Temperature Dependence of the Electronic Absorption Spectrum of NO.

The nitrogen dioxide (NO) radical is composed of the two most abundant elements in the atmosphere, where it can be formed in a variety of ways including combustion, detonation of energetic materials, and lightning. Relevant also to smog and ozone cycles, together these processes span a wide range of temperatures. Remarkably, high-resolution NO electronic absorption spectra have only been reported in a narrow range below about 300 K.

Aromatic Stabilization and Hybridization Trends in Photoelectron Imaging of Heterocyclic Radicals and Anions.

We examine the photoelectron spectra and laboratory-frame angular distributions in the photodetachment of furanide (C4H3O(-)), thiophenide (C4H3S(-)), and thiazolide (C3H2NS(-)) and compare the results to the previously reported studies of pyridinide (C5H4N(-)) and oxazolide (C3H2NO(-)). Using the mixed s-p model for the angular distributions, the results are interpreted in terms of the effective fractional p character of the highest-occupied molecular orbitals of these heterocyclic anions, revealing trends related to the aromaticity. We conclude that aromatic stabilization across a series of systems may be tracked using the photoelectron angular distributions.

Photoelectron angular distributions for states of any mixed character: an experiment-friendly model for atomic, molecular, and cluster anions.

We present a model for laboratory-frame photoelectron angular distributions in direct photodetachment from (in principle) any molecular orbital using linearly polarized light. A transparent mathematical approach is used to generalize the Cooper-Zare central-potential model to anionic states of any mixed character. In the limit of atomic-anion photodetachment, the model reproduces the Cooper-Zare formula.

Spectroscopy of the breaking bond: the diradical intermediate of the ring opening in oxazole.

Bond breaking is a challenging problem in both experimental and theoretical chemistry, due to the transient nature and multi-configurational electronic structure of dissociating molecules. We use anion photodetachment to probe the diradical interactions in the ring-opening reaction of oxazole and obtain a self-consistent picture of the breaking bond. Starting from the closed-shell cyclic molecule, the reaction is launched on the anion potential, as an attached electron cleaves a carbon-oxygen bond.

Photoelectron angular distributions of pyridinide: a benchmark application of the mixed s-p model to a truly polyatomic anion.

We report a photoelectron imaging study of the pyridinide anion, C5H4N(-), obtained by deprotonation of pyridine at the C4 position. The photoelectron angular distributions are used to test the theoretical formalism for photodetachment from mixed-character s-p states, demonstrating its first application to a truly polyatomic system. The mixed s-p model describes the initial state of the anion in terms of a superposition of one s orbital and one p orbital centered on the deprotonated carbon.

Selective deprotonation of oxazole and photoelectron imaging of the oxazolide anion.

A photoelectron imaging study of the oxazolide anion obtained by selective deprotonation of oxazole at the C2 position is reported. The photodetachment transitions observed at 355, 392, and 532 nm are assigned to the ground state of the neutral oxazolyl σ radical. A Franck-Condon analysis of this transition aids in the first determination of the adiabatic electron affinity of oxazolyl, EA = 2.