Rate Constants for Quenching and Self-Annihilation of NCl(aΔ)

Abstract

Quenching and self-annihilation rate constants for NCl(a) have been determined using pulsed 248 nm photolysis of ClN 3 to generate the metastable. Previous quenching measurements that employed different sources for NCl(a) yielded dramatically different rate constants. The present study provided quenching rate constants for Cl 2 , HCl, and H 2 that are in good agreement with the discharge flow measurements of Hewett et al. (J. Phys. Chem. A 2000, 104, 539). Determination of the self-annihilation rate constant required knowledge of the branching fraction for NCl(a) formation for 248 nm photolysis of ClN 3 . This information was obtained from time-resolved measurements of NCl(X) formation and decay. A lower bound for the branching fraction of 0.7 was determined. Self-annihilation of NCl(a) was studied by using intense photolysis pulses to generate high concentrations of NCl(a). Analysis of the second-order decay component yielded a rate constant of (7.0 ( 1.5) × 10 -13 cm 3 s -1 . This value is an order of magnitude smaller than the previous estimate (Henshaw et al.

Photofragment translation spectroscopy of ClN3 at 248 nm: Determination of the primary and secondary dissociation pathways

“…In a previous letter we reported that the molecular dissociation channel, that is reaction ͑1͒, converts available energy predominantly into product internal excitation and that the branching ratio between the molecular elimination ͑1͒ and radical bond-rupture ͑2͒ channels was found to be NCl+ N 2 /Cl+N 3 = 0.05± 0.03/ 0.95± 0.03, 4 contrary to previous results that assumed NCl+ N 2 to be the dominant channel. 11 As in the earlier imaging experiments, 1 a bimodal translational energy distribution was reported for the Cl atom in the PTS experiment.…”

“…4 Owing to the non-state-selective detection scheme used in this experiment, identification of the electronic state of the NCl product, i.e., evaluating the relative importance of reactions ͑1a͒ and ͑1b͒, is not possible, although previous studies provided evidence that the spin-allowed reaction ͑1a͒ is more probable than reaction ͑1b͒. 11 Besides reaction ͑1͒, other pathways, including the production of NCl ͑X 3 ⌺͒ via a spin-allowed channel,…”

Photodissociation of ClN3 at 157 nm: Theory suggests a pathway leading to cyclic N3

“…The four known and experimentally identified states, namely, X 1 AЈ͑S 0 ͒, Ã 1 AЉ͑S 1 ͒, B 1 AЈ͑S 2 ͒, and C 1 AЉ͑S 3 ͒, [9][10][11][12][13] nothing is known about the mechanism of how cyclic N 3 is formed by excitation at 157.4 nm. The four known and experimentally identified states, namely, X 1 AЈ͑S 0 ͒, Ã 1 AЉ͑S 1 ͒, B 1 AЈ͑S 2 ͒, and C 1 AЉ͑S 3 ͒, [9][10][11][12][13] nothing is known about the mechanism of how cyclic N 3 is formed by excitation at 157.4 nm.…”

Experimental study on supersonic all gas-phase iodine laser driven by NF3/D2/DCl/CF3I combustion

“…There are at least three ways to produce the energy carrier NCl(a): the thermal decomposition or photo-dissociation of ClN 3 [13][14][15][16][17][18][19], the reaction of HN 3 and Cl atoms [2][3][4][8][9][10][11][12] and the reaction of NCl 3 and H atoms [20][21][22][23][24]. The positive gain and demonstration of lasing at 1315nm have been obtained with the latter two methods to generate NCl(a).…”