Spectroscopy and interactions of metal and metal cation complexes

Abstract

The work in this thesis looks at the spectroscopy and interactions of metals and metal cation complexes. There are two aspects of this vast subject that are considered: the electronic spectroscopy of Au-RG complexes and the ion-molecule chemistry of metals important in the mesosphere-lower thermosphere (MLT) region of the atmosphere. The spectroscopy of the molecular states in the vicinity of the strong Au 2P3/2, 1/2 ← 2S1/2 atomic transition, have been studied for the Au-RG (RG = Ne, Ar, Kr, Xe) series using resonance enhanced multiphoton ionization (REMPI). The spectroscopy of these systems was more involved than expected and high level ab initio calculations were required to complement and aid interpretation of the REMPI spectra obtained. Two main effects were seen to influence the spectroscopy in this energetic region — the mixing between D2Π1/2 and E2Σ1/2+ states through spin-orbit interactions and the interaction of lower lying states arising from the Au(2D) + RG (1S0) asymptote, resulting in predissociation being observed. The MLT is the only region of the Earth’s atmosphere in which metals exist in a free atomic state. It is known that their presence in this region occurs via the ablation of meteors entering the upper atmosphere, but certain aspects of their chemistry are still unclear. Using high level ab initio theory, spectroscopic constants were determined for metal cation complexes that can be formed in this region. These values are used by collaborators in conjunction with laboratory measurement to establish accurate rate coefficients that will allow the ion-molecule chemistry of calcium and magnesium in the MLT region to be modelled