Temperature dependence of the quenching of vibrationally excited nitrogen by atomic oxygen

Abstract

A photo-ionization detector for vibrationally excited nitrogen (N2*) has been used to obtain the rate of quenching of N2* by atomic oxygen in the temperature range 300ø-723 øK. The quenching rate coefficient was found to be 3.2 X 10 -•5 cm 3 s -• at 300øK, 1.3 X 10 -•4 cm 3 s -• at 463øK, 2.7 X 10 -•4 cm a s -• at 633øK, and 4.0 X 10 -• cm a s -• at 723øK. These rate coefficients are extremely large compared with the expected values for a conventional vibrational-translational (VT) energy transfer process in this temperature range. They are also large compared with the predictions of the vibrational relaxation theory developed by Fisher and Bauer for the N2-O system based upon crossing of covalent potential energy curves. The measured coefficients combined with higher temperature data obtained elsewhere with different experimental methods indicate that the VT process in the N2-O system is anomalously efficient over the range 300ø-4500øK and has only a moderate temperature dependence. This result has important consequences in the upper atmosphere, where the effect of an efficient VT process involving N2 and O is to hold the atmospheric N2 vibrational temperature at or very near the ambient kinetic temperature, in agreement with the results of recent rocket probe experiments. Processes that produce and quench vibrationally excited nitrogen (N•,) have attracted considerable attention in recent years because of their potential impact on the physics and chemistry of the earth's upper atmosphere. The Ns* is produced at high altitudes by collisions with ionospheric and auroral electrons, in exothermic chemical reactions, and in energy transfer processes involving other excited atmospheric species [Walker et al., 1969]. Once it is produced, the Ns* can transfer energy to infrared-emitting molecules such as COs, CO, and NO that contribute to the airglow. Vibrational excitation has also been found experimentally [Schmehekopfet al., 1968] to accelerate the rate of the reaction of O + with Ns to form NO + , an important ion-molecule reaction in the ionosphere. Until very recently, information on atmospheric production and loss processes involving Ns* has been almost

Stormtime subauroral density troughs: Ion‐molecule kinetics effects

“…The contributions of suprathermal electrons via electronic triplet states and of transport processes are neglected. At altitudes ≥300 km the main quencher of vibrational states is atomic oxygen with the rate coefficient [ McNeal et al , 1974] L O ≃ 10 −10 · exp(−70/ T n 1/3 ) · [ O ] s −1 ([ O ] represents the atomic oxygen density). Accounting for charge transfer yields L V = L O + c V · k 1,0 · n i s −1 .…”

Impact of vibrational excitation on ionospheric parameters and artificial airglow during HF heating in the F region

“…The main quencher of the N 2 vibrational excitation in the ionosphere is atomic oxygen. The rate coefficient of this V‐T process is given by the formula [ McNeal et al , 1974]: …”

Multiple fluorescent scattering of N2 ultraviolet emissions in the atmospheres of the Earth and Titan

“…Waite et al [1979] reexamined the vibrational equilibrium temperature in aurorae and concluded that efficient quenching by O [McNeal et al, 1974] makes it unlikely that N 2 vibrational temperatures are high enough to permit entrapment. ating on higher vibrational levels (v" = 1, 2 .... ) of the ground state or that there is enough vibrationally excited N 2 in the thermosphere to make even those bands optically thick.…”