Vibrational distribution in NO(X2Π) formed by self quenching of NO A 2Σ+ (v = 0)

Abstract

Time-resolved FTIR has been used to study the emission from the NO X ²Π (v) products formed both by fluorescence and by collisional self quenching of the NO A ²Σ⁺ (v = 0) state. Vibrational excitation has been observed in ground state NO with populations up to at least v = 20. Under conditions where fluorescence is the dominant removal process the nascent distribution in ground state NO(v) was found to be determined by the relative magnitude of the emission coefficients. Collisional quenching by ground state NO populates higher vibrational levels in NO(v) than fluorescence. By comparing distributions acquired at different pressures and by using a surprisal analysis, a nascent distribution of NO(v = 0–20) is estimated for collisional relaxation of NO A ²Σ⁺ (v = 0) by NO. This distribution was found to be slightly hotter than statistical (prior) and showed evidence of oscillations at specific vibrational levels. This work is one of the first to be published concerning the vibrational ground state products of the quenching of electronically excited molecules and the first to report emission over such a large number of vibrational levels.