Photodissociation of Cobalt and Nickel Oxide Cluster Cations

Abstract

Cobalt and nickel oxide cluster cations, Co(x)O(y)(+) and Ni(x)O(y)(+), are produced by laser vaporization of metal rods in a pulsed nozzle cluster source and detected using time-of-flight mass spectrometry. The mass spectra show prominent stoichiometries of x = y for Co(x)O(y)(+) along with x = y and x = y - 1 for Ni(x)O(y)(+). The cluster cations are mass selected and multiphoton photodissociated using the third harmonic (355 nm) of a Nd:YAG laser. Although various channels are observed, photofragmentation exhibits two main forms of dissociation processes in each system. Co(x)O(y)(+) dissociates preferentially through the loss of O(2) and the formation of cobalt oxide clusters with a 1:1 stoichiometry. The Co(4)O(4)(+) cluster seems to be particularly stable. Ni(x)O(y)(+) fragments reveal a similar loss of O(2), although they are found to favor metal-rich fragments with stoichiometries of Ni(x)O(x-1). The Ni(2)O(+) fragment is produced from many parent ions. The patterns in fragmentation here are not nearly as strong as those seen for early or mid-period transition-metal oxides studied previously.

Structural, electronic and magnetic properties of stoichiometric cobalt oxide clusters (CoO)nq (n=3−10,q=0,+1): A modified basin-hopping Monte Carlo algorithm with spin-polarized DFT

“…5 where the largest positive value of (CoO) 4 indicates its highest stability that is in agreement with the mass spectrometry observations. 2 This¯gure also displays the stability of (CoO) þ 4 agrees well with previous results, 7,8,49 whereas the (CoO) are the most unstable clusters. These results, particularly, the stability of (CoO) 4 cluster are supported by the results of Table 2.…”

“…where dissociation of (CoO) þ 5 agrees experimentally observed by Duncan et al 49 Another two potential regions leading to the formation of (CoO) 4 are…”

“…agreeing well with the second-order energy prediction. Experimental dissociation study of ðCoOÞ þ 4 by Duncan et al 49 revealed the Co 3 O þ 4 is the major product fragment. However, the current work predicts the favorable dissociation channel due the loss of one CoO molecule, giving…”

First principles study of electronic structure for cubane-like and ring-shaped structures of M4O4, M4S4 clusters (M = Mn, Fe, Co, Ni, Cu)

“…It is interesting to follow-up that several molecular beam experiments on the isolated M m O n oxide clusters of the 3d late transition metal M atoms indicate a preference for the M:O ratio as 1:1 particularly in case of the smaller cluster sizes. [16][17][18][19] Attempts of searching for the structures of the smallest building blocks in the structures of such oxide nano particles, have also been offered recently by some first principles theoretical calculations. 20,21 We will concentrate here on the structure, electronic and magnetic properties of the isolated and isoatomic M 4 O 4 /M 4 S 4 molecular building blocks with the metal atom M corresponding to one of the 3d late transition metal atoms i.e.…”

Application of Ion Mobility-Mass Spectrometry to the Study of Ionic Clusters

“…20) Next we show the results of investigation of stable chemical compositions for rst-row transition metal oxide cluster ions. As for the stable composition of the transition metal oxides, there have been several investigations using CID, 21,22) photodissociation 23) and thermal heating. 24) However no de nite was known from such experiments so far.…”