Hot band rotational relaxation time in carbonyl sulfide by transient infrared–microwave double resonance

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Abstract
Rotational relaxation time (T) has been measured for pure carbonyl sulfide (16O 12C 32S) in a highly vibrationally and rotationally excited state (031f0, J = 24). A pulsed CO2 laser [P9(24)] line was used to excite the OCS gas: (011f0, J = 25) → (031f0, J = 24). The transient population difference between l-doublet states (031f0, J = 24) and (031e0, J = 24), was monitored with a microwave (7.4 GHz) probe signal. For pressures 5–40 Pa, individual transient infrared–microwave signals were analyzed via a least squares fit. From the gain pulse shape, it is determined that population decay time (T1) and polarization decay time (T2) were equal within a factor of 2. From the pressure dependence of T, it is concluded that (pT) = 3.64±0.5 μs Pa = 27.3±4 ns Torr.