Nitrogen broadening and shift coefficients in the 4.2–4.5-μm bands of CO 2

Abstract

In this study we report the first high-resolution measurements of pressure broadening and pressure-induced shift coefficients due to nitrogen for rovibrational transitions in the ν 3 band of 13 C 16 O 2 . N 2 broadening and shift coefficients of ν 3 12 C 16 O 2 transitions were also measured. In addition, nitrogen-broadening coefficients for many transitions in the ν 3+ ν 2− ν 2 hot band of 13 C 16 O 2 as well as the ν 3 band of 13 C 16 O 18 O were also determined. The results were obtained by analyzing five high-resolution ( 0.0028 cm −1 ) room temperature laboratory absorption spectra with a multispectrum nonlinear least-squares spectral fitting technique. The data were recorded with the McMath-Pierce Fourier transform spectrometer of the National Solar Observatory on Kitt Peak using a 4.08 cm sample cell, total pressures up to 470 Torr , and a 90% 13 C -enriched CO 2 sample. For the pressure-broadened spectra the 13 C 16 O 2 volume-mixing ratios were⩽0.5%. Similar to broadening coefficients, the measured pressure shift coefficients were also found to be transition dependent. However, the shift coefficients were different in the P and R branch lines with the same rotational quantum number, J. The measured nitrogen-broadening coefficients range from 0.0960 to 0.0643 cm −1 atm −1 at 296 K . The measured shift coefficients were all negative and varied between 0 and −0.0036 cm −1 atm −1 . The results obtained are compared with other values reported in the literature.