Electronic Structure and Electronic Spectrum of Nitrogen Dioxide. III Spectral Interpretation

Abstract

The excitation energies, potential-energy surfaces, and oscillator strengths computed in the previous paper are discussed in light of experimentally reported spectroscopic data, namely absorption, fluorescence, chemiluminescence, predissociation, photolysis, and the absence of phosphorescence. It is found that the main components of the visible spectrum are due to the transitions B21 ← 2A1, and B22 ← 2A1, with the B22 state being responsible for the observed fluorescence emission. The anomalous fluorescence lifetime is also discussed.

Parts-per-trillion-level detection of nitrogen dioxide by cantilever-enhanced photo-acoustic spectroscopy

“…The photo-acoustic signal is linear up to the maximum average chopped power of 4.7 W. There is no indication of photochemical dissociation of NO 2 , which would have decreased the CEPAS signal at high power levels. The observed high linearity is expected because the photochemical dissociation becomes strong only below 415 nm [20]. The noise of the background signal within the entire optical power range was found to be constant.…”

Global Elucidation of Self-Consistent Field Solution Space Using Basin Hopping

“…Although quartet states arising from spin-forbidden transitions are proposed to contribute to the visible absorption spectrum, the absence of phosphorescence in NO 2 implies intersystem crossing facilitated by unusually large spin−orbit coupling. 57,58 Indeed, the absence of long-lived quartet states has been invoked in rationalization of the observed kinetics of hydroxyl radical formation from electronically excited NO 2 and H 2 O. 59,60 The nature of the intersystem crossing can be examined adiabatically using RG solutions to provide a description of spin-crossing processes.…”

Primary Processes in the Photolysis of NO2

“…56), we assume that a thermal distribution of rotational energies is practically maintained during the reaction. In this case, Equation (18) transforms into a simpler master equation…”

“…N,] 2: P(E,J/E',J')rt(E',J')dE' (18). R is the total rate of light absorption, P ( E , J / E ' , J ' ) a collisional transition probability from state (E',J') into state (E.J).…”