Time and Intensity Dependence of the Infrared Absorption of SF₆: Measurements with an Injection-Locked Single Mode TEA CO₂ Laser

Abstract

With SF₆ established as the model polyatomic molecule for studies of absorption of high power infrared laser radiation it is surprising that few measurements of the time-development of absorption during a laser Dulse have been made. Those published refer1–4 to intensities between 10-10⁴ W/cm², Rabi flop times > 10 ns and time resolution ~10 ns, where coherent effects, such as selfinduced transparancy and pulse delay, can be observed for transitions essentially between 2 levels. Time-integrated absorption has been reported, e.g. ^5-8 fluences, ø from 1 mJ/cm² − 10 J/cm² (3 KW/cm² − 30 MW/cm²). For most excitation frequencies the absorption cross section, σ, falls as ø^-1/3 from ~ 10^-18 − 10^-19 cm². These values are in contrast to the low intensity value which is as high as 1.7 ß 10^-17 cm².⁵