We present experimental data showing the first observation of large enhancement of four-wave mixing signals due to velocity-changing collisions. The results are explained with a simple model which describes the population distributions in the presence of velocity-changing collisions and optical pumping, allowing relative velocity-changing collision rates to be inferred from the data.

• Received 28 June 1982

DOI:https://doi.org/10.1103/PhysRevA.27.1217