We apply the formalism presented in a previous paper to calculate spectra of an isolated line
with speed-dependent broadening. The translational motion is modeled on a rigid-sphere
interaction and includes the effect of the mass of the perturber on the profile. We show that
the density, the mass of the perturber, and the ratio of the optical to kinetic cross section all
play a role in revealing or concealing (in the profile) the effects of broadening, which depend
upon the speed of the active molecule.

In this paper, we present a formalism for the exact calculation of spectral profile of an
isolated line undergoing speed-dependent collisional broadening and shifting and Dicke
narrowing. It is couched in the language of the density matrix as in the closely related fields
of transport phenomena, laser physics, and nonlinear optics. The formalism is ab intio in
spirit, permitting the calculation of the line shape starting only from a given interaction
potential. The line shape is obtained by solving a transport/relaxation equation for the off …