Dissociative photodetachment of SO2·SO2−: evidence for the S–O bound dimer

Dissociative Photodetachment Dynamics of the OH-(C2H4) Anion Complex

Photoelectron-photofragment coincidence (PPC) measurements on OH^-(C₂H₄) anions at a photon energy of 3.20 eV revealed stable and dissociative photodetachment product channels, OH-C₂H₄ + e^- and OH + C₂H₄ + e^-, respectively. The main product channel observed was dissociation to the reactants (>67%), OH + C₂H₄ (v = 0, 1, 2) + e^-, where vibrational excitation in the C-H stretching modes of the C₂H₄ photofragments corresponds to a minor channel. The low kinetic energy release (KER) of the dissociating fragments is consistent with weak repulsion between the OH + C₂H₄ reactants near the transition state as well as the partitioning of energy into rotation of the dissociation products. An impulsive model was used to account for rotational energy partitioning in the dissociative photodetachment (DPD) process and showed good agreement with the experimental results. The low KER of the dissociating fragments and the similarities in the photoelectron spectra between stable and dissociative events support a mechanism involving the van der Waals complex formed upon photodetachment of OH^-(C₂H₄) as an intermediate in the dominant OH + C₂H₄ + e^- dissociative channel.

Invited Review Article: Photofragment imaging

Photodissociation studies in molecular beams that employ position-sensitive particle detection to map product recoil velocities emerged thirty years ago and continue to evolve with new laser and detector technologies. These powerful methods allow application of tunable laser detection of single product quantum states, simultaneous measurement of velocity and angular momentum polarization, measurement of joint product state distributions for the detected and undetected products, coincident detection of multiple product channels, and application to radicals and ions as well as closed-shell molecules. These studies have permitted deep investigation of photochemical dynamics for a broad range of systems, revealed new reaction mechanisms, and addressed problems of practical importance in atmospheric, combustion, and interstellar chemistry. This review presents an historical overview, a detailed technical account of the range of methods employed, and selected experimental highlights illustrating the capabilities of the method.