A low temperature investigation of the N(²D) + CH₄, C₂H₆ and C₃H₈ reactions

Abstract

Low temperature rate constants for the N(2D) + C2H6, C3H8 reactions are shown to be much smaller than previously thought.

A kinetic study of the N(2D) + C2H4 reaction at low temperature

“…36,37 Modifications to the original design have allowed us to implement a detection method based on tunable narrowband radiation in the vacuum ultraviolet (VUV) wavelength range; a region where many strong electronic transitions of atomic radicals are located. In this way, it has been possible to follow the kinetics of both ground (C( 3 P), [38][39][40] H( 2 S) 38,[40][41][42][43][44][45][46][47][48][49] and D( 2 S), 40,49,50 ) and excited (O( 1 D) 45,48,[51][52][53][54][55] and N( 2 D) 56,22,23 ) state atoms at low temperature. As the electronic quenching of N( 2 D) is slow with both Ar 57 and N2, 14 both of these could be used as Laval nozzle carrier gases.…”

“…31,33 Recent updates to the reactions of N( 2 D) with saturated and unsaturated hydrocarbons are treated elsewhere. 22,23 Here, we have also introduced new product channels for the N( expression k(T) = a(T/300) b e -g/T ). The second set of simulations, which corresponds to our nominal model, replaced the rate constant values by a temperature independent value of 8.1 ´ 10 -11 cm 3 s -1 (see Table S1).…”

“…Nunez-Reyez et al 22 examined the reactivity of N( 2 D) with saturated hydrocarbon molecules over the 75-296 K temperature range. Measured rate constants for the N( 2 D) + CH4 reaction were seen to agree with earlier work over the 223-293 K range, [15][16][17]19 thereby validating the values recommended by Herron 9 and Dutuit et al 10 In contrast, the recommended rate constants for the N( 2 D) + C2H6 and C3H8 reactions, based on room temperature experiments, were found to be significantly larger than the rate constants measured by Nunez-Reyes et al 22 at temperatures relevant to Titan's atmosphere. These authors showed that both of these reactions are less efficient as the temperature falls, becoming negligibly important to Titan's photochemistry.…”

“…Extrapolation of the Takayanagi et al 21 results to temperatures relevant to Titan's atmosphere (170 K) predicted a rate constant more than 3 times lower than the Nunez-Reyes et al 23 result. When the Nunez-Reyes et al 23 The studies of Nunez-Reyes et al 22,23 show a clear need for additional measurements of N( 2 D) reactions with other abundant unsaturated hydrocarbons species such as C2H4. The kinetics of the N( 2 D) + C2H4 reaction have been previously studied at room temperature 15,16,20 and from 230 -292 K by Sato et al, 24 who obtained rate constants that decrease to low temperature.…”

Rate constants for the N(2D) + C2H2 reaction over the 50–296 K temperature range

“…While there are several previous dynamical investigations of these reactions, providing detailed information on the preferred product channels, [16][17][18][19][20][21] kinetic studies are sparse, particularly as a function of temperature. Nunez-Reyez et al 22 recently studied the kinetics of the N( 2 D) + CH4, C2H6 and C3H8 reactions over the 75-296 K temperature range. The new results for the N( 2 D) + CH4 reaction were in good agreement with earlier work over the 223-293 K range, [6][7][8]10 thereby validating the rate constants recommended by Herron.…”