DIRECT MEASUREMENT OF VELOCITY-CHANGING COLLISION CROSS-SECTIONS BY LASER OPTICAL-PUMPING

We extend the theory of velocity-selective laser optical pumping in at omic vapors, allowing for arbitrarily rapid velocity-changing collisio nal rates. The results yield a simple relationship between the line-sh ape areas of narrow spectroscopic features present in optically pumped samples. This relationship gives directly the ground- and excited-sta te velocity-changing collision rates and cross sections. We use the re sults to analyze the data from a laser optical-pumping experiment in L i-6 vapor perturbed by Ar buffer gas.