Production processes of H(D) atoms in the reactions of NO(Σ) with C2H2, C2H4, H2O, and their isotopic variants

Reactive quenching of NO (A2Σ+) with H2O leads to HONO: a theoretical analysis of the reactive and nonreactive electronic quenching mechanisms

“…10 will result in cleavage of an O-H bond of H 2 O, producing a free H-atom as previously observed in experiments by Umemoto and co-workers. 25 As discussed above, there is an energetic driving force on D 2 for decreasing R ON at elongated r OH A . This supports the formation of HONO as the co-product in the reactive electronic quenching pathway.…”

“…Turning to the reactive electronic quenching pathway, Umemoto and co-workers experimentally probed the production of H atoms from collisions of NO (A 2 S + ) with H 2 O, C 2 H 2 , and C 2 H 4 . 25 In their experiments, a pump pulse excited the NO A 2 S + ' X 2 P band while a probe pulse monitored the formation of H-atoms via excitation to the 2 2 S state. The electronically 27 Analysis of these spectra, along with electronic structure calculations performed at the B3LYP/6-311++G(2d,2p) level of theory, indicated that the most stable NO + H 2 O complex geometry involves the nitrogen atom of NO hydrogen-bonding with H 2 O. Salmi and co-workers obtained optimized geometries for NO + H 2 O in both its 2 A 0 and 2 A 0 0 states (D 0 and D 1 ) at the CCSD(T)/A 0 VQZ level of theory.…”

Branching ratios for quenching of nitric oxide A2Σ+(ν′ = 0) to X2Π(ν″ = 0)

“…Unlike reaction 5.11, however, the reactive quenching pathway for O 2 results in the consumption of NO and cannot contribute to groundstate recovery. Umemoto et al 60 observed fast H atoms produced by quenching of NO A 2 S + (n 0 = 0) by H 2 O. The authors predicted that quenching proceeds through a very efficient nonadiabatic transition to the lowest 2 A 0 state of the NO(X 2 P) + H 2 O(X 1 A 1 ) system, which adiabatically correlates with H( 2 S) + HONO( 1 A 0 ) as well as the NO(X 2 P) + H 2 O(X 1 A 1 ) products.…”

“…The absolute H( 2 S) yield was not determined in ref. 60, however, and the relative importance of the reactive pathway remains unknown.…”

Selective production and kinetic analysis of thermally equilibrated N2(B3Πg, v = 0) and N2(W3Δu, v = 0)

“…The procedure to detect H atoms was the same as that described previously. 5,6,[30][31][32] Ground-state H atoms were excited to the 2 2 S state, using the two-photon scheme at 243.2 nm. These excited H atoms were collisionally relaxed to the nearby 2 2 P J states, which fluoresce vacuum ultraviolet light at 121.6 nm, Lyman a.…”