Time-of-Flight Measurements of Cesium-Iodide Cluster Ions

Secondary ions [(CsI)ₙCs]⁺, with n up to {~} 40, were produced by 8-keV Cs⁺ bombardment of CsI. The yield of clusters decreased smoothly with n when observed in a time-of-flight mass spectrometer at effective times {~} 0.2 {μ}s after emission. Clusters with $n>7$ were found to be metastable, with lifetimes {} 100 {μ}s. A large anomaly in the population of the disintegration products was measured at {~} 70 {μ}s after emission, $n=13$ clusters being favored and n=14 and 15 suppressed.