The vibrational relaxation time of nitric oxide in NOsngbnd;Ar mixtures was determined over the temperature range 1500deg;mdash;7000deg;K. An ultraviolet absorption technique using 1270hyphen;A radiation was employed to monitor the vibrational temperature as a function of time after these mixtures were shock heated to high translational temperatures.P10, the transition probability per oscillator per collision for transition between vibrational levels 1 and 0 calculated from the measured relaxation times ranged from 1.0times;10mdash;3at 1500deg;K to 2.8times;10mdash;2at 7000deg;K for NOsngbnd;NO collisions. Argon is about 1/50 as efficient as NO. The results are compared with the lower temperature (400deg;mdash;1500deg;K) work of Robben and with the adiabatic theory of Schwartz, Slawsky, and Herzfeld and the nonadiabatic theory of Nikitin.
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