Retrieval of the nighttime thermospheric temperature from NO(v=1) 5.3-μm infrared emission

Abstract

Classical trajectory calculations have been performed to determine the rotational distribution of vibrationally excited nitric oxide from collisions with atomic oxygen. The reaction occurs on two electronic potential energy surfaces which must be considered for a realistic description of the O+NO collision dynamics. The results, which have been statistically averaged over both electronic potential energy surfaces, are in good agreement with the available experimental data for vibrational relaxation of NO(v less than or equal to 9), as well as the temperature dependence of NO(v equals 1). The state-to-state relaxation rate coefficients involve the formation of long-lived collision complexes and indicate statistical behavior in O+NO collisions. The present study confirms earlier analysis that the NO(v equals 1) rotational distributions can indeed by described by a Maxwell-Boltzmann distribution, albeit with a rotational temperature of approximately 75% of the initial translational temperature. Thus, it appears possible to establish a lower bound to, and an estimate of, the nighttime quiescent terrestrial thermosphere by measuring the rotational envelope of the 5.3 micrometer emission from NO.