Dynamics of transient speciesviaanion photodetachment

Abstract

The dynamics of chemical reactions are often governed by transient species, including the transition state for activated bimolecular reactions. Such transient species are difficult to study experimentally, but it has proven valuable to prepare and probe transition-state dynamics by the photodetachment of anions with an equilibrium geometry similar to the neutral transition state. In this review, recent experimental advances in photoelectron and photoelectron-photofragment coincidence spectroscopy are discussed, as well as the latest progress in the calculation of multidimensional potential energy surfaces and quantum dynamics calculations that have enabled an extension of studies of transition-state dynamics to increasingly multidimensional polyatomic systems. Examples of important dynamical effects such as mode specificity, tunneling, resonance and product energy disposal in reaction dynamics are discussed.

Loss of CO2 from Monodeprotonated Phthalic Acid upon Photodissociation and Dissociative Electron Detachment

“…It is well known that small molecular anionic systems can undergo a second type of dissociation process induced by UV excitation, in which the system is vertically placed on the reaction coordinate of the neutral radical species generated by electron detachment. 11 For example, dissociative photodetachment of cold deprotonated acetic acid (CH3COO  ) has been studied using photoelectron-photofragment coincidence spectroscopy, giving a complete description of the (CH3COO •  CH3 • + CO2) rearrangement reaction. 12 The dissociative photodetachment mechanism has also been described in deprotonated aryl carboxylic acids, such as benzoic or naphthoic anions, by measurement of the kinetic energy of the neutral species involved in the reaction, that is the remaining unfragmented radical (C6H5COO • or C10H7COO • ) together with the respective photoproducts (C6H5 • + CO2) or (C10H7 • + CO2).…”

Photodetachment of deprotonated aromatic amino acids: stability of the dehydrogenated radical depends on the deprotonation site

“…Though seemingly simple species, fundamental questions regarding the gas-phase structure of deprotonated amino acids and, in particular, the neutral radicals issued from their electron detachment remain unanswered to date. The stability of small dehydrogenated acid radicals has been studied through coincidence techniques 1 . In particular, it has been shown that the simplest, acetyloxyl, loses CO 2 upon photodetachment, with a small barrier (0.1eV)calculated for CO 2 loss 2 .…”

Direct observation of bimolecular reactions of ultracold KRb molecules

“…Studying the dynamics or kinetics of such complexes in the gas phase has typically required ultrafast (13)(14)(15)(16)(17) or stabilizing collisional (18)(19)(20) techniques. Structural investigations of these complexes have been previously obtained by photodetachment (21,22), photoabsorption ( 23), or photodissociation (24). On the basis of the Rice-Ramsperger-Kassel-Marcus (RRKM) theory, the lifetime of an intermediate complex is given by t c ¼ 2pr c =N o , Fig.…”