High-resolution analysis of the 12.6 mum spectral region of the nitryl chloride ClNO2 molecule

Abstract

The 12.6 mum region of nitryl chloride (ClNO2) has been recorded at high resolution (0.00102 cm-1) using a Fourier transform spectrometer and the SOLEIL synchrotron light source. ClNO2 was found during our studies of chlorine nitrate and, after fractional distillations it was introduced into a multipass White cell made of inert materials, with an optical path length of 5.4 m. 320 scans were recorded for the range 600-980 cm-1 at a total pressure of 0.23 hPa and a temperature of 250 K. A thorough analysis of the v2, 2v6 and 2v3 bands of 35ClNO2 and of the v2 band of 37ClNO2 falling in this region has been carried out using a Hamiltonian model which takes explicitly into account the numerous resonances affecting the ro-vibrational energy levels; especially the C-type Coriolis resonance between the v2 and the v3 +v6 modes. These two modes are only separated by less than 20 cm-1 and are thoroughly mixed. From the fittings, the following band centers were derived: v0(v2) = 792.761264(60) cm-1, v0(v3 +v6) = 775.8923(20) cm-1, v0(2v3) = 734.183576(20) cm-1 and v0(2v6) = 819.836727(90) cm-1 for 35ClNO2 and v0(v2) = 792.258284(30) cm-1 and v0(v3 +v6) = 774.6826(30) cm-1 for 37ClNO2 where the uncertainties are one standard deviation. Due to their sharp Q branches falling into an atmospheric "window", the detection of the v2 bands might be an advantageous route for future attempts to quantify atmospheric ClNO2, using infrared techniques.