A Discharge Flow-Photoionization Mass Spectrometric Study of the NO3(2A2') Radical: Photoionization Spectrum, Adiabatic Ionization Energy, and Ground State Symmetry

Abstract

The photoion efficiency spectrum of the nitrate radical (NO[sub 3]) was measured over the region [lambda] = 90[minus]104 nm by using a discharge flow-photoionization mass spectrometer apparatus coupled to a synchrotron radiation source. NO[sub 3] was generated by the reaction of fluorine atoms with nitric acid. A value of 12.57 [+-] 0.03 eV was obtained for the adiabatic ionization energy (IE) of NO[sub 3] from photoion thresholds, corresponding to the NO[sub 3][sup +]([sup 1]A[sub 1][prime]) [yields] NO[sub 3]([sup 2]A[sub 2][prime]) transition. These direct ionization measurements are the first to be reported for the NO[sub 3] radical. Relative energetics and optimized geometries for ground state NO[sub 3] and several states of NO[sub 3][sup +] were determined in both D[sub 3h] and C[sub 2v] symmetries using multiconfiguration self-consistent-field calculations. The results of the present study strongly suggest that the neutral ground state of NO[sub 3] has D[sub 3h] symmetry. This conclusion is based on the following observations. 31 refs., 4 figs., 3 tabs.