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Control of molecular dynamics with zero-area fields. application to molecular orientation and photodissociation ; ; et al in Physical Review A (2014), 90 The constraint of time-integrated zero area on the laser field is a fundamental requirement, both theoretically and experimentally, in the control of molecular dynamics. By using techniques of local and ... [more ▼] The constraint of time-integrated zero area on the laser field is a fundamental requirement, both theoretically and experimentally, in the control of molecular dynamics. By using techniques of local and optimal control theory, we show how to enforce this constraint in two benchmark control problems, namely, molecular orientation and photofragmentation. The origin and the physical implications for the dynamics of this zero-area control field are discussed. [less ▲] Detailed reference viewed: 22 (3 ULg)Photodissociation and radiative association ofHeH+ in the metastable triplet state ; ; Desouter-Lecomte, Michèle et al in Journal of Physical Chemistry A (2013), 117 Detailed reference viewed: 13 (1 ULg)Proposal for laser purification in molecular vibrational cooling using zero-width resonances ; ; et al in Physical Review. A (2013), 87(3), 031403 Detailed reference viewed: 14 (0 ULg)Characterization of the MgO2+ dication in the gas phase: electronic states, spectroscopy and atmospheric implications ; ; et al in Physical Chemistry Chemical Physics [=PCCP] (2013), 15(3), 824-831 Detailed reference viewed: 16 (0 ULg)Implementing quantum algorithms in hyperfine levels of ultracold polar molecules ; ; Desouter-Lecomte, Michèle in Journal of Physics: Conference Series (2012), 388(11), 112010 Detailed reference viewed: 16 (0 ULg)Local control of nonadiabatic photodissociation dynamics using Møller operators ; ; et al in Journal of Physics: Conference Series (2012), 388(11), 112009 Detailed reference viewed: 14 (0 ULg)Controlled full adder or subtractor by vibrational quantum computing ; ; Remacle, Françoise et al in Physical Review. A (2009), 80(2), A controlled full addition or subtraction can be realized by a unitary transformation on a register of four qubits. The fourth qubit is then used as a control qubit to enforce the addition or the ... [more ▼] A controlled full addition or subtraction can be realized by a unitary transformation on a register of four qubits. The fourth qubit is then used as a control qubit to enforce the addition or the subtraction of two binary digits and a carry or a borrow. The transformation can be decomposed into six elementary gates. The network differs from the adder network of four elementary gates by including two new controlled-NOT gates. The scheme is general and its implementation using vibrational computing has the advantage that the single global transformation that connects the inputs to the outputs can be driven in one step by a single laser shot. This decreases the time of operation and allows for a better use of the optical resources and for an improvement of the fidelity. The laser pulses are optimized by optimal control theory. [less ▲] Detailed reference viewed: 62 (6 ULg)Computational investigation and experimental considerations for the classical implementation of a full adder on SO2 by optical pump-probe schemes ; ; Remacle, Françoise et al in Journal of Chemical Physics (2008), 128(19), Following the scheme recently proposed by Remacle and Levine [Phys. Rev. A 73, 033820 (2006)], we investigate the concrete implementation of a classical full adder on two electronic states ((X) over tilde ... [more ▼] Following the scheme recently proposed by Remacle and Levine [Phys. Rev. A 73, 033820 (2006)], we investigate the concrete implementation of a classical full adder on two electronic states ((X) over tilde (1)A(1) and (C) over tilde B-1(2)) of the SO2 molecule by optical pump-probe laser pulses using intuitive and counterintuitive (stimulated Raman adiabatic passage) excitation schemes. The resources needed for providing the inputs and reading out are discussed, as well as the conditions for achieving robustness in both the intuitive and counterintuitive pump-dump sequences. The fidelity of the scheme is analyzed with respect to experimental noise and two kinds of perturbations: The coupling to the neighboring rovibrational states and a finite rotational temperature that leads to a mixture for the initial state. It is shown that the logic processing of a full addition cycle can be realistically experimentally implemented on a picosecond time scale while the readout takes a few nanoseconds. (c) 2008 American Institute of Physics. [less ▲] Detailed reference viewed: 9 (1 ULg)Vibrational computing: Simulation of a full adder by optimal control ; ; Remacle, Françoise et al in Journal of Chemical Physics (2008), 128(6), Within the context of vibrational molecular quantum computing, we investigate the implementation of a full addition of two binary digits and a carry that provides the sum and the carry out. Four qubits ... [more ▼] Within the context of vibrational molecular quantum computing, we investigate the implementation of a full addition of two binary digits and a carry that provides the sum and the carry out. Four qubits are necessary and they are encoded into four different normal vibrational modes of a molecule. We choose the bromoacetyl chloride molecule because it possesses four bright infrared active modes. The ground and first excited states of each mode form the one-qubit computational basis set. Two approaches are proposed for the realization of the full addition. In the first one, we optimize a pulse that implements directly the entire addition by a single unitary transformation. In the second one, we decompose the full addition in elementary quantum gates, following a scheme proposed by Vedral [Phys. Rev. A 54, 147 (1996)]. Four elementary quantum gates are necessary, two two-qubit CNOT gates (controlled NOT) and two three-qubit TOFFOLI gates (controlled-controlled NOT). All the logic operations consist in one-qubit flip. The logic implementation is therefore quasiclassical and the readout is based on a population analysis of the vibrational modes that does not take the phases into account. The fields are optimized by the multitarget extension of the optimal control theory involving all the transformations among the 2(4) qubit states. A single cycle of addition without considering the preparation or the measure or copy of the result can be carried out in a very competitive time, on a picosecond time scale. (C) 2008 American Institute of Physics. [less ▲] Detailed reference viewed: 28 (3 ULg)Dynamics of complex molecular systems with numerical kinetic energy operators in generalized