Methyl Halide Cluster Anion Photoelectron Spectra and Angular Distributions as a Probe of Electron-Molecule Interactions

This dissertation describes the development of a method for studying electron &ndash molecule interactions using cluster anion photodetachment. Photodetachment from an atomic centered cluster anion produces a free electron and a residual neutral species at a geometry near that of the unperturbed neutral ground state. Evidence of the free electron &ndash molecule interactions, manifested in the photoelectron spectra and angular distributions, are elucidated through comparison to photodetachment data from the unsolvated atomic anion in question. Results are presented from number of monosolvated anion studies, including I&minus· CH3I, I&minus· CH3Br, I&minus· CH3Cl and Cl&minus· CH3I, as well as a study of the disolvated anion I&minus·: CH3I)2. The findings demonstrate the usefulness of this method as a probe of anion &ndash molecule solvation structure, long range electron &ndash molecule interactions, solvent electronic structure, and the influence of the cluster environment upon photodetachment dynamics. A detailed description of the experimental methods, including the construction and operation of the instrumentation, is presented. Applications of the method towards further study of electron &ndash neutral resonances and electron initiated chemical reactions are discussed

Vibronic coupling in the superoxide anion: The vibrational dependence of the photoelectron angular distribution

We present a comprehensive photoelectron imaging study of the O₂(X³Σg⁻,v′=0–6)←O₂⁻(X²Πg,v′′=0) and O₂(a¹Δg,v′=0–4)←O₂⁻(X²Πg,v′′=0)photodetachment bands at wavelengths between 900 and 455 nm, examining the effect of vibronic coupling on the photoelectron angular distribution (PAD). This work extends the v′=1–4 data for detachment into the ground electronic state, presented in a recent communication [R. Mabbs, F. Mbaiwa, J. Wei, M. Van Duzor, S. T. Gibson, S. J. Cavanagh, and B. R. Lewis, Phys. Rev. A82, 011401–R (2010)]. Measured vibronic intensities are compared to Franck–Condon predictions and used as supporting evidence of vibronic coupling. The results are analyzed within the context of the one-electron, zero core contribution (ZCC) model [R. M. Stehman and S. B. Woo, Phys. Rev. A23, 2866 (1981)]. For both bands, the photoelectron anisotropy parameter variation with electron kinetic energy,β(E), displays the characteristics of photodetachment from a d-like orbital, consistent with the π∗g 2p highest occupied molecular orbital of O₂⁻. However, differences exist between the β(E) trends for detachment into different vibrational levels of the X³Σg⁻ and a ¹Δg electronic states of O₂. The ZCC model invokes vibrational channel specific “detachment orbitals” and attributes this behavior to coupling of the electronic and nuclear motion in the parent anion. The spatial extent of the model detachment orbital is dependent on the final state of O₂: the higher the neutral vibrational excitation, the larger the electron binding energy. Although vibronic coupling is ignored in most theoretical treatments of PADs in the direct photodetachment of molecular anions, the present findings clearly show that it can be important. These results represent a benchmark data set for a relatively simple system, upon which to base rigorous tests of more sophisticated models.The authors gratefully acknowledge support by the National Science Foundation Grant No. CHE-0748738 and ANU ARC Discovery Projects under Grant Nos. DP0666267 and DP0880850

Vibronic coupling in the superoxide anion: the vibrational dependence of the photoelectron angular distribution

We present a comprehensive photoelectron imaging study of the O2(X 3Σg−,v′ = 0–6)←O2−(X 2Πg,v″ = 0) and O2(a 1Δg,v′ = 0–4)←O2−(X 2Πg,v″ = 0) photodetachment bands at wavelengths between 900 and 455 nm, examining the effect of vibronic coupling on the photoelectron angular distribution (PAD). This work extends the v′ = 1–4 data for detachment into the ground electronic state, presented in a recent communication. Measured vibronic intensities are compared to Franck–Condon predictions and used as supporting evidence of vibronic coupling. The results are analyzed within the context of the one-electron, zero core contribution (ZCC) model. For both bands, the photoelectron anisotropy parameter variation with electron kinetic energy, β(E), displays the characteristics of photodetachment from a d-like orbital, consistent with the πg∗ 2p highest occupied molecular orbital of O2−. However, differences exist between the β(E) trends for detachment into different vibrational levels of the X 3Σg− and a 1Δg electronic states of O2. The ZCC model invokes vibrational channel specific “detachment orbitals” and attributes this behavior to coupling of the electronic and nuclear motion in the parent anion. The spatial extent of the model detachment orbital is dependent on the final state of O2: the higher the neutral vibrational excitation, the larger the electron binding energy. Although vibronic coupling is ignored in most theoretical treatments of PADs in the direct photodetachment of molecular anions, the present findings clearly show that it can be important. These results represent a benchmark data set for a relatively simple system, upon which to base rigorous tests of more sophisticated models

Observation of vibration-dependent electron anisotropy in O−2 photodetachment

Photoelectron angular distributions (PADs) recorded for the O2(X 3Σg-) ← O2-(X 2Πg) band show significant vibrational dependence. Experimental evidence of vibrational influence on the PAD has, to date, been sparse. Consequently, little attention has

Photodetachment velocity map imaging of the 1A′←2A′ transition in the AuOH anion

Abstract not availableBradley R. Visser, Matthew A. Addicoat, Jason R. Gascooke, Xinxing Zhang, Kit Bowen, Warren D. Lawrance, Gregory F. Meth