New analysis of line positions of the ν3 bands of 35ClNO2 and 37ClNO2 around 370 cm−1

Abstract

A new investigation of the ν3 bands of 35ClNO2 and37ClNO2, located around 370 cm−1 has been performed using a high resolution (0.00102 cm−1) Fourier transform spectrum recorded at SOLEIL with highly improved experimental conditions as compared to previous work [Orphal J, Morillon-Chapey M, Klee S, Mellau GC, Winnewisser M. J Mol Spectrosc 1998;190:101–6]: (i) the use of synchrotron radiation which resulted in a better signal-to-noise ratio; (ii) a resolution twice better; (iii) a low temperature (221 K) with an optical path length of 8.16 m, allowing low pressure (0.025 hPa) in the sample leading to a well resolved spectrum. As a consequence, significantly better results than previously were obtained. Thanks to the new experimental conditions, the line assignments were pursued up to higher J and Ka quantum number values, J = 83 and Ka = 44. For both isotopomers, a total of 6331 transitions were reproduced with a root-mean-square deviation of 2 × 10−4 cm−1 using a Watson-type A-reduced Hamiltonian. Improved rotational and centrifugal distortion constants for the ν3 fundamental bands of 35ClNO2 and37ClNO2 have been determined. The band centers are 370.1510773(92) cm−1 for the ν3 fundamental band of 35ClNO2 and 364.5218094(96) cm−1 for the ν3 fundamental band of 37ClNO2. The synthetic line list obtained in this study could be interesting for future measurements of ClNO2 in the atmosphere, e.g. using the new space mission FORUM which is one of the concepts chosen by ESA to be developed further and which opens up a new window (150–1400 cm−1) for understanding and quantifying the radiative processes, as well as air quality and pollution effects.