coordinates ; ; Dive, Georges et al in Chemical Physics (2006), 326(2-3), 500-508 Dynamics of complex molecular systems in generalized coordinates (q,p) using numerical kinetic energy operators is investigated. The kinematical tools necessary for quantum, classical or semiclassical ... [more ▼] Dynamics of complex molecular systems in generalized coordinates (q,p) using numerical kinetic energy operators is investigated. The kinematical tools necessary for quantum, classical or semiclassical dynamics with or without constraints mainly come from the covariant and contravariant components of the metric tensor and their derivatives up to the second ones. These quantities are computed numerically but without any other approximation than the numerical precision by the code TNUM. This code generates kinetic energy operators in the internal coordinates of the Z-matrix describing the molecular frame geometry in the ab initio quantum chemistry step or in symmetry adapted coordinates [D. Lauvergnat, A. Nauts, J. Chem. Phys. 116 (2002) 8560]. Various reduced dimensionality models can be used in the upgraded code. The interface with an ab initio code is calibrated on a 22-atom system for which a two-dimensional quantum treatment with a constrained Hamiltonian has been carried out previously. The test application concerns the spreading properties of a wave packet in an unstable flat region around a valley ridge inflexion point between two transition states in the Endo-dimerization of cyclopentadiene. We perform here on-the-fly classical or semiclassical dynamics in full or reduced dimensionality. (c) 2006 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 27 (1 ULg)Quantum effects in competitive unimolecular reactions Remacle, Françoise ; Desouter-Lecomte, Michèle ; Lorquet, Jean-Claude in Chemical Physics (1991), 153(1-2), 201-217 The decay law P(t) of a microcanonical ensemble of metastable states prepared in an energy interval δE is usually nonexponential because the widths Γ of each individual resonance fluctuate around an ... [more ▼] The decay law P(t) of a microcanonical ensemble of metastable states prepared in an energy interval δE is usually nonexponential because the widths Γ of each individual resonance fluctuate around an energy-dependent average K(E) which is satisfactorily approximated by RRKM theory. The kinetic equations used at the macroscopic level are therefore not necessarily transferable to elementary processes when the interval δE contains more than a single resonance. For example, two competitive unimolecular reactions need not be characterized by the same effective evolution in time. Particular attention is focused on the quantum expressions of the yields of fragmentation Yk(E, t) when they differ from those Fk(E, t) derived from the macroscopic kinetic scheme. The discussion is based on the value of the parameter νeff = 2K(E)2/σ2 which is a measure of the dispersion of the individual rate constants. Two applications are presented. First, we consider a competition between an electronic and a vibrational predissociation in a triatomic van der Waals-like model with a sparse density of states and a maximum number of selection rules. The shorter the lifetime, the larger the dispersion of the widths of the resonances lying within δE, and the more severe the discrepancy between Yk(E, t) and Fk(E, t). In the quantum treatment, fragmentation proceeds with unequal effective rate constants in the two decay channels. The second application deals with the other extreme where the density of states is so large that statistical methods are useful. Explicit quantum mechanical expressions of the yields in a competitive fragmentation process are given for some distributions of the widths, χν 2 and convolutions of χν 2. Here again, a discrepancy can be observed between Yk(E, t) and Fk(E, t): competitive unimolecular reactions need not be characterized by the same rate. It is demonstrated that, when the density of states is so large that the resonances are quasi-degenerate, the mean and the variance of the widths can be obtained from the invariant Ω matrix. When the resonances overlap, the variance of the widths is always greater than the variance of any kind of zero-orders widths. Except in unrealistic cases (either because a single resonance is excited or because all the widths are the same) it is dubious to disprove a mechanism on the basis of arguments borrowed from conventional macroscopic kinetics in an energy-resolved experiment as has been done many times in the past. © 1991. [less ▲] Detailed reference viewed: 6 (0 ULg)Constructing approximatively diabatic states from LCAO-SCF-CI calculations Desouter-Lecomte, Michèle ; Dehareng, Dominique ; Lorquet, Jean-Claude in Journal of Chemical Physics (1987), 86(3), 1429-1436 We consider here two approaches which have been proposed in the literature to obtain diabatic states from ab initio calculations. First by calculating explicitely the coupling vector g which describes the ... [more ▼] We consider here two approaches which have been proposed in the literature to obtain diabatic states from ab initio calculations. First by calculating explicitely the coupling vector g which describes the nonadiabatic interaction between the adiabatic states. Second, by some extrapolation process of the wavefunctions obtained at a particular reference point. The coupling vector is a sum of three contributions. The first two represent the the change in character of the adiabatic states in the region of nonadiabatic coupling due the variation of the CI and LCAO coefficients, whereas the third results from the translation of the atomic orbitals with the moving nuclear centers. Criteria have been given to recognize when it is possible to transform a set of CI wave functions into a pair of useful diabatic states. A particularly favorable situation is obtained when the interacting electronic states are doubly excited with respect to each other. Within the two-states approximation, the first term, depending on the CI coefficients, is strictly irrotational and never gives rise to problems. One can expect situations where it is also true for the second term depending on the LCAO coefficients. However, the third term of the coupling can never be described as a rotation of two diabatic functions. Nevertheless, the latter contribution can frequently be neglected, at least when the coupling is strong. The theory of the electron transfer factors (ETF's) provides further insight into the problem and confirm our conclusions. [less ▲] Detailed reference viewed: 54 (4 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: 43 (3 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) |
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