CEPA calculations of potential energy surfaces for open-shell systems.

Staemmler, Volker; Palma, Amedeo

doi:10.1016/0301-0104(85)85049-7

Cited by 147 publications

(48 citation statements)

References 23 publications

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“…The photodissociation of water in the ®rst absorption band was considered as a fast and direct bond breaking process on a single PES. The quantum mechanical timeindependent [51] and time-dependent dynamics calculations [52] mostly used a semiempirical ground state PES [53] and an ab initioÃ A state surface [54]. These studies predicted isotopic branching ratios for the photodissociation , via two distinguishable channels leading to HOD !…”

Section: Water Isotopomersmentioning

confidence: 99%

Controlling bond cleavage and probing intramolecular dynamics via photodissociation of rovibrationally excited molecules

Bar¹,

Rosenwaks²

2001

International Reviews in Physical Chemistry

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Photodissociation studies of vibrationless ground state molecules pervade diverse areas of chemical physics, while those of rovibrationally excited molecules are expected to have even more impact due to the additional fascinating possibilities they o er and the new horizons they open. Photodissociation of rovibrationally excited species involves a double-resonance scheme in which a photodissociative transition is initiated from an excited rovibrational state that might substantially a ect the intensity and wavelength dependence of the photoabsorption spectrum. In favourable cases, when the energy is disposed in vibrations that are strongly coupled to the reaction coordinate, this pre-excitation might in¯uence photodissociation pathways and lead to selective bond cleavage. In other cases it might in¯uence the branching ratio between di erent fragments by altering the photodissociation dynamics. Moreover, the photodissociation of rovibrationally excited species can serve as a sensitive means for detection of weak vibrational overtone transitions of jet-cooled molecules, and therefore a promising way for revealing speci®c couplings and time evolution of the prepared vibrational states. Experimental studies on di erent polyatomics are used to demonstrate the above aspects and to show how the mechanism of chemical transformations and the nature of rovibrationally excited states are highlighted by photolysis of these pre-excited molecules.

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Section: Water Isotopomersmentioning

confidence: 99%

Controlling bond cleavage and probing intramolecular dynamics via photodissociation of rovibrationally excited molecules

Bar¹,

Rosenwaks²

2001

International Reviews in Physical Chemistry

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“…First, an accurate three-dimensional ͑3D͒ potential had been calculated. 2 Second, the transition state on the 1 1 AЉ state surface is located at the HOH bond angle ␤ϭ104.5°and OH bond lengths r OH1 ϭr OH2 ϭ2.1 bohr, which is not far from the minimum on the ground-state surface (ϭ104.5°, r OH1 ϭr OH2 ϭ1.8 bohr). As a consequence, the dissociation is very direct and the nuclear wave function is located on a limited region of the potential energy surface.…”

Section: Introductionmentioning

confidence: 99%

Photodissociation of water. II. Wave packet calculations for the photofragmentation of H2O and D2O in the B̃ band

Harrevelt¹,

Hemert²

2000

The Journal of Chemical Physics

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A complete three-dimensional quantum mechanical description of the photodissociation of water in the B̃ band, starting from its rotational ground state, is presented. In order to include B̃-X̃ vibronic coupling and the B̃-Ã Renner–Teller coupling, diabatic electronic states have been constructed from adiabatic electronic states and matrix elements of the electronic angular momentum operators, following the procedure developed by A. J. Dobbyn and P. J. Knowles [Mol. Phys. 91, 1107 (1997)], using the ab initio results discussed in the preceding paper. The dynamics is studied using wave packet methods, and the evolution of the time-dependent wave function is discussed in detail. Results for the H2O and D2O absorption spectra, OH(A)/OH(X) and OD(A)/OD(X) branching ratios, and rovibrational distributions of the OH and OD fragments are presented and compared with available experimental data. The present theoretical results agree at least qualitatively with the experiments. The calculations show that the absorption spectrum and the product state distributions are strongly influenced by long-lived resonances on the adiabatic B̃ state. It is also shown that molecular rotation plays an important role in the photofragmentation process, due to both the Renner–Teller B̃-X̃ mixing, and the strong effect of out-of-plane molecular rotations (K>0) on the dynamics at near linear HOH and HHO geometries.

