Crossed beams and theoretical studies of the O(3P)+CH4→H+OCH3 reaction excitation function

Troya, Diego; Schatz, George C.; Garton, Donna J.; Brunsvold, Amy L.; Minton, Timothy K.

doi:10.1063/1.1631254

Cited by 79 publications

(122 citation statements)

References 22 publications

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“…The good agreement between the experimental results and the predictions of the QCT calculations, which used only the three low-lying triplet potential energy surfaces, suggests that ISC does not play an important role in the dynamics of O( 3 P) + CO collisions. The absence of ISC was also a conclusion in the measurements of the excitation functions for O( 3 P) + H 2 f OH + H, 25 and O( 3 P) + CH 4 f OCH 3 + H, 9 and in the dynamics of the reaction O( 3 P) + D 2 f OD +D. 8 The c.m.…”

Section: Discussionmentioning

confidence: 92%

Dynamics of Hyperthermal Collisions of O(³P) with CO

Brunsvold¹,

Upadhyaya²,

Zhang³

et al. 2008

J. Phys. Chem. A

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The dynamics of O(3P) + CO collisions at a hyperthermal collision energy near 80 kcal mol-1 have been studied with a crossed molecular beams experiment and with quasi-classical trajectory calculations on computed potential energy surfaces. In the experiment, a rotatable mass spectrometer detector was used to monitor inelastically and reactively scattered products as a function of velocity and scattering angle. From these data, center-of-mass (c.m.) translational energy and angular distributions were derived for the inelastic and reactive channels. Isotopically labeled C18O was used to distinguish the reactive channel (16O + C18O 16OC + 18O) from the inelastic channel (16O + C18O 16O + C18O). The reactive 16OC molecules scattered predominantly in the forward direction, i.e., in the same direction as the velocity vector of the reagent O atoms in the c.m. frame. The c.m. translational energy distribution of the reactively scattered 16OC and 18O was very broad, indicating that 16OC is formed with a wide range of internal energies, with an average internal excitation of approximately 40% of the available energy. The c.m. translational energy distribution of the inelastically scattered C18O and 16O products indicated that an average of 15% of the collision energy went into internal excitation of C18O, although a small fraction of the collisions transferred nearly all the collision energy into internal excitation of C18O. The theoretical calculations, which extend previously published results on this system, predict c.m. translational energy and angular distributions that are in near quantitative agreement with the experimentally derived distributions. The theoretical calculations, thus validated by the experimental results, have been used to derive internal state distributions of scattered CO products and to probe in detail the interactions that lead to the observed dynamical behavior.

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Section: Discussionmentioning

confidence: 92%

Dynamics of Hyperthermal Collisions of O(³P) with CO

Brunsvold¹,

Upadhyaya²,

Zhang³

et al. 2008

J. Phys. Chem. A

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“…In earlier studies from our laboratories on the H-atom elimination reactions, O + H 2 f OH + H 47 and O + CH 4 f OCH 3 + H, 48 an excited 3 A′ contribution was required to explain the observed excitation function. Although the cone of acceptance for the higher energy surface is smaller, 29 the necessity of the inclusion of both surfaces for some H-atom elimination reactions while only the lower energy surface was sufficient to explain the observed data for the O + HCl f ClO + H reaction may lead one to speculate that the present result is the fortuitous outcome of the inaccuracies in the B3LYP calculations.…”

Section: Discussionmentioning

confidence: 99%

“…angle in the laboratory frame provides a good approximation of the relative product flux for the whole Newton sphere. We have used such measurements to determine relative excitation functions for the reactions, O + H 2 f OH + H, 47 O + CH 4 f OCH 3 + H, 48 and O + H 2 O f HO 2 + H. 32 However, for the reaction, O + HCl f ClO + H, the c.m. recoil velocities of ClO are relatively large compared to the velocity of the c.m.…”

