Kinetic study of electronically metastable nitrogen atoms, N(2 2DJ), by electron spin resonance absorption

Abstract

A kinetic study of electronically metastable nitrogen atoms, N(2 2Dj), is presented. Metastable nitrogen atoms are produced by microwave discharge of N2 diluted in He in a fast flow system. The concentration of N(2D5/2i3/2) is monitored by using electron spin resonance spectroscopy. Deactivation rate constants are reported for N(í)j) with the gases N20,

CRITICAL REVIEW OF N, N + , N + 2 , N ++ , And N ++ 2 MAIN PRODUCTION PROCESSES AND REACTIONS OF RELEVANCE TO TITAN'S ATMOSPHERE

“…PR-RA (Sugawara et al 1980) N ( 2 P ) + N 2 298 4 × 10 −16 PR-RA (Umemoto et al 1985) N ( 2 P ) + N 2 298 3.3 × 10 −17 Compilation (Herron 1999) N ( 2 D) + H 2 298 5 × 10 −12 FP-CL N ( 2 D) + H 2 298 1.7 × 10 −12 FP-RA (Husain et al 1972) N ( 2 D) + H 2 298 2.1 × 10 −12 FP-RS (Husain et al 1974) N ( 2 D) + H 2 298 2.7 × 10 −12 FP-CL (Black et al 1975) N ( 2 D) + H 2 298 3.5 × 10 −12 DF-ESR (Fell et al 1981) N ( 2 D) + H 2 298 2.3 × 10 −12 DF-RF (Piper et al 1987 (Husain et al 1972) N ( 2 P ) + H 2 298 1.9 × 10 −15 FP-RA (Husain et al 1974) N ( 2 P ) + H 2 298 8 × 10 −16 DF-ES (Young & Dunn 1975) N ( 2 P ) + H 2 298 1.4 × 10 −14 PR-RA (Umemoto et al 1985) N ( 2 P ) + H 2 213-300 1.4 × 10 −14a PR-RA (Suzuki et al 1993b) N ( 2 P ) + H 2 298 1.9 × 10 −15 Compilation (Herron 1999) N ( 2 D) + CH 4 298 3 × 10 −12 FP-CL N ( 2 D) + CH 4 298 4.6 × 10 −12 DF-ESR (Fell et al 1981 (Fell et al 1981) N ( 2 D) + C 2 H 6 298 2.1 × 10 −11 LP-LIF (Umemoto et al 1998b) N ( 2 D) + C 2 H 6 298 1.9 × 10 −11 Compilation (Herron 1999) N ( 2 P ) + C 2 H 6 298 5.4 × 10 −13 FP-CL (Umemoto et al 1985) N ( 2 D) + C 3 H 8 298 4.6 × 10 −11 DF-ESR (Fell et al 1981 …”

“…Since the collisional deactivation of N ( 2 D) by N 2 is a slow process, the reaction of N ( 2 D) with methane has been soon recognized as an important pathway. The rate constant at 298 K recommended by Herron (4.0 × 10 −12 cm 3 s −1 ) is the average of the values determined by Fell et al (1981), Umemoto et al (1998b) and Takayanagi et al (1999) (see Table 3). The data by Black et al (1969) were disregarded as they differ too much with respect to the other measurements.…”

“…Both Umemoto et al (1985) and Takayanagi et al (1999) (±25%) for C 2 H 2 k = 6.25 × 10 −11 cm 3 s −1 (±25%) for C 2 D 2 . The rate constant has been measured by two groups (Fell et al 1981;Takayanagi et al 1998b; see Table 3) measured the rate constants over the temperature range 223-293 K and reported values of k = 1.6 × 10 −10 exp (−270/T) cm 3 s −1 and 1.4 × 10 −10 exp(−240/T) for C 2 H 2 and C 2 D 2 , respectively. So the H/D isotope effect was found to be very small.…”

“…The kinetic of the N ( 2 D) + C 2 H 6 reaction has been investigated by two groups (Fell et al 1981;Umemoto et al 1998b) and the room temperature value recommended by Herron is 1.9 × 10 −11 cm 3 s −1 (see Table 3). Considering the rate constant value at room temperature and by comparison with the reactions with other hydrocarbons, there is almost no doubt that this reaction has a small barrier (few hundreds of Kelvin).…”

“…So N ( 2 P) seems to be mainly quenched in collisions with saturated hydrocarbons, whereas the reaction of N ( 2 P) with unsaturated hydrocarbons, such as C 2 H 2 and C 2 H 4 , leads to chemical reactions. (Fell et al 1981;Umemoto et al 1998b; see Table 3). The room temperature value recommended by Herron is 2.9 × 10 −11 cm 3 s −1 .…”