 0) atoms to the resolved Xe+ (2PJ1, J1 = 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 ß-parameters for photoionization of Xe*(6s3PJ0, J0 = 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.

Photoionization of Kr near the 4s threshold. I. Experiment and LS coupling theory

Absolute cross sections for the transitions of the Kr atom into the 4s1 and 4p4nl states of the Kr+ ion were measured in the 4s-electron threshold region by photon-induced fluorescence spectroscopy (PIFS). The cross sections for the transitions of the Kr atom into the 4s1 and 4p4nl states were also calculated, as well as the 4p4nlnl doubly excited states, in the frame of LS-coupling many-body technique. The cross sections of the doubly-excited atomic states were used to illustrate the pronounced contributions of the latter to the photoionization process, evident from the measurements. The comparison of theory and experiment led to conclusions about the origin of the main features observed in the experiment.

Photoionization of Kr 4s. III. Detailed and extended measurements of the Kr 4s-electron ionization cross section

Absolute Kr 4s-electron photoionization cross sections as a function of the exciting-photon energy were measured by photon-induced fluorescence spectroscopy (PIFS) at improved primary-energy resolution. The cross sections were determined from threshold to 33.5 eV and to 90 eV with primary-photon bandwidths of 25 meV and 50 meV, respectively. The measurements were compared with experimental data and selected theoretical calculations for the direct Kr 4s-electron photoionization cross sections.

Interaction between resonances through autoionization continua near the 4s-threshold in KrII

The interaction between resonances through autoionization continua and the interaction between autoionization continua were investigated theoretically and experimentally for the photoionization process of the 4p- and 4s-shells and for the population of 4p4 (3P)5s 4PJ, 4p4 (3P)5s 2PJ and 4p4(3P)4d 4DJ satellites of KrII. Cross sections for the satellite production and the angular distribution parameter of the fluorescence radiation were measured by photon-induced fluorescence spectroscopy after excitationx with linearly polarized monochromatized synchrotron radiation at exciting-photon energies between 28.45 eV and 29.95 eV with an exciting-photon energy resolution of 10 meV (FWHM). Measured cross sections are in good agreement with the computed ones. A refined assignment of resonances in the proximity of the 4s14p65p resonance was performed. It was concluded that there is a strong influence of the core rearrangement, of the interaction between resonances through the autoionization continua and of the interaction between autoionization continua, on the investigated processes on the basis of the observed good overall agreement between the computed and measured quantities.

Experimental and theoretical cross sections for photoionization of metastable and atoms near threshold

Using high resolution laser photoelectron spectrometry we have determined absolute cross sections σJ 0 J 1 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 s-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.

Experimental and theoretical cross sections for photoionization of metastable atoms near threshold

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. .

Photoionization of excited Ne*(2p5 3p, J = 3) atoms near threshold

Using the configuration interaction Pauli?Fock with core polarization (CIPFCP) method, we have calculated the total and the partial cross sections for photoionization of excited Ne*(2p5 3p, J = 3) atoms over the photoelectron energy range 0?2.5 eV. The total cross section exhibits nearly the same energy dependence as that for photoionization of excited Na*(3p) atoms, but the absolute size for the former is about 10% smaller. In both cases, some experimental cross sections show unexplained deviations from the theoretical predictions. Between the two ionization thresholds Ne+(2p53/2) and Ne+(2p51/2), the cross sections are predicted to be strongly influenced?albeit over only narrow intervals?by the nd(J = 2, 3) and ng(J = 3, 4) resonance series. Partial cross sections for the J = 2, 3, 4 channels and a parametrization of the resonances by Fano?Cooper-type profiles are presented. The partial cross section for leaving the Ne+ ion in the 2P1/2 level amounts to only about 0.03% near threshold, in agreement with the findings of a laser photoelectron spectrometry experiment.

Theoretical study of the Ar-3s electron photoionization and satellite production close to threshold including doubly excited states

Abstract Cross sections for photoionization of Ar-3s electrons and for satellite production were calculated near their thresholds. Moreover, energies of doubly-excited states in neutral Ar and cross sections for their population were calculated, supporting the explanation of resonance phenomena observed earlier in the 3s-electron photoionization process and in the satellite production by autoionization of doubly-excited states.

Autoionization dynamics of even Ar (3p51/2np′, nf′) resonances: comparison of experiment and theory

The 3p51/2npJ = 0, 1, 2 and 3p51/2nfJ = 2 autoionizing Rydberg states of Ar have been studied by two-step two-color photoionization of ground-state argon atoms via the intermediate levels 3p51/24s[1/2]1, 3p53/25s[3/2]1 and 3p53/23d[1/2]1, followed by time-of-flight ion detection. Accurate energy positions and widths have been determined for the 15p[1/2]0, 15p[3/2]2 and 13f[5/2]2 resonances. The measured spectra and earlier results obtained for the intermediate levels 5s[1/2]1,7s[1/2]1, and 8s[3/2]1 are compared with absolute cross sections, calculated with the configuration interaction Pauli–Fock core-polarization method.