Section: Experimental Methodsmentioning

confidence: 99%

Crossed-Beams and Theoretical Studies of Hyperthermal Reactions of O(³P) with HCl

et al. 2010

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The reaction of O( 3 P) with HCl at hyperthermal collision energies (45-116 kcal mol -1 ) has been investigated with crossed-molecular beams experiments and direct dynamics quasi-classical trajectory calculations. The reaction may proceed by two primary pathways, (1) H-atom abstraction to produce OH and Cl and (2) H-atom elimination to produce H and ClO. The H-atom abstraction reaction follows a stripping mechanism, in which the reagent O atom approaches the HCl molecule at large impact parameters and the OH product is scattered in the forward direction, defined as the initial direction of the reagent O atoms. The H-atom elimination reaction is highly endoergic and requires low-impact-parameter collisions. The excitation function for ClO increases from a threshold near 45 kcal mol -1 to a maximum around 115 kcal mol -1 and then begins to decrease when the ClO product can be formed with sufficient internal energy to undergo secondary dissociation. At collision energies slightly above threshold for H-atom elimination, the ClO product scatters primarily in the backward direction, but as the collision energy increases, the fraction of these products that scatter in the forward and sideways directions increases. The dependence of the angular distribution of ClO on collision energy is a result of the differences in collision geometry. Collisions where the H atom on HCl is oriented away from the incoming reagent O atom lead to backward-scattered ClO and those where the H atom is oriented toward the incoming O atom lead to forward-scattered ClO. The latter trajectories do not follow the minimum energy path and involve larger translational energy release. Therefore, they become dominant at higher collision energies because they lead to lower internal energies and more stable ClO products. The H-atom abstraction and elimination reactions have comparable cross sections for hyperthermal O( 3 P) + HCl collisions.

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“…Its thermal kinetics has been extensively studied both experimentally 2 and theoretically. [3][4][5][6][7][8][9][10][11][12] There are also a few experimental studies of the ground-state reaction dynamics, [13][14][15][16][17] from which the key observations can be summarized as follows. (1) The OH rotational distribution is relatively cold.…”

mentioning

confidence: 99%

Communication: Imaging the effects of the antisymmetric-stretching excitation in the O(3P) + CH4(v3 = 1) reaction

Pan

Liu

2014

The Journal of Chemical Physics

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Effects of one-quantum excitation of the antisymmetric-stretching mode of CH4(v3 = 1) on the O(3P) + CH4 reaction were studied in a crossed-beam, ion-imaging experiment. In the post-threshold region, we found that (1) the product state distributions are dominated by the CH3(00) + OH(v′ = 1) pair, (2) the product angular distributions extend toward sideways from the backward dominance of the ground-state reaction, and (3) vibrational excitation exerts a positive effect on reactivity, but translational energy is more efficient in promoting the rate of this central-barrier reaction. All major findings agree reasonably well with recent theoretical results. Some remaining questions are pointed out.

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Crossed beams and theoretical studies of the O(3P)+CH4→H+OCH3 reaction excitation function

Cited by 79 publications

References 22 publications

Dynamics of Hyperthermal Collisions of O(³P) with CO

Dynamics of Hyperthermal Collisions of O(³P) with CO

Crossed-Beams and Theoretical Studies of Hyperthermal Reactions of O(³P) with HCl

Communication: Imaging the effects of the antisymmetric-stretching excitation in the O(3P) + CH4(v3 = 1) reaction

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Crossed beams and theoretical studies of the O(3P)+CH4→H+OCH3 reaction excitation function

Cited by 79 publications

References 22 publications

Dynamics of Hyperthermal Collisions of O(3P) with CO

Dynamics of Hyperthermal Collisions of O(3P) with CO

Crossed-Beams and Theoretical Studies of Hyperthermal Reactions of O(3P) with HCl

Communication: Imaging the effects of the antisymmetric-stretching excitation in the O(3P) + CH4(v3 = 1) reaction

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Dynamics of Hyperthermal Collisions of O(³P) with CO

Dynamics of Hyperthermal Collisions of O(³P) with CO

Crossed-Beams and Theoretical Studies of Hyperthermal Reactions of O(³P) with HCl