Abstract

A pilot study is described in which the resonance of the 10.6-μm CO₂ laser radiation with the ν₃ vibrational level of the SF₆ molecule is used to explore the effect of gas density on the time response of fluorescence. A slow increase of the fluorescent decay time with pressure of pure SF₆ is found that is interpreted in terms of a degree of equilibrium between vibrational and translational temperatures. In SF₆–air mixtures, however, the increase of air pressure from 0 atm to 1 atm produces a proportional increase of the time constant from milliseconds to seconds in a process in which the vibrational–translational relaxation time is very small compared with the bulk cooling time determined by the thermal diffusivity. The results are compared with previous studies using Q-switched pulse excitation.

© 1972 Optical Society of America

Interferometric studies of nonlinear relaxation processes in vibrationally highly excited SF₆ molecules

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