Identification, Structure, and Spectroscopy of Neutral Vanadium Oxide Clusters

Abstract

Neutral vanadium oxide clusters are studied by photoionization time-of-flight (TOF) mass spectroscopy, electronic spectroscopy, and density functional theory (DFT) calculations. Mass spectra of vanadium oxide clusters are observed by photoionization with lasers of three different wavelengths: 118, 193, and 355 nm. Mechanisms of 118 nm single photon ionization and 193 and 355 nm multiphoton ionization/fragmentation of vanadium oxide clusters are discussed on the basis of observed mass spectral patterns and line widths of the mass spectral features. Only the 118 nm laser light can ionize vanadium oxide neutral species by single photon ionization without fragmentation. The stable vanadium oxide neutral clusters under saturated oxygen growth conditions are found to be of the form (VO 2 ) x (V 2 O 5 ) y . Structures of the first few members of this series of clusters are determined through high level DFT calculations. Fragmentation of this series of clusters through 355 and 193 nm multiphoton ionization processes is discussed in light of these calculated structures. The B ˜2B 2 r X ˜2A 1 transition is observed for the VO 2 neutral species, and ν 1 and ν 2 vibrations are assigned for both electronic states. From this spectrum, the VO 2 rotational and vibrational temperatures are found to be ∼50 and ∼700 K, respectively.

Density functional theory study of the oxidation of methanol to formaldehyde on a hydrated vanadia cluster

“…The investigation of gas-phase cluster reactivity both from experimental and theoretical points of view has proven to bring valuable information on the elementary steps involved. Gas-phase clusters can be easily obtained and analyzed in neutral, 1 cationic, 2 and anionic forms, [3][4][5] and they serve as excellent models for complex catalytic systems. 6,7 In this work, we use a vanadia cluster to determine the catalytic mechanism of methanol oxidation in hydrated conditions.…”

Dynamics and fragmentation of van der Waals clusters: (H2O)n, (CH3OH)n, and (NH3)n upon ionization by a 26.5eV soft x-ray laser

“…In general, single photon ionization is a good way to study van der Waals and hydrogen bonded clusters since less fragmentation of the parent cluster ions occurs compared to EI and MPI. We have previously demonstrated that, if 10.5 eV is sufficient energy for the ionization of a cluster, 37,38 a 118 nm vuv laser provides a nonresonant soft ionization for metal oxide and methanol clusters, 37,38 as fragmentation is minimized during the ionization process. The 10.5 eV photon, however, is not energetic enough to meet the VIE of ͑H 2 O͒ n .…”

A Topological method for global optimization of clusters: Application to (TiO2)n (n = 1–6)

“…Two predominant components, that is, Ti n O 2n-2 and Ti n O 2n-1 , were indicated in the spectrometry and the former exhibits larger correlated fluctuations. [13] In contrast, main products in the single-photon ionization experiment were predicted to be the Ti n O 2n and Ti n O 2nþ1 clusters by Matsuda and Bernstein [14] Nevertheless, both studies suggested that the cluster growth process is predominated by addition of TiO 2 species. [13,14] Helden et al applied infrared resonance enhanced multiphoton ionization to study the titanium oxide in the gas phase.…”