Production and properties of singly and multiply charged Kr clusters

Abstract

Kr clusters produced in a supersonic nozzle expansion have been studied by electron impact ionizationmass spectrometry. Mass resolved spectra (with n up to 180) show two homologous series consisting of Kr+ n and Kr2+ n ions. The distribution of Kr+ n ions shows distinct magic number effects, the observed abundance anomalies being very similar to the ones observed in Ar and Xe. This confirms the superior stability of closed‐shell and ‐subshell icosahedral structures. Moreover, we have found evidence for the occurrence of Kr3+ n and Kr4+ n ions. It was possible to determine appearance sizes of these multiply charged cluster ions (yielding n 2=69, n 3=156, and n 4=264), and to study the electron energy dependence of singly and doubly charged cluster ions (yielding a linear threshold law). These results are discussed in view of various theoretical considerations and previous results where available.