Excited state dynamics of NO3

Abstract

The fluorescence decay of NO3 excited to vibronic levels between the origin at 661.9 and ∼606 nm is measured and found to be nonexponential. An exponential fit to the long-lived portion of the decay gives an apparent, collision-free lifetime of 340±20 μs. Electronic quenching rates have been measured for a variety of collision partners including He, N2, O2, C3H8, and HNO3. Our results are interpreted in terms of the Douglas effect, i.e., an extensive coupling of excited electronic levels with nonemissive vibronic levels of the ground electronic state. This coupling is likely responsible for the anomalously long lifetime and the apparent diffuseness of the absorption spectrum.

Ab initio investigation of the vertical and adiabatic excitation spectrum of NO3

“…This finding is only insofar surprising because in all experimental investigations of the photodissociation process, it was assumed that the photoactive 2 EЈ state ͑3͒ is adiabatically connected to the fragments in their ground electronic states. 10 FIG. 2.…”

“…[9][10][11][12] Nelson et al 9,10 report on an unusu-ally long lifetime of the B 2 EЈ state and explained this finding by Douglas coupling. 13 In contrast, Ishiwata et al found a much shorter lifetime, 11 but Nelson's results were confirmed by a recent supersonic jet study.…”

Conflicting Observations Resolved by a Far IR and UV/Vis Study of the NO3 Radical

“…[4,5] Numerous spectroscopic studies have sought to obtain the equilibrium symmetry and the assignment of the vibrational transitions in the ground electronic state. Important recent studies include: 1) photoelectron (PE) spectroscopic studies of both the nitrate anion [6,7] and the NO 3 radical, [8] 2) laser-induced fluorescence (LIF) spectra of the nitrate radical, [9,10] as well as a recent reanalysis of the vibronic levels obtained from these spectra, aided by non-adiabatic computations, [11] 3) the analysis of high-resolution diode laser and FTIR gas phase spectra which were obtained in the region 700 to 1520 cm À1 , [12,13] and later extended to 1300-2800 cm À1 [14][15][16] and to the near infrared, [17] and 4) a neonmatrix FTIR study on NO 3 in the range from 450 to 6000 cm À1 . [18] From the analysis of the recent spectra, D 3h symmetry was determined for the free NO 3 radical in the X $ 2 A 2 ' ground state.…”

Examination of the 2A′2 and 2E″ states of NO3 by ultraviolet photoelectron spectroscopy of NO−3

“…observed is the lE' _2A ~ band, with its origin at 662 nm. This band has been studied using absorption 19-21 and fluorescence excitation 7.8, 22 spectroscopy, but the diffuse vibrational structure evident in these spectra has not been fully analyzed. Johnston and co-workers 23 see no rotational structure in this band even at 0.007 cm .…”