Elastic velocity-changing collisions have been observed for the first time to our knowledge in a nonpolar molecule by photon-echo studies of SF6 using a frequency-switched CO2 laser that we have developed. The photon-echo decay is nonexponential and reveals the velocity-changing collision cross section to be σvc = 180 Å2, with an average velocity change per collision of Δu = 155 cm/sec. Using delayed optical nutation, we also determine the cross section for the population decay rate (1/T1) to be σpop = 335 Å2. To within experimental accuracy, we find that phase-interrupting collisions are not important (T1 ≃ T2). A comparison of these cross sections with those for the polar molecule 13CH3F is made.
© 1981 Optical Society of America
Original Manuscript: October 3, 1980
Published: January 1, 1981
B. Comaskey, R. E. Scotti, and R. L. Shoemaker, "Optical coherent transient measurements of velocity-changing collisions in SF6," Opt. Lett. 6, 45-47 (1981)