Electronic decay of valence holes in clusters and condensed matter

Following innervalence ionization of a cluster, the system can relax by electron emission, a phenomenon called intermolecular Coulombic decay. This process is characterized by an efficient energy transfer mechanism between neighboring monomers in the cluster. A theoretical description within the framework of Wigner-Weisskopf theory is developed, thus enabling a detailed analysis of the decay process. The main result of the formal treatment, a simple, approximate expression for the electronic decay width of an innervalence hole state, is applied to investigate the effect of cluster size. On the basis of extensive ab initio calculations, pronounced size effects are found in the concrete example of neon clusters. The decay lifetime decreases in a monotonic fashion from hundred femtoseconds in Ne₂ down to less than ten femtoseconds in Ne₁₃. Suggestions are made how to facilitate the experimental observation of intermolecular Coulombic decay in clusters and condensed matter.