Strengths and air-broadened widths of H 2O lines in the 2950–3400 cm -1 region

Abstract

Measurements of the strengths and air-broadened widths of 223 lines of water vapor have been made with high resolution in the region 2950–3400 cm -1. The strength data of the lines in the 2ν 2 and ν 1 bands are analyzed to determine the band strengths and the coefficients of the F factors. The band strengths of the 2ν 2 and ν 1 bands were found to be 1.75±0.08 and 10.3±1.1 cm -2 atm -1 at 296 K, respectively. The selection rules of the lines observed in the ν 3 band are forbidden in the symmetric-rotor limit. The majority of the measured strengths of these lines differ from the calculated values because of different asymmetries in the upper and lower vibrational states. Also, Coriolis perturbations in several lines of the ν 1 and ν 3 bands were observed in the strength measurements. The direct method was applied to determine the air-broadened line widths. The results are compared to the computed values of Benedict and Kaplan. There is good agreement between this work and the computed results for line width values greater than 0.05 cm -1 atm -1. However, for line widths less than 0.05 cm -1 atm -1, the measured values are smaller than the computed widths. A value of 0.018 cm -1 atm -1 is given for the width of the line at 3378.071 cm -1, whereas the calculated value is 0.032 cm -1 atm.