Dicke narrowing for rigid spheres of arbitrary mass ratio

There is a need in spectral line shapes for a realistic treatment of the translational motion in the case of arbitrary ratio of the mass of the perturber to the mass of the active molecule. Here we use a one-dimensional rigid-sphere collision kernel to determine the translational motion. By discretizing the velocity we are able to exploit the analogy between Dicke narrowing and line mixing. The validity of using a one-dimensional versus three-dimensional kernel is explored. A comparison of the results with the well-known soft and hard collision models is also carried out.