Abstract

Both the soft and hard collision models of lineshape require a knowledge of the bulk diffusion coefficient of the gas. The experimentally measured lineshapes were empirically fit to both models to obtain what is known as an “optical” diffusion coefficient. It has been found that at low densities, where the Doppler effect is the dominant broadening mechanism, there is good agreement between the “optical” and bulk diffusion coefficients. However as the density is increased, the optical diffusion coefficient is up to 300 lower than expected. It is felt that this effect can more simply be explained by a slight deviation in the pressure broadening mechanism from a simple exponential decay of dipole correlation. Evidence supporting this conclusion will be presented.

© 1993 Optical Society of America