High resolution polarization spectroscopy and laser induced fluorescence of CO₂ around 2 mμm

Abstract

High resolution Infrared Polarisation Spectroscopy (IRPS) and Infrared Laser Induced Fluorescence (IRLIF) techniques were used to probe CO 2/N2 binary gas mixture at atmospheric pressure and ambient temperature. The probed CO2 molecules were prepared by laser excitation to an overtone and combination ro-vibrational state (1201, J=15) of CO2, centred at 4988.6612 cm-1. IRPS and IRLIF line profiles were recorded for several CO2/N2 binary mixtures. The observed IRLIF line shapes have the expected Lorentzian form while the observed IRPS line shapes are narrower by a factor of two than those recorded with the IRLIF and appear to have a Lorentzian-cubed profile. The recorded line profiles provide measurements of the pressure-broadening coefficient directly at atmospheric pressure. The Full-Width-Half-Maxima (FWHM) pressure broadening coefficients are measured, based on IRLIF, to be 0.2174±0.0092 cm-1atm-1 and 0.1327 ±0.0077 cm-1atm-1 for self- and N2 collision broadening, respectively. The broadening coefficients obtained based on IRPS were measured to be ~8% larger than those obtained with IRLIF. © EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007.