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Intramolecular dynamics by photoelectron spectroscopy. III.Predissociation of the B 2B2 state of H2O+ and D2O+ by a semiclassical approach Dehareng, Dominique in Chemical Physics (1986), 110 The initial wave packets and H2O+ and D2O+ in their B 2B2 /2A' states are expanded in the frozen gaussian basis set proposed by Heller. The gaussian functions are propagated on the adiabatic and diabatic ... [more ▼] The initial wave packets and H2O+ and D2O+ in their B 2B2 /2A' states are expanded in the frozen gaussian basis set proposed by Heller. The gaussian functions are propagated on the adiabatic and diabatic potential energy surfaces resulting from the conical intersection with the A 2A1/2A' states. Autocorrelation functions are calculated separately for the adiabatic and the diabatic motions of the nuclei. These autocorrelation functions are compared with their experimental counterparts. The agreement is qualitatively good and the isotope effects are well accounted for. [less ▲] Detailed reference viewed: 22 (2 ULg)Nonadiabatic Unimolecular Reactions of Polyatomic Molecules Desouter-Lecomte, Michèle ; Dehareng, Dominique ; et al in Journal of Physical Chemistry (1985), 89 The nonadiabatic couplings which arise when two potential energy surfaces of a polyatomic molecule get close in energy can be classified as follows: (A) avoided crossings, (B) genuine intersections (Jahn ... [more ▼] The nonadiabatic couplings which arise when two potential energy surfaces of a polyatomic molecule get close in energy can be classified as follows: (A) avoided crossings, (B) genuine intersections (Jahn-Teller and conical), (C) glancing intersections (Renner-Teller interactions). The characteristics of the potential energy surfaces in the adiabatic and diabatic representations are discussed for each case. The three coupling cases differ in the structure of the Hamiltonian matrix. When the latter is written in the diabatic representation, it is meaningful to retain the leading term only in its power series expansion. This gives rise to a so-called minimum-order model which is found to be surprisingly accurate (at least in a restricted zone of nuclear coordinates) when compared to the results of ab initio calculations. The characteristic features of each coupling case can only be understood in a two-dimensional configuration space, Le., when two nuclear degrees of freedom, often with different symmetry properties, are explicitly considered. A simple expression of the nonadiabatic transition probability between two electronic states can be worked out in the framework of the minimum-order models. Two-dimensional extensions of the Landau-Zener formula are obtained, which can be used to study the consequences of the anisotropic properties of the coupling. In the case of avoided crossings, only nuclear trajectories having a well-defined direction are able to bring about surface hopping, wheras there exists two active degrees of freedom for conical intersections. Hence, nonadiabatic processes which are controlled by genuine intersections are expected to take place faster than those controlled by avoided crossings. [less ▲] Detailed reference viewed: 45 (3 ULg)The isomerization and fragmentation of the CHO2+ ions: an example of spin-controlled chemistry? ; Dehareng, Dominique ; et al in Advances in Mass Spectrometry (1985), X(B), 1129-1130 The article presents a study of the isomerization and fragmentation of the CHO2+ ions Detailed reference viewed: 23 (3 ULg)Calculation of autocorrelation functions for electronic spectra Dehareng, Dominique in Chemical Physics (1984), 84 The autocorrelation function C(t) associated with the vibrational motion in the A 2Pi u state of N2+ is calculated by three different methods. The classical method is based on classical trajectory ... [more ▼] The autocorrelation function C(t) associated with the vibrational motion in the A 2Pi u state of N2+ is calculated by three different methods. The classical method is based on classical trajectory calculations and provides good results except for secondary maxima appearing in the experimental autocorrelation function and resulting from interference effects. In the semiclassical method, the wavefunction is expanded in a basis of frozen gaussian functions. The secondary maxima are reproduced and the result is quite satisfactory. The superposition procedure consists in an expansion of the wavefunction in the eigenfunctions of the A state of N2+ and leads to a very simple formula for the autocorrelation function C(t). The secondary maxima are accounted for and the calculated function agrees very well with experimental results. [less ▲] Detailed reference viewed: 47 (5 ULg)Adiabatic-to-diabatic electronic state transformation and curvilinear nuclear coordinates for molecular systems ; ; Dehareng, Dominique in Chemical Physics Letters (1983), 95(2), 139-143 Following an original idea of Baer, since then several times applied to various small molecular collisional systems, it