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Title: Spectroscopy and dynamics of metal clusters
Author: Hamilton, Suzanne M.
ISNI:       0000 0004 2701 1973
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2011
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A range of spectroscopic and computational techniques have been applied to the study of three metal cluster systems: vanadium monoxide, the Au2 molecule, and RhnN2O+ clusters. A new instrument has been built for spectroscopy experiments on metal clusters, consisting of a laser ablation cluster source and a linear time-of-flight mass spectrometer. The instrument was characterised using nitric oxide spectroscopy and applied to the electronic REMPI spectrum of vanadium oxide in the visible region. The rotational constants and band origins of several known states have been determined, and the observation of a new spin-forbidden transition has been used to connect the energies of the quartet and doublet manifolds of VO. A new 3 2Π state was also observed and characterised. The photoionisation and photodissociation of Au2 were then studied at 157 nm, and between 35500 and 37200 cm-1 with another new instrument recently constructed in the group. Excited and ground state Au photofragments were produced in both spectral regions, and have been detected and assigned using velocity map imaging. The 157 nm photodissociation produced gold atom products in the seven highest-energy accessible channels in a single-photon dissociation process. The complex near-UV spectrum involved two-photon excitation to two 0g+ excited states close to their dissociation thresholds, followed by predissociation to thirteen different Au product channels. The branching ratios for dissociation into each of these channels varied across the spectrum as different dissociation limits and curve crossings occurred. The mid- and far-infrared multiple-photon dissociation spectra of RhnN2O+ clusters have been recorded using the argon-tagging action spectroscopy technique and free electron laser radiation. The results have been compared to density functional theory calculations to deduce the nature of the binding and the likely low-lying electronic and geometrical structures. The N2O was found to be molecularly adsorbed on the surface of the cluster but, upon infrared heating of the complex via the N2O vibrational modes, was observed to undergo a reaction, producing N2 and cluster oxides RhnO+. The reaction is believed to be thermal and mode-independent, but the efficiency of the surface reaction does vary with cluster size, with the n=5 cluster showing no detectable reaction.
Supervisor: Mackenzie, Stuart R. Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Laser Spectroscopy ; Computational chemistry ; Physical Sciences ; Mass spectrometry ; Chemistry & allied sciences ; Physical & theoretical chemistry ; Catalysis ; Surface chemistry