A combined theoretical and experimental investigation of the kinetics and dynamics of the O(¹D) + D₂reaction at low temperature

Abstract

The O(D) + H reaction is a prototype for simple atom-diatom insertion type mechanisms considered to involve deep potential wells. While exact quantum mechanical methods can be applied to describe the dynamics, such calculations are challenging given the numerous bound quantum states involved. Consequently, efforts have been made to develop alternative theoretical strategies to portray accurately the reactive process. Here we report an experimental and theoretical investigation of the O(D) + D reaction over the 50-296 K range. The calculations employ three conceptually different approaches - mean potential phase space theory, the statistical quantum mechanical method and ring polymer molecular dynamics. The calculated rate constants are in excellent agreement over the entire temperature range, exhibiting only weak temperature dependence. The agreement between experiment and theory is also very good, with discrepancies smaller than 26%. Taken together, the present and previous theoretical results validate the hypothesis that long-lived complex formation dominates the reaction dynamics at low temperature.

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.…”

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

“…The measurements reported here were performed using a supersonic flow (Laval nozzle) apparatus, which has been described in previous work. [25][26][27] Later studies report the various modifications applied to the original experiment to allow narrowband tunable vacuum ultraviolet radiation to be generated for the detection of several atomic species in their ground and excited electronic states (C( 3 P), [28][29][30] H( 2 S) 28,[30][31][32][33][34][35][36][37][38] and D( 2 S), 30,39 O( 1 D) 35,38,[40][41][42][43][44] and N( 2 D) 15,22 ). Experiments were performed using argon and nitrogen based Laval nozzles during the present work as N( 2 D) atoms are only slowly quenched by both of these gases.…”

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

“…The experiments performed in this study employed an existing continuous supersonic flow reactor whose main features have been described previously. [28][29][30] Further modifications to the apparatus allowing the generation of narrowband tunable radiation in the vacuum ultraviolet wavelength range for the detection of atomic radicals in ground and excited electronic states are reported in later work (C( 3 P), [31][32][33] H( 2 S) 31,[33][34][35][36][37][38][39][40][41] and D( 2 S), 33,42 O( 1 D), 38,41,[43][44][45][46][47] and N( 2 D)). 6 During this work, both Ar and N2 were used as carrier gases as they result in only slow quenching of N( 2 D) atoms.…”