Nitrogen broadening and shift coefficients in the 4.2–4.5-μm bands of CO2

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 ν3 band of 13C16O2. N2 broadening and shift coefficients of ν312C16O2 transitions were also measured. In addition, nitrogen-broadening coefficients for many transitions in the ν3+ν2−ν2 hot band of 13C16O2 as well as the ν3 band of 13C16O18O were also determined. The results were obtained by analyzing five high-resolution (0.0028cm−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 4.08cm sample cell, total pressures up to 470Torr, and a 90% 13C-enriched CO2 sample. For the pressure-broadened spectra the 13C16O2 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 0.0643cm−1atm−1 at 296K. The measured shift coefficients were all negative and varied between 0 and −0.0036cm−1atm−1. The results obtained are compared with other values reported in the literature.