On the rate coefficient of the N(²D)+O₂→NO+O reaction in the terrestrial thermosphere

Abstract

[1] The temperature dependence of the rate coefficient of the N( 2 D)+O 2 !NO+O reaction has been determined using ab initio potential energy surfaces (PES) and classical dynamics. The calculation agrees with the recommended rate coefficient at 300 K ($110 km altitude). The rate coefficient is given by the expression k(T) = 6.2 Â 10 À12 (T/ 300) cm 3 /s/molec. In contrast to the nearly temperatureindependent value of this rate coefficient previously recommended, the value given here increases by almost a factor of about four as the altitude increases from 110 to 200 km. It is also shown that even though N( 2 D) atoms in the thermosphere are produced with large translational energies, using the value of the rate coefficient at the local temperature introduces negligible error in the amount of NO produced. The new value of this rate coefficient will significantly increase the amount of NO computed in the aeronomic models causing a re-evaluation of the heat budget and temperature and density structure of the thermosphere. In particular, implications of the larger rate coefficient for the recent observations of dramatically enhanced 5.3 mm emission from NO in the thermosphere due to solar storms are discussed.

Influence of Atmospheric Solar Radiation Absorption on Photodestruction of Ions at D-Region Altitudes of the Ionosphere

“…The reaction rate coefficients recommended by Sander et al (2011) are used in the model, except for reactions 1-3, 10, 11, 15, 26, 31, 34, 49, 50, and 55-67 of Table 3 where rate coefficients are taken from Smith and Robertson (2008), Lin and Leu (1982), Kalogerakis et al (2009), Fischer and Tachiev (2004), Baulch et al (2005, Altinay and Macdonald (2014), Lafferty et al (1998), Smith and Newnham (2000), Nair andYee (2009), Atkinson et al (2003), Duff et al (2003), Li et al (2014), Herron (1999), Homayoon et al (2014), Fell et al (1990, Butler and Zeippen (1984), Alecu and Marshall (2014), Mellouki et al (1981), Wine et al (1981), and Gierczak et al (2004). It should be noted that the low-pressure-limiting rate coefficients are presented in Table 3 for termolecular association reactions 1 -3, 7, 12, 27, 41, 42, and 47-50 marked by asterisks.…”

Predicting global average thermospheric temperature changes resulting from auroral heating

“…During disturbed periods, the Joule heating is a larger source of energy than particle precipitation [Richmond et al, 1990;Lu et al, 1995;Anderson et al, 1998; [5] Solar radiation, auroral particle precipitation, and Joule heating also affect the chemistry of the thermosphere, most notably by enhancing the level of nitric oxide (NO) in the lower thermosphere. It is known that NO is an efficient radiative cooler for the thermosphere [Sharma et al, 1996;Duff et al, 2003], and it has been postulated that this radiative cooling acts as a "natural thermostat" in mitigating the effects of intense solar disturbances on the atmosphere [Mlynczak et al, 2005]. The reaction between atomic nitrogen and molecular oxygen that produces NO is strongly dependent on temperature [Bailey et al, 2002].…”

Mechanisms leading to NLTE IR emission in the terrestrial thermosphere and their impact on remote sensing of atmospheric parameters

“…16 Since the maximum atmospheric temperature even under very high solar activity is less than 2,000 K, 17 the maximum rotational temperature of NO(v′=1) produced by the inelastic encounters with O is therefore always less than 1500 K and under most circumstances it is less than 1,000 K. Rotational distributions of the (v′=1→v″=0) emission from the chemiluminescent NO resulting from the reaction with O 2 of the ground state N( 4 S) and metastable N( 2 D) atoms may also be described by Maxwell-Boltzmann functions with rotational temperatures about 5,000 and 10,000 K, respectively (Figures 1 and 2). Rate coefficients in Figure 1 are from Duff et al 12 and in Figure 2 are from Duff et al 15 The calculations which form the basis of Figure 1 are supported by the observations of the space shuttle experiment CIRRIS-1A 6,18 while those forming the basis of Figure 2 are supported by the laboratory measurements. 13,14 It should now be recalled that while the rate coefficients in Figure 1 are a few times 10 -13 (cm 3 /molec) and those in Figure 2 are few times 10 -14 (cm 3 /molec), those for the O atom inelastic process are a few times 10 -11 (cm 3 /molec); the rate coefficient for the production of NO(v=1) by the inelastic process is about two orders of magnitude larger than that by reactive processes.…”

“…12,14 Next we integrate the spectrally resolved emission from a vibration-rotation band with high enough vibrational quantum number so that the N( 4 S)+O 2 reaction with smaller exoergicity makes negligible contribution to it and all the intensity is due to the N( 2 D)+O 2 reaction; for example (v′=8→v″=7) will do. Knowing the variation of intensities as function of vibrational level, from calculations 15 and experiments, 14 we then calculate the emission from v′=2 due to N( 2 D)+O 2 and subtract it from total 2→1 vibrational band emission obtaining the contribution of the N( 4 S)+O 2 reaction. The ratio of the two emissions together with the relevant rate coefficients from Figures 1 and 2 gives us the ratio of the two N atom densities.…”

“…This reaction is exothermic by 3.76 eV and produces NO in highly excited rotational and vibrational levels[13][14][15] (Figure 2) 4…”