Theoretical and experimental investigations of rate coefficients of O(¹D) + CH₄ at low temperature

Abstract

The rate coefficients of the barrierless O(D) + CH reaction are determined both theoretically and experimentally at 50-296 K. For the calculations, ring polymer molecular dynamics (RPMD) simulations are performed on the basis of a new neural network potential energy surface (PES) in the reactant asymptotic part. Only the reactant asymptotic part of the PES is constructed because of its barrierless and exothermic properties. Experimentally, the reaction rate coefficients are measured using a supersonic flow reactor. Pulsed laser photolysis of O molecules is used as the source of O(D) atoms, which are detected directly through vacuum ultraviolet laser induced fluorescence at 115 nm. The branching ratio for H atom production is measured by comparing the H atom yields of the O(D) + CH and O(D) + H reactions. At T ≥ 75 K, good agreement between theoretical and experimental rate coefficients is found, while at 50 K, the larger difference is discussed in detail.

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

“…Nevertheless, the flow velocity (73 cm s À1 ) was still high enough to ensure that the gas in the probe region was always replenished between laser shots. O( 1 D) atoms were generated in an identical manner to our other recent studies of O( 1 D) reactivity 16,75,85 through the pulsed laser photolysis of ozone (O 3 ) at 266 nm with an energy of B23 mJ. O( 1 D) atoms were detected through resonant pulsed vacuum ultraviolet laser induced fluorescence (VUV LIF) at 115.215 nm via the O( 1 D) 3s 1 D-2p 1 D transition.…”

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 and H-Atom Product Yields for the Reactions of O(1D) Atoms with Ethane and Acetylene from 50 to 296 K

“…Where the maximum time, ABC , is given by In previous work, 13 we used fits of the type given by expression 10 Taylor series expansion ( &C ≈ 1 − ) as the product -(;) ABC is small, so that plots of ABC against ABC for the target and reference reaction yield straight lines as shown in Figure 5. Finally, the branching ratios can be extracted from the ratio of the slopes of the two plots.…”

“…The reactions of atomic oxygen in its first excited state 1 D, with hydrocarbons have been extensively studied given their importance in atmospheric and combustion chemistry [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] .…”