Product spin–orbit state resolved dynamics of the H+H2O and H+D2O abstraction reactions

Brouard, M.; Burak, I.; Marinakis, Sarantos; Lago, L. Rubio; Tampkins, P.; Vallance, Claire

doi:10.1063/1.1809578

Cited by 10 publications

(5 citation statements)

References 106 publications

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“…Only 7% and 9% of the available energy went to HD vibration and rotation, respectively. This result is noticeably different from what was found in studies of the isoelectronic H + H 2 O reaction (also for its isotopic counterpart H + D 2 O) at comparable energies, where H 2 (HD) was found to be vibrationally and rotationally more excited in both experiment [38][39][40][41] and theory. 40,42,43 In this study, we record the 2+1 resonance enhanced multiphoton ionization (REMPI) spectra of the nascent CD 3 products that result from the reaction of fast H atoms with CD 4 under single collision conditions.…”

Section: Introductioncontrasting

confidence: 97%

Section: Introductioncontrasting

confidence: 77%

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H + CD₄ Abstraction Reaction Dynamics: Product Energy Partitioning

Lendvay

Troya

et al. 2005

J. Phys. Chem. A

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This paper presents experimental and theoretical studies of the product energy partitioning associated with the H + CD4 (nu = 0) --> HD + CD3 reaction for the collision energy range 0.5-3.0 eV. The theoretical results are based on quasiclassical trajectories from (1) first principles direct dynamics calculations (B3LYP/6-31G), (2) an empirical surface developed by Espinosa-García [J. Chem. Phys. 2002, 116, 10664] (EG), and (3) two semiempirical surfaces (MSINDO and reparametrized MSINDO). We find that most of the energy appears in product translation at energies just above the reactive threshold; however, HD vibration and rotation become quite important at energies above 1 eV, each accounting for over 20% of the available energy above 1.5 eV, according to the B3LYP calculations. The barrier on the B3LYP surface, though being later than that on EG, predicts significantly higher HD vibrational excitation than EG. This deviation is contradictory to what would be expected on the basis of the Polanyi rules and derives from modest differences in the potential energy surfaces. The CD3 internal energy is generally quite low, and we present detailed rotational state distributions which show that the CD3 rotational distribution is largely independent of collision energy in the 0.75-1.95 eV range. The most populated rotational levels are N = 5 and 6 on B3LYP, with most of that excitation being associated with motion about the C2 axes, rather than C3 axis, of the CD3 product, in good agreement with the experimental results. Through our extensive studies in this and previous work concerning the scattering dynamics, we conclude that B3LYP/6-31G provides the best available description of the overall dynamics for the title reaction at relatively high collision energies.

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Section: Introductioncontrasting

confidence: 97%

Section: Introductioncontrasting

confidence: 77%

H + CD₄ Abstraction Reaction Dynamics: Product Energy Partitioning

Lendvay

Troya

et al. 2005

J. Phys. Chem. A

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“…In the H + H 2 O reaction, however, Brouard et al, explained formation of both 2 P 1/2 and 2 P 3/2 components of OH products by SO interactions further out in the exit channel. 7 We note that, by consideration of microscopic reversibility, efficient nonadiabatic couplings far in the exit channel should imply a high propensity for early SO energy transfer in the reverse direction. The observation of fast Cl* quenching by CH 4 reported by Matsumi et al 37 is thus consistent with a picture of nonadiabatic interactions occurring late in the exit channel.…”

Section: Discussionmentioning

confidence: 85%

“…In the case of polyatomic reactions, experimental evidence of such non-BO behaviour is very sparse. Detection of spin-orbit (SO) excited OH and OD products from the reactions of H + N 2 O, 6 H + H 2 O, 7 and F + D 2 O 8 has been assigned as a signature of nonadiabatic couplings between ground and excited PESs occurring after the transition state (TS), either far in the exit channel or in the post-transition state region.…”

Section: Introductionmentioning

confidence: 99%

Imaging the nonadiabatic dynamics of the CH3 + HCl reaction

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Greaves

Pearce

et al. 2007

Phys. Chem. Chem. Phys.

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LAB-frame velocity distributions of Cl-atoms produced in the photoinitiated reaction of CH(3) radicals with HCl have been measured for both the ground Cl ((2)P(3/2)) and excited Cl* ((2)P(1/2)) spin-orbit states using a DC slice velocity-map ion imaging technique. The similarity of these distributions, as well as the average internal excitation of methane co-products for both Cl and Cl* pathways, suggest that all the reactive flux proceeds through the same transition state on the ground potential energy surface (PES) and that the couplings which promote nonadiabatic transitions to the excited PES correlating to Cl* occur later in the exit channel, beyond the TS region. The nature of these couplings is discussed in light of initial vibrational excitation of CH(3) radicals as well as previously reported nonadiabatic reactivity in other polyatomic molecule reactions. Furthermore, the scattering of the reaction products, derived using the photoloc method, suggests that at the high collision energy of our experiment (E(coll) = 22.3 kcal mol(-1)), large impact parameter collisions are favoured with a reduced kinematic constraint on the internal excitation of the methane co-product.

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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 Journal of Chemical Physics

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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.

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Product spin–orbit state resolved dynamics of the H+H2O and H+D2O abstraction reactions

Cited by 10 publications

References 106 publications

H + CD₄ Abstraction Reaction Dynamics: Product Energy Partitioning

H + CD₄ Abstraction Reaction Dynamics: Product Energy Partitioning

Imaging the nonadiabatic dynamics of the CH3 + HCl reaction

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

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Product spin–orbit state resolved dynamics of the H+H2O and H+D2O abstraction reactions

Cited by 10 publications

References 106 publications

H + CD4 Abstraction Reaction Dynamics: Product Energy Partitioning

H + CD4 Abstraction Reaction Dynamics: Product Energy Partitioning

Imaging the nonadiabatic dynamics of the CH3 + HCl reaction

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

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H + CD₄ Abstraction Reaction Dynamics: Product Energy Partitioning

H + CD₄ Abstraction Reaction Dynamics: Product Energy Partitioning