Photofragmentation of H2S in the first continuum

Veen, G. N. A. van; Mohamed, K.A.; Baller, T.; Vries, A.E. De

doi:10.1016/0301-0104(83)80029-9

Cited by 119 publications

(43 citation statements)

References 41 publications

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“…However this effect is not sufficiently large at the fast fragment velocities observed to explain the discrepancy. A second, and probably more important, source arises from the much higher laser flux used by van Veen et al We estimate from their quoted experimental conditions [42] that, due to a more powerful laser and tighter focusing, this was probably a factor of 10-20 times higher than that used by Barry and Gorry [1]. It is known that at high fluxes the observed anisotropy decreases due to saturation effects [43,44].…”

Section: State Symmetriesmentioning

confidence: 83%

Photofragmentation dynamics of n-C₃H₇I and i-C₃H₇I at 248 nm

1987

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Translational photofragment spectroscopy has been used to study the photodissociation dynamics of n-C3HTI and i-C3HTI at 248 nm. The measured anisotropies of the photofragments show that the initial absorption is the (parallel polarized) 3Qo*--N transition with a dissociation lifetimes of 3.7 + 2 x 10 13s and 2.5 + 2 x 10-13s respectively. The time of flight measurements yield the energy disposal for channels leading to I(2P3/2) and I*(2P1/2) for both molecules, although with greater uncertainty for i-C3H7I. The average energy disposed into translation is 43 per cent (I) and 52 per cent (I*) for n-C3H7I , and 39 per cent (I) and 57 per cent (I*) for i-C3H7I.The energy disposal for a variety of alkyl iodides are found to be well described by an impulsive model of the dissociation dynamics with the niodoalkanes showing a near constant width for the translational energy distribution regardless of its absolute value. A simple Landau-Zener curve crossing description is used to highlight the substantial change in curve crossing probability caused by substitution at the fl carbon or change to a secondary structure for the radical. Finally a model which combines the soft-radical impulse model for energy disposal with the Landau-Zener curve crossing probability is found to provide an excellent description of the I* quantum yields for the n-iodoalkanes.

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Section: State Symmetriesmentioning

confidence: 83%

Photofragmentation dynamics of n-C₃H₇I and i-C₃H₇I at 248 nm

1987

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“…Absorption cross sections for HI at 248 and 266 nm were taken from ref, 62. In the case where the 248 and 266 nm HI photolysis was used to generate H atoms, the absorption cross sections given in ref. 62 were multiplied with the I (~P~~~)~I (~P~~~) branching ratios given in ref. 62.…”

Section: A H + D20mentioning

confidence: 99%

“…62 were multiplied with the I (~P~~~)~I (~P~~~) branching ratios given in ref. 62. This was necessary to account for the fact that at both photodissociation wavelengths only the "fast" H atoms from the H + dissociation channel have enough energy to overcome the reaction barrier.…”

Section: A H + D20mentioning

confidence: 99%

Reaction dynamics studies of a simple tetraatomic system: AA + BA ↔ A + ABA

Koppe¹,

Thomas²,

Naik³

et al. 1994

Can. J. Chem.

