THEORETICAL LINE SHAPE FOR H2O VAPOR; APPLICATION TO THE CONTINUUM

Abstract

The collision broadened line shape problem is formulated following Van Vleck and Huber in terms of the symmetrized autocorrelation function of the dipole moment operator. The formulation maintains radiation balance between emission and absorption over the full spectral extent of the line and satisfies the generalized Nyquist theorem. The f sum rule and the Kramers-Kronig relationship are considered. The spectral line shape for the impact approximation is obtained and the implications of the approximations are discussed. The impact approximation is shown to be a factor of two above the observed continuum absorption at 1000 cm -1 for self-broadened water case at 296 K. The impact theory is modified to include the effect of the duration of collision time and thus yields a gaussian shape for the form factor in the far line wings. The formulation is shown to be appropriate over the entire spectral region from the microwave to near infrared.