High-resolution FTIR spectrum and rotational structure of the ν8 band of methylene chloride

Abstract

The high-resolution Fourier-transform infrared spectrum of the ν8 band of methylene chloride (CH2Cl2) was measured in the range 1230-1305 cm-1. The band shows the typical A-type contour of an asymmetric-top molecule. A rovibrational structure analysis of the spectrum provided a set of accurate upper state constants up to some quartic centrifugal distortion constants which could reliably reproduce the observed spectrum. The absorption lines of the two isotopomers CH2 35Cl2 and CH2 35Cl37Cl were identified. A total of 1314 transitions for CH2 35Cl2 and 595 transitions for CH2 35Cl37Cl were assigned and fitted with an isotopic band center shift of about 0.035 cm-1 for this CH2 wagging fundamental mode. The measurement on the integrated band intensity was also performed and gave a value of (1.57 ± 0.08) × 10-17 cm/ molecule, taking into account the contribution from the hot bands in this region. Comparison between the observed and calculated band intensity gave an estimate of the dipole transition moment component along the a-axis at a value of |μa| = 0.218 D. © 1996 Academic Press, Inc.