Vibrational relaxation in OCS mixtures. Part 1. - Measured relaxation times for pure OCS and for OCS in mixtures with helium-4, helium-3, normal deuterium, ortho-deuterium, HD, normal hydrogen and para-hydrogen

This paper reports experimental measurements of vibrational relaxation times which may be used to show whether there is near resonant vibration-rotation energy transfer between OCS and H₂, D₂ or HD. Vibrational relaxation times have been measured in OCS and OCS mixtures over the temperature range 360 to 1000 K using a shock tube and a laser schlieren system. The effectiveness of the additives in reducing the relaxation time of OCS is in the order ⁴HE < ³HE < D ₂ < H₂ and HD. Along this series the effect of an increase in temperature changes from the case of speeding up the rate with ⁴He to retarding it with D₂, HD and H₂. There is no measurable difference in the effectiveness of n-D₂ and o-D ₂ and little, or no, difference between n-H₂ and p-H ₂. Thus the experimental results do not give clear evidence for rotation-vibration energy transfer between hydrogen and OCS. This contrasts with the situation for CO₂ + H₂ mixtures.