Photofragmentation Patterns of Cobalt Oxide Cations Co_nO_m⁺ (n = 5–9, m = 4–13): From Oxygen-Deficient to Oxygen-Rich Species

Abstract

Cobalt oxide clusters, Co n O + m (5 ≤ n ≤ 9 and 4 ≤ m ≤ 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 m = n-1, m = n-2, and m ≥ n species are investigated. Loss of oxygen molecules is the favorable dissociation channel of m ≥ n clusters. While Co n O + n−2 clusters decay via the separation of a Co atom, the photofragmentation behavior of Co n O + n−1 species interestingly can be divided into two regimes: the n ≤ 1 6 clusters tend to lose an oxygen atom, but for n > 6 they favorably dissociate via the loss of a cobalt atom. The geometric structures of selected m = n−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.

Influence of oxidation on the magnetism of small Co oxide clusters probed by Stern–Gerlach deflection

“…The strong interaction between cobalt and oxygen, also known from previous studies, 15 shows up in different properties of the clusters. First, the lowest energy structures of all calculated clusters (presented in Fig.…”

“…12,13 This is also the case for cobalt oxide clusters which have been the subject of several theoretical and experimental studies examining various properties. Experimentally, efforts were undertaken to investigate them by means of photofragmentation, 14,15 photoelectron spectroscopy, 16 and infrared vibrational spectroscopy. 17 Also the role of cobalt oxide clusters as catalysts 18 and their reaction with different gases 19 have been studied.…”