We identified interatomic Coulombic decay (ICD) channels in argon dimers after spectator-type resonant Auger decay $2p^{-1}~3d to 3p^{-2}3d, 4d$ in one of the atoms, using momentum resolved electron-ion-ion coincidence. The results illustrate that th
e resonant core excitation is a very efficient way of producing slow electrons at a specific site, which may cause localized radiation damage. We find also that ICD rate for $3p^{-2}4d$ is significantly lower than that for $3p^{-2}3d$.
We have investigated multiphoton multiple ionization dynamics of argon and xenon atoms using a new x-ray free electron laser (XFEL) facility, SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan, and identified that highly charged Xe ions w
ith the charge state up to +26 are produced predominantly via four-photon absorption as well as highly charged Ar ions with the charge state up to +10 are produced via two-photon absorption at a photon energy of 5.5 keV. The absolute fluence of the XFEL pulse, needed for comparison between theory and experiment, has been determined using two-photon processes in the argon atom with the help of benchmark ab initio calculations. Our experimental results, in combination with a newly developed theoretical model for heavy atoms, demonstrate the occurrence of multiphoton absorption involving deep inner shells.
