Line positions, intensities and self-broadening coefficients for the ν5 band of methyl chloride

Abstract

High resolution Fourier transform spectra have been recorded around 6.9μm at room temperature using a rapid scan Bruker IFS 120 HR interferometer (unapodized Bruker resolution=0.005cm−1). Transitions of both 12CH335Cl and 12CH337Cl isotopologues belonging to the ν5 perpendicular band have been studied. Line positions, intensities, and self-broadening coefficients have been retrieved using a multispectrum fitting procedure that allowed to fit simultaneously the whole set of experimental spectra recorded at various pressures of CH3Cl. The wavenumber calibration has been performed using the frequencies of CO2 transitions. The transition dipole moments squared have been determined for each measured line and the whole set of measurements has been compared with previous measurements and with values from HITRAN and GEISA databases. The rotational J and K dependencies of the self-broadening coefficients have been clearly observed and modeled using empirical polynomial expansions. The average accuracy of the line parameters obtained in this work has been estimated to be between 0.1×10−3 and 1×10−3cm−1 for line positions, between 2% and 5% for line intensities and between 5% and 10% for self-broadening coefficients depending on the transitions.