Molecular Photoionization Dynamics at Threshold Energies

Abstract

Listen

Translate article

Photoinduced molecular fragmentation processes offer a unique opportunity for studying collision dynamics in which the angular momenta, relative energies and spatial orientations of the interacting particles are constrained. Examples include neutral photodissociation which leads to chemical bond cleavage, and photoionization which results in the formation of a free electron and molecular cation. The half-collision view of photofragmentation processes provides the link between the highly detailed state-to-state information derived from such studies and the less tractable full collision problems such as reactive scattering and inelastic electron scattering. Central to these collision processes is the nature of the close range complex or “transition state” whose time-evolution determines the fragment yields and their state distributions. Except for a few experiments involving simple diatomic molecules, however, time-resolved measurements of the photoexecited collision complex are not usually feasible.1 Instead, the dynamics of the fragmentation process are inferred from measurements of the asymptotic product state distributions. To obtain an adequate description of the fragmentation dynamics, it becomes necessary to completely characterize the quantum state distributions of the fragments as well as their relative translational energies and spatial correlations. Much recent effort in photodissociation dynamics involves the development of probe schemes, e.g. Doppler profile analyses, which can provide a maximum amount of product information (scalar and vector) with the minimum number of measurements and experimental configurations.2