High-resolution Fourier transform infrared synchrotron spectroscopy of the NO2 in-plane rock band of nitromethane

The high-resolution rotationally resolved Fourier-transform infrared spectrum of the NO2 in-plane rock band (440-510 cm(-1)) of nitromethane (CH3NO2) has been recorded using the Far-Infrared Beamline at the Canadian Light Source, with a resolution of 0.00096 cm(-1). About 1773 transitions reaching the upper state levels m' = 0; K-a' <= 7; J' <= 50 have been assigned using an automated ground-state combination difference program together with the traditional Loomis-Wood approach. These data from the lowest torsional state, m' = 0, were fit using the six-fold torsion-rotation program developed by Ilyushin et al. (2010). The analysis reveals that the rotational energy level structure in the upper vibrational state is similar to that of the ground vibrational state, but the sign and magnitude of high-order constants are significantly changed suggesting the presence of multiple perturbations. (C) 2014 Elsevier Inc. All rights reserved.