Pressure-Broadening and Cross-Relaxation Rates of Rotation–Inversion Transitions in the ν4Band of NH3Perturbed by CO2

• Published in: Journal of molecular spectroscopy Vol. 176; no. 1; pp. 162 - 168
• Main Authors: Aroui, H., Picard-Bersellini, A., Chevalier, M., Broquier, M., Gherissi, S.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.03.1996; Elsevier
• Subjects: Chemical Sciences; or physical chemistry; Theoretical and
• ISSN: 0022-2852; 1096-083X
• DOI: 10.1006/jmsp.1996.0073

Measurements of pressure-broadening and cross-relaxation rates of rotation–inversion transitions in the ν4band (1470–1600 cm−1) of NH3perturbed by CO2are reported. Pressure-broadening parameters were measured at a low pressure of CO2(0–180 Torr). At high pressure, the two lines of the doublet broaden as the pressure is increased, but with a markedly lower rate than at low pressure, until they overlap. Such an effect is due to collision cross-section relaxation between the two lines of the inversion components of the doublet. Detailed modeling of the spectral lines permits us to determine pressure-broadening coefficients for 41 transitions, and cross-relaxation parameters for 10 doublets. The results show a decrease of the pressure-broadening parameters with theJquantum number. We compared our results with other previous measurements obtained in the far-infrared and ν2regions, and for several foreign gases such as He, H2, and N2.