Multiply charged ions induced by multiphoton absorption in rare gases at 0.53 μm

TLDR

The study elucidates the mechanism of Xe²⁺ ion formation. Xe²⁺ ions are produced by direct 15‑photon absorption at low intensities and by a stepwise process via Xe⁺ at higher intensities, with a kinetic rate‑equation model fitting the data. Up to Xe⁴⁺ ions were produced, with distinct intensity thresholds for the two Xe²⁺ formation pathways, and first‑time multiphoton ionization cross sections for two‑electron removal from Xe and one‑electron removal from Xe⁺ were measured.

Abstract

Up to quadruply charged ions are induced in Xe atoms by a 50-psec laser pulse at 0.53 \ensuremath{\mu}m in the ${10}^{12}$ W ${\mathrm{cm}}^{\ensuremath{-}2}$ range. The mechanism of the formation of ${\mathrm{Xe}}^{2+}$ ions is elucidated. In the lowest intensity range, ${\mathrm{Xe}}^{2+}$ ions are produced by direct 15-photon absorption from the ground state of the atoms, while at a higher intensity ${\mathrm{Xe}}^{2+}$ ions are produced by a stepwise process via ${\mathrm{Xe}}^{+}$ ions. These two processes take place at distinctly different intensities. A kinetic model using rate equations affords a good fit with experimental results. Moreover, for the first time it was possible to obtain the multiphoton ionization cross sections related to the two-electron removal from Xe atoms, as well as the one-electron removal from ${\mathrm{Xe}}^{+}$ ions.