The near-infrared bands of NO2 observed by high-resolution Fourier-transform spectroscopy

Abstract

Fourier-transform absorption spectra of NO2 at 298 K were recorded between 9000–15 000 cm−1 at Doppler-limited resolution (0.012 cm−1), in the region near the à 2B2–X̃ 2A1 conical intersection. The strong rovibronic bands are rather isolated and organized into polyads which can be assigned by the number of bending quanta of the à 2B2 state, corresponding to the transitions with the largest Franck–Condon factors. Around 9735 cm−1, where the origin of the à 2B2–X̃ 2A1 vibronic band system is located and up to about 11 200 cm−1, hot bands dominate the spectrum. The complexity of the spectrum increases with energy due to an increasing density of à 2B2 and X̃ 2A1 vibrational levels. The rotational structure is dense and irregular as already observed for higher bands.