The product state-resolved dynamics of the reaction H + N2O → OH(v′,j′) + N2

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The product state-resolved dynamics of the photon-initiated reaction HϩN 2 O→OH ϫ( 2 ⌸ 3/2 ,vЈ,NЈ)ϩN 2 has been studied using Doppler-resolved laser induced fluorescence ͑LIF͒ at a mean collision energy of 143 kJ mol Ϫ1 ͑ϵ1.48 eV͒. Nascent OH(vЈϭ0,1) rovibrational population measurements indicate that only a small fraction of the available energy is channeled into the internal modes of the OH reaction products, as is consistent with previous work at other collision energies. State-resolved angular scattering distributions have been determined and are found to depend sensitively on product OH rovibrational quantum state. For the vЈϭ0 products, the angular scattering distributions are forward-backward peaking at low NЈ, changing to sideways peaking at high NЈ. OH products born in the vЈϭ1,NЈϭ6 state possess forward-backward peaking angular scattering distributions, similar to the OH(vЈϭ0) products born with intermediate NЈ. In addition to these findings, the experiments have allowed the precise determination of the OH quantum state-resolved distributions of kinetic energy releases and, hence, by energy balance, of internal energies accessed in the N 2 co-products. The product state-resolved kinetic energy disposals are found to broaden somewhat, and to favor higher kinetic energy disposal, as the internal energy of the OH is increased. The internal energies accessed in the OH and N 2 products are therefore ͑anti-͒correlated. More interestingly, the kinetic energy distributions are bimodal, particularly for OH(vЈϭ0) fragments born in high NЈ, and for those born in vЈϭ1. This finding is attributed to the operation of two microscopic reaction mechanisms, which are probably associated with H atom attack at the two ends of the NNO target molecule. The results are discussed in the light of previous experimental and theoretical work.

Section: Introductionmentioning

confidence: 99%

The H+N2O→OH(2Π3/2,v′,N′)+N2 reaction at 1.5 eV: New evidence for two microscopic mechanisms

Brouard

Burak

Gatenby

et al. 1999

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“…18 Indeed their energy distributions peaked at around twice the estimates reported earlier, 23,24 which were based upon direct LIF measurements of the scattered CO ͑necessarily, averaged over the quantum state distribution in the scattered OH͒. Comparisons between the dynamical behavior of reaction ͑1͒ and of the related, but strongly exothermic, reaction that follows: [25][26][27][28] suggest the possibility that the ''missing'' population might be associated with CO molecules scattered into highly excited rotational levels, that remained undetected in the LIF experiments. 18 The product rotational angular momentum distributions, both scalar and vectorial, reflect the stereodynamics of the collisions that produce them-the prime focus of the present investigation.…”

Section: Introductionmentioning

confidence: 74%

“…In the case of the HNNO system, reaction at 1.5 eV is believed to involve H atom attack at the terminal nitrogen atom end of NNO, and to proceed to OH and N 2 products via an H-atom migration mechanism. [25][26][27][28] In that case, torsional forces would have to operate after passage through the ͑planar͒ transition state 40 associated with H-atom migration. 28 For the HϩCO 2 reaction, a similar, high energy H-atom migratory mechanism might also be involved, 31 although it may not be necessary to invoke its participation in order to explain the polarization data.…”

Section: Resultsmentioning

confidence: 99%

Product state resolved stereodynamics: Rotational polarization of OH(2Π;υ′,N′,Ω,f ) scattered from the reaction, H+CO2→OH+CO

Brouard

Burak

Hughes

et al. 2000

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“…7 In the case of reactions of polyatomic molecules, the available dynamical information is sparse, but nonadiabatic transitions to low-lying excited electronic states separated from the ground adiabatic state by SO interactions have been reported for a few reactions of triatomic and larger molecules. [8][9][10][11][12][13][14] We recently reported nonadiabatic production of SO excited Cl͑ 2 P 1/2 ͒ atoms ͑henceforth denoted as Cl * ͒ in the reaction CH 3 + HCl → CH 4 + Cl͑ 2 P J ͒ ͑ 1͒…”

Section: Introductionmentioning

confidence: 99%

Adiabatic and nonadiabatic dynamics in the CH3(CD3)+HCl reaction

Retail

Pearce

Greaves

et al. 2008

The scattering dynamics leading to the formation of Cl ͑ 2 P 3/2 ͒ and Cl * ͑ 2 P 1/2 ͒ products of the CH 3 + HCl reaction ͑at a mean collision energy ͗E coll ͘ = 22.3 kcal mol −1 ͒ and the Cl ͑ 2 P 3/2 ͒ products of the CD 3 + HCl reaction ͑at ͗E coll ͘ = 19.4 kcal mol −1 ͒ have been investigated by using photodissociation of CH 3 I and CD 3 I as sources of translationally hot methyl radicals and velocity map imaging of the Cl atom products. Image analysis with a Legendre moment fitting procedure demonstrates that, in all three reactions, the Cl/ Cl * products are mostly forward scattered with respect to the HCl in the center-of-mass ͑c.m.͒ frame but with a backward scattered component. The distributions of the fraction of the available energy released as translation peak at f t = 0.31-0.33 for all the reactions, with average values that lie in the range ͗f t ͘ = 0.42-0.47. The detailed analysis indicates the importance of collision energy in facilitating the nonadiabatic transitions that lead to Cl * production. The similarities between the c.m.-frame scattering and kinetic energy release distributions for Cl and Cl * channels suggest that the nonadiabatic transitions to a low-lying excited potential energy surface ͑PES͒ correlating to Cl * products occur after passage through the transition state region on the ground-state PES. Branching fractions for Cl * are determined to be 0.14Ϯ 0.02 for the CH 3 + HCl reaction and 0.20Ϯ 0.03 for the CD 3 + HCl reaction. The difference cannot be accounted for by changes in collision energy, mass effects, or vibrational excitation of the photolytically generated methyl radical reagents and instead suggests that the low-frequency bending modes of the CD 3 H or CH 4 coproduct are important mediators of the nonadiabatic couplings occurring in this reaction system.