Dynamics of interatomic Coulombic decay in neon dimers by XUV-pump–XUV-probe spectroscopy

Abstract

We apply the Monte Carlo wave-packet approach to study the interatomic Coulombic decay (ICD) dynamics of neon dimers after removing a $2s$ electron from one of the Ne atoms by one-photon absorption from an XUV pulse. This method reproduces well both the lifetime for the $2s$ inner-valence vacancy in $\mathrm{Ne}{}_{2}{}^{+}(2{s}^{\ensuremath{-}1})$ and the kinetic energy release (KER) spectra for the coincident ${\mathrm{Ne}}^{+}$ and ${\mathrm{Ne}}^{2+}$ fragments following triple ionization, i.e., two photoionizations and one ionization via ICD, of ${\mathrm{Ne}}_{2}$ measured in an XUV-pump--XUV-probe experiment [K. Schnorr et al., Phys. Rev. Lett. 111, 093402 (2013)]. Comparisons between the calculated and measured nuclear KER spectra give physical insights in the considered process. For example, an analysis of the ratios between the low- and high-energy peaks in the nuclear KER spectra for large delays provides an estimate of the photoionization cross sections for removing a $2p$ electron from the excited states in $\mathrm{Ne}{}_{2}{}^{+}(2{s}^{\ensuremath{-}1})$. Such comparisons also allow an estimate for the ICD rates for the $2s$ inner-valence vacancy in the single-site two hole state in $\mathrm{Ne}{{}_{2}}^{2+}(2{s}^{\ensuremath{-}1}2{p}^{\ensuremath{-}1})$. Finally, the influence of photon statistics of the free electron laser pulses on the nuclear KER spectra is considered.