Communication: IR spectroscopy of neutral transition metal clusters through thermionic emission

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Structural determination of niobium-doped silicon clusters by far-infrared spectroscopy and theory

In this work, the structures of cationic Si_nNb^+ (n=4–12) clusters are determined using the combination of infrared multiple photon dissociation (IR-MPD) and density functional theory (DFT) calculations. The experimental IR-MPD spectra of the argon complexes of Si_nNb^+ are assigned by comparison to the calculated IR spectra of low-energy structures of Si_nNb^+ that are identified using the stochastic ‘random kick’ algorithm in conjunction with the BP86 GGA functional. It is found that the Nb dopant tends to bind in an apex position of the Sin framework for n=4–9 and in surface positions with high coordination numbers for n=10–12. For the larger doped clusters, it is suggested that multiple isomers coexist and contribute to the experimental spectra. The structural evolution of Si_nNb^+ clusters is similar to V-doped silicon clusters (J. Am. Chem. Soc., 2010, 132, 15589–15602), except for the largest size investigated (n=12), since V takes an endohedral position in Si_12V^+. The interaction with a Nb atom, with its partially unfilled 4d orbitals leads to a significant stability enhancement of the Sin framework as reflected, e.g. by high binding energies and large HOMO–LUMO gaps.crosscheck: This document is CrossCheck deposited related_data: Supplementary Information copyright_licence: The PCCP Owner Societies have an exclusive publication licence for this journal copyright_licence: This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0) history: Received 26 November 2015; Accepted 20 January 2016; Accepted Manuscript published 27 January 2016; Advance Article published 8 February 2016; Version of Record published 17 February 2016status: publishe

The structures of neutral transition metal doped silicon clusters, SinX (n=6-9; X = V, Mn)

We present a combined experimental and theoretical investigation of small neutral vanadium and manganese doped silicon clusters SinX (n = 6−9, X = V, Mn). These species are studied by infrared multiple photon dissociation and mass spectrometry. Structural identification is achieved by comparison of the experimental data with computed infrared spectra of low-lying isomers using density functional theory at the B3P86/6-311+G(d) level. The assigned structures of the neutral vanadium and manganese doped silicon clusters are compared with their cationic counterparts. In general, the neutral and cationic SinV0,+ and SinMn0,+ clusters have similar structures, although the position of the capping atoms depends for certain sizes on the charge state. The influence of the charge state on the electronic properties of the clusters is also investigated by analysis of the density of states, the shapes of the molecular orbitals, and NBO charge analysis of the dopant atom.status: publishe

Infrared-induced reactivity of N2O on small gas-phase rhodium clusters

Far- and mid-infrared multiple photon dissociation spectroscopy has been employed to study both the structure and surface reactivity of isolated cationic rhodium clusters with surface-adsorbed nitrous oxide, RhnN2O+ (n = 4−8). Comparison of experimental spectra recorded using the argon atom tagging method with those calculated using density functional theory (DFT) reveals that the nitrous oxide is molecularly bound on the rhodium cluster via the terminal N-atom. Binding is thought to occur exclusively on atop sites with the rhodium clusters adopting close-packed structures. In related, but conceptually different experiments, infrared pumping of the vibrational modes corresponding with the normal modes of the adsorbed N2O has been observed to result in the decomposition of the N2O moiety and the production of oxide clusters. This cluster surface chemistry is observed for all cluster sizes studied except for n = 5. Plausible N2O decomposition mechanisms are given based on DFT calculations using exchange-correlation functionals. Similar experiments pumping the Rh−O stretch in RhnON2O+ complexes, on which the same chemistry is observed, confirm the thermal nature of this reaction

Structure Determination of Anionic Metal Clusters via Infrared Resonance Enhanced Multiple Photon Electron Detachment Spectroscopy

We report vibrational spectra of anionic metal clusters, measured via electron detachment following resonant absorption of multiple infrared photons. To facilitate the sequential absorption of the required large number of photons, the cluster beam interacts with the infrared radiation inside the cavity of a free electron laser. Far-infrared spectra of the bare metal cluster anion Nb₁₀^– as well as of the Nb₆C^– anion are measured in the 130–1000 cm^–1 range. The structures of these clusters can be unambiguously determined by comparison with calculated spectra of the putative global minima structures, identified by density functional theory calculations

Structure determination of anionic metal clusters via infrared resonance enhanced multiple photon electron detachment spectroscopy

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