dc.creator Stanton, J. F. en_US dc.date.accessioned 2008-07-15T13:41:43Z dc.date.available 2008-07-15T13:41:43Z dc.date.issued 2008 en_US dc.identifier 2008-MA-02 en_US dc.identifier.uri http://hdl.handle.net/1811/33400 dc.description Author Institution: Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 en_US dc.description.abstract Spectral lines associated with the NO$_3$ molecule were first detected and reported by Chappuis in the period 1880-1882. Although the carrier of these lines was not determined without ambiguity, it still remains a fact that this may well have represented the first spectroscopic detection of a polyatomic radical. In the intervening century and a quarter, NO$_3$ has emerged as both an important species in the nighttime atmosphere as well as a major challenge for molecular spectroscopy. The difficulties in the spectroscopy lay in the exceedingly complex quantum mechanics that governs the molecule; there are five low-lying electronic states, and vibronic interactions mixing these states are ubiquitous. This talk focuses on the ground electronic state of NO$_3$, which is strongly coupled ({\it via} a pseudo-Jahn-Teller interaction) with an excited state having $^2E^{\prime}$ symmetry that is positioned roughly 2 eV higher in energy. Through use of a model Hamitonian approach, the identity of most vibronic levels within 3000 cm$^{-1}$ of the zero-point level is revealed, and a number of spectroscopic misassignments are corrected and other unassigned lines are properly accounted for. The question the molecular structure of NO$_3$ is discussed towards the end of the talk, where it will be argued that viewing the molecule as a symmetric $D_{3h}$ species is appropriate to understand its spectroscopy, while viewing it as a $C_{2v}$ species effectively rationalizes its remarkably high reactivity. The question of the symmetry associated with the minimum on the adiabatic potential energy surface is largely irrelevant in this regard. en_US dc.language.iso English en_US dc.publisher Ohio State University en_US dc.title DIABATIC MODEL HAMILTONIAN TREATMENTS OF THE NITRATE RADICAL en_US dc.type Article en_US
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