Optical coherent transient measurements of velocity-changing collisions in SF(6).
Elastic velocity-changing collisions have been observed for the first time to our knowledge in a nonpolar molecule by photon-echo studies of SF(6) using a frequency-switched CO(2) laser that we have developed. The photon-echo decay is nonexponential and reveals the velocity-changing collision cross section to be sigma(vc) = 180 A(2), with an average velocity change per collision of Deltau = 155 cm/sec. Using delayed optical nutation, we also determine the cross section for the population decay rate (1/T(1)) to be sigma(pop)=335 A(2). To within experimental accuracy, we find that phaseinterrupting collisions are not important (T(1) approximately T(2)). A comparison of these cross sections with those for the polar molecule (13)CH(3)F is made.
Comaskey
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B
Scotti
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Shoemaker
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RL