Line-mixing effects in Ar-broadened l-doublets of a hot band of OCS

The spectra of several Ar-broadened symmetric doublets in the hot band ν + ν - ν (at 850 cm) of OC S have been recorded with a tunable diode-laser spectrometer. The pressure-broadening coefficients measured for sufficiently separated lines belonging to 7 doublets are in agreement with the results previously obtained in the ν band. From these data, we have determined, for different pressures of argon, line-coupling coefficients for 15 doublets in the P and R branches of the hot band. These coefficients appear to be small and negative, at the limit of our estimated accuracy, which implies very weak line-mixing effects in the doublets, in agreement with the results of a semiclassical calculation as well as with results of coupling cross sections estimated at large-j values from the infinite order sudden (IOS) approximation.