Direct double ionization of the Ar+ M shell by a single photon

Abstract

Direct double ionization of the Ar + (3p −1 ) ion by a single photon is investigated both experimentally and theoretically. The photon-ion merged-beams technique was employed at the Advanced Light Source in Berkeley, USA, to measure absolute cross sections in the energy range from 60 to 150 eV. In this range, three contributions to the double ionization of Ar + are to be expected: the removal of two 3p electrons, of a 3s and a 3p electron, and of two 3s electrons. Among the possible mechanisms leading to double ionization, the TS1 (two-step one) process dominates in the near-threshold region. In TS1, a photoelectron is ejected and, on its way out, knocks out a secondary electron. This two-step mechanism is treated theoretically by multiplying the calculated cross section for direct single photoionization of a given subshell with the calculated (e, 2e) ionization probability for the ejected photoelectron to knock off a secondary electron. The calculated cross section is in very good agreement with the experiment.

Pulse length effects in long wavelength driven non-sequential double ionization

“…Ubiquitous in many strong-field phenomena, electron correlations during atomical multi-electron ionization play an instrumental role and have been widely investigated. Even the direct single-photon double ionization (DI), in which the electron-electron interaction happens either before (shake off) or after (knock out) the photon absorption takes place, carries rich physical information [4,5]. If the electron emitted after single ionization is driven back to the nucleus by the intense laser field, the inelastic scattering dynamics will be induced by the recollision, and non-sequential DI (NSDI) may occur.…”