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. 72, 615 (1994).We have studied the reaction of translationally excited hydroxyl radicals with molecular hydrogen at different center-of-mass energies. H/D atoms produced in the reaction have been detected under single collision conditions by means of vacuum ultraviolet laser-induced fluorescence at the Lyman-a transition. By calibrating the H/D signals from the reaction against H atom signals from the H2S and HC1 photolysis, respectively, the following absolute reactive cross sections were determined: OH + H2 + H + H20: uR(O. At different center-of-mass collision energies nascent population distributions of the OD product fine-structure components were determined. It has been found that at all collision energies OD radicals are produced exclusively in their vibrational ground state, with only a small amount of the total available energy appearing in the rotational degree of freedom. A comparison of the dependence of the reaction cross section on the translational energy shows that relative reagent translation is more effective to promote reactivity in the reaction OH + H2 and OH + D2 than in the reaction H + D20. This, together with a preferential population of the symmetric 2 n (~' ) A-doublet state (with the unpaired .ir orbital lying in the plane of rotation) at high OD rotational quantum numbers, suggests that the reaction H + D 2 0 + OD + HD proceeds through a planar transition state via a direct mechanism, where the OD moiety acts as a spectator, and where the reaction barrier is located at a "later" position of the reaction coordinate. cas, pour dCtecter les radicaux OD produits dans des conditions de collision unique, avec une rksolution de I'ktat quantique, on a fait appel i la fluorescence induite au laser. En calibrant les signaux OD de la rCaction I'aide de signaux OH obtenus par photolyse de H202, on a mesurk les sections droites absolues de la rCaction H + D 2 0 + OD + HD : uR(l ,5 eV) = (0,07 t 0,04) A2, uR(1,8 eV) = (0,10 t 0,03) A2 et uR(2,2 eV) = (0,11 2 0,03) A2. On a determink, 2 diverses Cnergies de collision du centre de masse, les distributions de population naissante de composantes de la structure fine du produit OD. On a trouvk que, pour toutes les Cnergies de collision, les radicaux OD ne sont produits que dans leur ktat vibrationnel fondamental; seule une faible partie de l'knergie totale disponible appardt dans le degrC de libert6 rotationnel. Une comparaison de la dkpendance de la section droite de la rkaction sur l'knergie de translation montre que la translation relative du rkactif est plus efficace pour promouvoir la rdactivitk dans les rkactions OH + H2 et OH + D2 que dans la reaction H + D20. Ce rksultat, pris avec le fait que la population de I'ktat doublet symktrique-A, 2 n (~' ) (comportant une orbitale TI non appariCe se trouvant dans le plan de rotation), est prCfCrke pour les nombres quantiques klevks de OD, suggkre que la r6action H + D 2 0 + OH + HD se produit par un mkcanisme direct impliquant un ktat de transition plan alors que la portion OD agit comme spectateur et...

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“…This principle is commonly applied in gas phase photofragment translational energy spectroscopy to extract bond dissociation energies for small molecules (by assuming that D 0 ) hν -E Tmax ). 31 The complication in surface photochemical reactions is that the reagents may have energies in excess of that required to surmount the activation barrier for reaction, and some of this excess energy may be channeled into product translation. However, in common with thermal reactions, the reagent energy distribution is expected to be exponentially damped with increasing energy (i.e.…”

Section: Reaction Dynamics At Catalytic Metal Surfaces Harrisonmentioning

confidence: 99%

Photochemical Exploration of Reaction Dynamics at Catalytic Metal Surfaces: From Ballistics to Statistics

Harrison

1998

Acc. Chem. Res.

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Photofragmentation of H2S in the first continuum

Cited by 119 publications

References 41 publications

Photofragmentation dynamics of n-C₃H₇I and i-C₃H₇I at 248 nm

Photofragmentation dynamics of n-C₃H₇I and i-C₃H₇I at 248 nm

Reaction dynamics studies of a simple tetraatomic system: AA + BA ↔ A + ABA

Photochemical Exploration of Reaction Dynamics at Catalytic Metal Surfaces: From Ballistics to Statistics

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Photofragmentation of H2S in the first continuum

Cited by 119 publications

References 41 publications

Photofragmentation dynamics of n-C3H7I and i-C3H7I at 248 nm

Photofragmentation dynamics of n-C3H7I and i-C3H7I at 248 nm

Reaction dynamics studies of a simple tetraatomic system: AA + BA ↔ A + ABA

Photochemical Exploration of Reaction Dynamics at Catalytic Metal Surfaces: From Ballistics to Statistics

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Photofragmentation dynamics of n-C₃H₇I and i-C₃H₇I at 248 nm

Photofragmentation dynamics of n-C₃H₇I and i-C₃H₇I at 248 nm