is shown that — whatever the choice of curvilinear generalized coordinates to ... [more ▼] Following an original idea of Baer, since then several times applied to various small molecular collisional systems, it is shown that — whatever the choice of curvilinear generalized coordinates to describe the molecular gometry and overall rotation — the algebraic framework proposed by Baer remains valid provided only that the exact tensorial expression of the kinetic energy operator is used. [less ▲] Detailed reference viewed: 80 (3 ULg)Dynamical study of non adiabatic unimolecular reactions: The conical intersection between the B 2B2 and Ã 2A1 states of H2O+. Dehareng, Dominique ; ; Lorquet, Jean-Claude et al in Journal of Chemical Physics (1983), 78(3), 1246-1264 The conical intersection conecting the B 2A' and A 2A' states of the H2O+ ion is studied. The two potential energy surfaces are calculated ab initio by the SCF/CI method within the Cs point group. The ... [more ▼] The conical intersection conecting the B 2A' and A 2A' states of the H2O+ ion is studied. The two potential energy surfaces are calculated ab initio by the SCF/CI method within the Cs point group. The nonadiabatic elements <A|d/dq|B> are computed for several cross sections throughout the potential energy surfaces. A transformation to the diabatic representation is performed. The linear model is found to be a good approximation in the region close to the apex of the cone. The global functions t(s) and T(S) governing the nonadiabatic transition probability are calculated; their shapes are those predicted by the Landau-Zener model (in the Nikitin bidimensional version). A dynamical study is undertaken by means of classical trajectory calculations on the upper adiabatic potential energy surface. An average transition probability Ptr is derived. Excitation of rotation or of the bending mode of H2O before photon impact has no influence on Ptr. Excitation of the symmetrical or antisymmetrical valence mode of H2O lowers Ptr. The shape of ln(1-Ptr) as a function of time indicates the existence of two distinct regimes at short and intermediate time ranges, characterized by two different rate constants k1 and k2 respectively. The rate constants are of the order of 10exp(14) s-1. k1 exhibits a maximum as a function of the absorbed energy Eabs whereas k2 decreases as a function of Eabs. [less ▲] Detailed reference viewed: 31 (4 ULg)Intramolecular Dynamics of Molecular Ions. Lorquet, Jean-Claude ; Lorquet, Andrée ; Dehareng, Dominique et al in Bulletin de la Société Chimique Belge (1983), 92(6/7), 609-611 The Fourier transform of an electronic spectrum gives a direct dynamic information on the nuclear motion of a wavepacket on the potential energy surface of the final state reached in the electronic ... [more ▼] The Fourier transform of an electronic spectrum gives a direct dynamic information on the nuclear motion of a wavepacket on the potential energy surface of the final state reached in the electronic transition, at least during the first few molecular vibrations. The method is valid for both adiabatic and non-adiabatic situations. It has proved its usefulness in the study of molecular processes such as Duchinsky effect, fast predissociations and internal conversions. [less ▲] Detailed reference viewed: 55 (16 ULg)Intramolecular dynamics by photoelectron spectroscopy. II. Nonadiabatic processes. Dehareng, Dominique ; Leyh, Bernard ; Desouter-Lecomte, Michèle et al in Journal of Chemical Physics (1983), 79(8), 3719-3724 The Fourier transform of an electronic spectrum leads to an autocorrelation function which provides information on the propagation of the wave packet on the potential energy surface of the electronic ... [more ▼] The Fourier transform of an electronic spectrum leads to an autocorrelation function which provides information on the propagation of the wave packet on the potential energy surface of the electronic state reached in the transition. The formula is valid even when nonadiabatic interaction is present, i.e., when the wave packet splits at a particular surface crossing with one part branching off to another potential energy surface. An explicit expression of the correlation function is given for a model of several discrete states interacting with a continuum. Closed-form solutions are given in the case of one and two resonances. A very simple formula valid in the strong coupling limit is also derived. The method is applied to the photoelectron spectrum of state A 2Sigma+ of HBr+, which is shown to correspond to the strong couplig case. [less ▲] Detailed reference viewed: 23 (5 ULg)Quelques aspects théoriques du problème des demi-collisions ; Dehareng, Dominique in Nouveau Journal de Chimie (1981), 5 Detailed reference viewed: 7 (0 ULg)Potential energy surfaces and dissociation mechanisms of molecular ions Lorquet, Jean-Claude ; Dehareng, Dominique ; et al in Journal de Chimie Physique (1980), 77 Detailed reference viewed: 8 (1 ULg) |
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