Two-photon excitation-ionization of the 1s shell of highly charged positive atomic ions

Abstract

The non-relativistic absolute values and shapes of the cross sections for the process of two-photon one-electron excitation-ionization of the 1s shell of highly charged positive atomic ions Ne6+ and Ne8+ are calculated using second-order quantum-mechanical perturbation theory, taking into account the many-particle effect of relaxation of the ion residue in the field of the virtual vacancies created. The many-particle effect of stabilization of the deep vacancy when changing target from the neutral atom to the highly charged positive ions is also taken into account. The calculations are fulfilled for both linearly and circularly polarized incident photons.

Enhanced nonlinear response of Ne8+to intense ultrafast x rays

“…The Ne 9+ /Ne 8+ ratio was observed to depend quadratically on the peak intensity, which is consistent with nonlinear two-photon ionization of Ne 8+ . Nevertheless, the two-photon ionization cross section, deduced from this experimental observation with the help of a rate-equation model, is 7 × 10 −54 cm 4 s, which is two orders of magnitude higher than the value obtained within perturbation theory [11,12].…”

“…For the latter, we use the HFS model [29], implemented within the XATOM code [30,31] LOPT (ω) such that the 1s 2 -1s4p resonance is at the right position of 1127.1 eV. Doumy et al [6] noticed that in a similar perturbative calculation [11] the authors did not account for the 1s 2 -1s4p resonance. We have included this resonance in both TDCIS and LOPT calculations.…”

“…In the case of a finite-bandwidth field and near an intermediate resonance of the target atom the two-photon ionization cross section for an incoherent pulse can be cast in the form (8) where F (ω,ω in , ω p ) is the normalized spectral distribution function and σ (2) LOPT is the result of the LOPT for monochromatic radiation [11,12,36]:…”

“…In the present paper, we focus on the following points: (i) the discrepancy between the observed [6] and theoretically predicted [11] two-photon ionization cross-section values of Ne 8+ and (ii) the possibility of two-photon ionization of a 1s electron in neutral neon below the K-shell threshold of neon.…”

Nonsequential two-photon absorption from the K shell in solid zirconium

“…The results were found to be 2-3 orders of magnitude higher than both the nonresonant perturbative scaling of Ref. [11] and the second-order perturbation theory calculations of Novikov and Hopersky [13], and were attributed to contributions from near-resonant states [14].…”