Multiple K-shell excitation of lithium clusters: Implications for hollow-atom solids

Abstract

Systematic molecular-orbital calculations are performed for Li9z+ clusters in which Nexc (= 0-9) core electrons are excited to valence orbitals. For neutral (z=0) clusters, the magnitudes of work functions, cohesive energies, and average core-electron excitation energies increase with Nexc, owing to relaxation of valence electrons around localized core holes. Total energy of a multiply charge ion, produced by a series of Auger decay, remains lower than the corresponding dissociation limit as far as z≦3. We thereby discuss a possibility of realizing a hollow-atom solid, multiply core-excited state with temporal crystalline order, by utilizing intense free-electron lasers.