Photofragmentation Patterns of Cobalt Oxide Cations CoO ( = 5-9, = 4-13): From Oxygen-Deficient to Oxygen-Rich Species.

Cobalt oxide clusters, CoO (5 ≤ ≤ 9 and 4 ≤ ≤ 13), are produced by laser vaporization and studied by time-of-flight mass spectrometry. Specific stoichiometries are mass separated and photofragmented using 355 nm laser light. The preferred fragmentation channels of = -1, = -2, and ≥ species are investigated. Loss of oxygen molecules is the favorable dissociation channel of ≥ clusters. While CoO clusters decay via the loss of a Co atom, the photofragmentation behavior of CoO species interestingly can be divided into two regimes: the ≤ 6 clusters tend to lose an oxygen atom, but for > 6 they favorably dissociate via the loss of a cobalt atom. The geometric structures of selected = - 2 species are studied using density functional theory calculations. Dissociation energies for different evaporation channels are calculated and thermodynamically favorable channels are found to correspond to the experimental observations.