Halfwidths and line shifts of water vapor broadened by CO2: Measurements and complex Robert-Bonamy formalism calculations

Measurements of CO2-broadened line shifts of 29 transitions belonging to the vl, 2 nu(2) and nu(3) bands of water vapor are made at T = 294.4 K. The halfwidths of 31 transitions were previously reported [R. R. Gamache et al (1995)]. Calculations of the halfwidth and line shifts based on a fully complex implementation of the formalism of Robert and Bonamy are made for these transitions. The calculations employ an electrostatic, Lennard-Jones (6-12) atom-atom, and isotropic induction and dispersion components of the potential and dynamics correct to second order in time. The results are compared with the measured values and very good agreement is observed for both halfwidths and line shifts. A new feature in this approach is that the real and imaginary components of the S matrix affect both the halfwidth and the line shift. It is shown here that the imaginary parts of the S matrix strongly affect the calculated H2O-CO2 halfwidths. (C) 1997 Elsevier Science Ltd.