Increasing complexity in molecular chemical dynamics

Abstract

Crossed molecular beam (CMB) methods are combined with velocity map imaging (VMI) in order to study the scattering of gaseous polyatomics from colliders of increasing complexity. In addition to this, molecular dynamics (MD) simulations are used to model the surfaces of a range of atmospherically relevant fatty acids and mixtures of hydrocarbons. The first known measurements of k-j-k′ correlations for an inelastic scattering system, are reported. The scattering system of choice was NO(A, 2𝚺+) + Ne, with the NO(A) initially rotationally excited to the N = 4, j = 3.5 state, making this also one of only a small number of studies of initially rotationally excited NO(A). During excitation molecules are aligned using linearly polarised light, allowing for the extraction of both differential cross sections (DCSs) and 𝑇0 2 polarisation dependent DCSs (PDDCSs). Results of scattering experiments involving NH3 and a series of atomic and molecular colliders of increasing size are reanalysed using a fitting routine modified by the author. Where Ar and D2 are used as co-colliders, the DCSs extracted are compared to those from quantum scattering (QS) calculations. Good experiment-theory agreement is found for the work involving Ar. For the NH3 + D2 work, however, a much higher degree of product D2 excitation is observed in the experiments than predicted based on theory. DCSs are also extracted from data on the scattering of NH3 from a series of hydrocarbons, representing one of the first systems involving polyatomic-polyatomic scattering. MD simulations of the vacuum-liquid interfaces of members of the oleic acid family, and of mixtures of squalane and squalene, are presented, with an emphasis placed on which groups are preferentially present at the surface, as opposed to the bulk. An above-statistical distribution of methyl groups is observed at the interface, with the implications of this for atmospheric pollution cycles discussed.