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

Abstract

The reactions of metastable atomic nitrogen N(2D) are important processes in the gas-phase chemistry of several planetary atmospheres.

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

“…in a similar manner to our earlier study of the N( 2 D) + C2H2 reaction, 23 where atomic carbon was also seen to react with C2H2. Indeed, it can be seen from Reyes et al, 23 as well as the implications for the data analysis procedures.…”

“…The various contributions to the constants . / and 2 / are described in Nunez-Reyes et al, 23 replacing C2H2 by C2H4. In common with this earlier work, a single exponential function of the form…”

“…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.…”

“…Three nozzles were employed during the present experiments allowing four different temperatures to be attained between 50 and 177 K (one nozzle was used with both N2 and Ar in separate experiments). The flow characteristics are summarized in Table 1 of Nunez-Reyes et al 23 The apparatus was also used as a slow-flow reactor to allow measurements to be made at room temperature. N( 2 D) atoms could not be produced by photolysis during this work, due to the scarcity of appropriate precursor molecules.…”

“…Indeed, N( 2 D) atoms formed at these altitudes are relatively unaffected by non-reactive losses due to their long radiative lifetime and the slow electronic quenching of N( 2 D) by N2 at low temperature. 13,14 Previous work on the kinetics [15][16][17][18][19][20][21][22][23][24] and dynamics [25][26][27][28][29][30] of N( 2 D) atom reactions with saturated and unsaturated hydrocarbons indicate that these processes could lead to significant quantities of nitrogen bearing organic molecules. Indeed, several reactions involving N( 2 D) atoms have been identified as potentially key processes in earlier photochemical modeling studies of Titan's atmosphere.…”