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“…3 This permits a rigorous dynamical analysis of the final-state interaction to be undertaken. 6 In a recent investigation 7 we have shown that rotationally inelastic effects are negligibly weak for this system because the ground-and excited-state potential-energy surfaces have roughly the same equilibrium angle and the angular and radial motions on these surfaces are almost completely decoupled.…”

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confidence: 99%

Photodissociation of SingleH2O Quantum States in the First Absorption Band: Complete Characterization of OH Rotational andΛ-Doublet State Distributions

Schinke¹,

Engle²,

Andresen³

et al. 1985

Phys. Rev. Lett.

112

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A complete characterization of rotational and electronic fine-structure-state distributions of the product OH from photodissociation of H 2 0 in the first absorption band is presented. Vibrationally excited water molecules are prepared in a well-defined rotational state by ir excitation, and photodissociation of this state is studied. The theory is based on numerically exact wave functions for ground-state water; the dissociative wave function is expanded in terms of OH( 2 n) wave functions (including electronic structure) and inelastic effects in the excited state are shown to be negligible. The comparison between theory and experiment is quantitative on the basis of six quantum numbers.PACS numbers: 34.50.Pi, 82.50.EtRecent years have witnessed growing interest in the understanding of photodissociation processes in small molecules. Modern laser methods allow true state-tostate experiments, which were not possible some years ago, 1 and detailed dynamical methods have been devised 2 to interpret such experiments. While considerable progress has been made in the understanding of the observations which result from modern photodissociation experiments, we believe that the comparison presented in this Letter represents the most detailed theoretical characterization yet achieved of an experimentally observed product-state distribution. The dynamical treatment used contains absolutely no adjustable parameters.A quantitative comparison of a state-to-state experiment with ab initio theory is reported for the photodissociation of H 2 0 in its first absorption band. This is one of the fortunate cases, where a particularly clear and simple situation is encountered and accurate quantum calculations are feasible. There is only one excited-state potential-energy surface involved, which has been determined by Staemmler and Palma. 3 Because of the repulsive nature of the surface no predissociation occurs. A series of experimental 4,5 as well as theoretical studies (neglecting the electronic structure of OH) 6,7 have already lead to promising agreement of experiment and theory.The completely state-to-state experiments reported here show unusual product quantum-state distributions. The experimental setup is described elsewhere. 5 By use of a tunable ir laser H 2 0 is vibrationally excited to a single rotational state. The photodissociation of this quantum state is studied at 193 nm and the nascent OH product-state distribution is analyzed by laser-induced fluorescence. The measured quantumstate distributions are obtained for the vi = v 2 = 0, v 3 = 1 state of H 2 0 with total angular momentum J, = 4 and different projection quantum numbers.We note the following observations: (1) The rotational-state distributions for a given A doublet are considerably structured (see Fig. 1).(2) The oscillations are in opposite sense for different A-doublet states (see Fig. 2). (3) For a given A doublet and rotational state the spin states are approximately populated according to their statistical weights. (4) The distributions depend sensitively ...

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CEPA calculations of potential energy surfaces for open-shell systems.

Cited by 147 publications

References 23 publications

Controlling bond cleavage and probing intramolecular dynamics via photodissociation of rovibrationally excited molecules

Controlling bond cleavage and probing intramolecular dynamics via photodissociation of rovibrationally excited molecules

Photodissociation of water. II. Wave packet calculations for the photofragmentation of H2O and D2O in the B̃ band

Photodissociation of SingleH2O Quantum States in the First Absorption Band: Complete Characterization of OH Rotational andΛ-Doublet State Distributions

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