Publications
151 results found
Vacher M, Steinberg L, Jenkins AJ, et al., 2015, Electron dynamics following photoionization: decoherence due to the nuclear-wave-packet width, Physical Review A, Vol: 92, Pages: 1-6, ISSN: 1094-1622
The advent of attosecond techniques opens up the possibility to observe experimentally electron dynamics following ionization of molecules. Theoretical studies of pure electron dynamics at single fixed nuclear geometries in molecules have demonstrated oscillatory charge migration at a well-defined frequency but often neglecting the natural width of the nuclear wave packet. The effect on electron dynamics of the spatial delocalization of the nuclei is an outstanding question. Here, we show how the inherent distribution of nuclear geometries leads to dephasing. Using a simple analytical model, we demonstrate that the conditions for a long-lived electronic coherence are a narrow nuclear wave packet and almost parallel potential-energy surfaces of the states involved. We demonstrate with numerical simulations the decoherence of electron dynamics for two real molecular systems (paraxylene and polycyclic norbornadiene), which exhibit different decoherence time scales. To represent the quantum distribution of geometries of the nuclear wave packet, the Wigner distribution function is used. The electron dynamics decoherence result has significant implications for the interpretation of attosecond spectroscopy experiments since one no longer expects long-lived oscillations.
Santolini V, Malhado JP, Robb MA, et al., 2015, Photochemical reaction paths of cis-dienes studied with RASSCF: the changing balance between ionic and covalent excited states, Molecular Physics, Vol: 113, Pages: 1978-1990, ISSN: 1362-3028
The balanced description of ionic and covalent molecular excited electronic states still presents a challenge for currentelectronic structure methods. In this contribution, we show how the restricted active space self-consistent field (RASSCF)method can be used to address this problem, applied to two dienes in the cis conformation. As with the closely relatedcomplete active space self-consistent field (CASSCF) method, the construction of the orbital active space in the RASSCFmethodology requires the a priori formulation of a physical or theoretical model of the system being studied. In this article,we discuss how the active space can be constructed in a guided and systematic way, using pairs of natural bond orbitalsas correlating partner orbitals (oscillator orbitals) and semi-internal correlation. The resulting balanced description of thecovalent and ionic valence excited states – with the ionic state correctly lower in energy at the Franck–Condon geometry –is suitable to study the photochemistry of these and other molecules.
Robb MA, Meisner J, Vacher M, et al., 2015, Geometric rotation of the nuclear gradient at a conical intersection: Extension to complex rotation of diabatic states, Journal of Chemical Theory and Computation, Vol: 11, Pages: 3115-3122, ISSN: 1549-9618
Nonadiabatic dynamics in the vicinity of conical intersections is of essential importance in photochemistry. It is well known that if the branching space is represented in polar coordinates, then for a geometry represented by angle θ, the corresponding adiabatic states are obtained from the diabatic states with the mixing angle θ/2. In an equivalent way, one can study the relation between the real rotation of diabatic states and the resulting nuclear gradient. In this work, we extend the concept to allow a complex rotation of diabatic states to form a nonstationary superposition of electronic states. Our main result is that this leads to an elliptical transformation of the effective potential energy surfaces; i.e., the magnitude of the initial nuclear gradient changes as well as its direction. We fully explore gradient changes that result from varying both θ and ϕ (the complex rotation angle) as a way of electronically controlling nuclear motion, through Ehrenfest dynamics simulations for benzene cation.
Vacher M, Meisner J, Mendive-Tapia D, et al., 2015, Electronic Control of Initial Nuclear Dynamics Adjacent to a Conical Intersection, JOURNAL OF PHYSICAL CHEMISTRY A, Vol: 119, Pages: 5165-5172, ISSN: 1089-5639
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- Citations: 26
Vigor WA, Spencer JS, Bearpark MJ, et al., 2015, Minimising biases in full configuration interaction quantum Monte Carlo, Journal of Chemical Physics, Vol: 142, ISSN: 1089-7690
Vacher M, Mendive-Tapia D, Bearpark MJ, et al., 2015, Electron dynamics upon ionization: Control of the timescale through chemical substitution and effect of nuclear motion, Journal of Chemical Physics, Vol: 142, ISSN: 1089-7690
Boggio-Pasqua M, Bearpark MJ, Rob MA, 2015, The Role of Extended Conical Intersection Seams in Photochromic Systems, International Conference of Computational Methods in Sciences and Engineering (ICCMSE), Publisher: AMER INST PHYSICS, Pages: 453-456, ISSN: 0094-243X
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- Citations: 2
Malhado JP, Bearpark MJ, Hynes JT, 2014, Non-adiabatic dynamics close to conical intersections and the surface hopping perspective., Frontiers in Chemistry, Vol: 2, ISSN: 2296-2646
Conical intersections play a major role in the current understanding of electronic de-excitation in polyatomic molecules, and thus in the description of photochemistry and photophysics of molecular systems. This article reviews aspects of the basic theory underlying the description of non-adiabatic transitions at conical intersections, with particular emphasis on the important case when the dynamics of the nuclei are treated classically. Within this classical nuclear motion framework, the main aspects of the surface hopping methodology in the conical intersection context are presented. The emerging picture from this treatment is that of electronic transitions around conical intersections dominated by the interplay of the nuclear velocity and the derivative non-adiabatic coupling vector field.
Mendive-Tapia D, Perrier A, Bearpark MJ, et al., 2014, New insights into the by-product fatigue mechanism of the photo-induced ring-opening in diarylethenes, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 16, Pages: 18463-18471, ISSN: 1463-9076
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- Citations: 30
Krausbeck F, Mendive-Tapia D, Thom AJW, et al., 2014, Choosing RASSCF orbital active spaces for multiple electronic states, COMPUTATIONAL AND THEORETICAL CHEMISTRY, Vol: 1040, Pages: 14-19, ISSN: 2210-271X
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- Citations: 23
Vacher M, Mendive-Tapia D, Bearpark MJ, et al., 2014, The second-order Ehrenfest method A practical CASSCF approach to coupled electron-nuclear dynamics, THEORETICAL CHEMISTRY ACCOUNTS, Vol: 133, ISSN: 1432-881X
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- Citations: 36
Vacher M, Bearpark MJ, Robb MA, 2014, Communication: Oscillating charge migration between lone pairs persists without significant interaction with nuclear motion in the glycine and Gly-Gly-NH-CH<sub>3</sub> radical cations, JOURNAL OF CHEMICAL PHYSICS, Vol: 140, ISSN: 0021-9606
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- Citations: 31
Mooney CRS, Parkes MA, Zhang L, et al., 2014, Competition between photodetachment and autodetachment of the 2<SUP>1</SUP>ππ* state of the green fluorescent protein chromophore anion, JOURNAL OF CHEMICAL PHYSICS, Vol: 140, ISSN: 0021-9606
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- Citations: 21
Thompson LM, Lasoroski A, Champion PM, et al., 2014, Analytical Harmonic Vibrational Frequencies for the Green Fluorescent Protein Computed with ONIOM: Chromophore Mode Character and Its Response to Environment, Journal of Chemical Theory and Computation, Vol: 10, Pages: 751-766, ISSN: 1549-9618
Jenkins S, Blancafort L, Kirk SR, et al., 2014, The response of the electronic structure to electronic excitation and double bond torsion in fulvene: a combined QTAIM, stress tensor and MO perspective, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 16, Pages: 7115-7126, ISSN: 1463-9076
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- Citations: 50
Mendive-Tapia D, Vacher M, Bearpark MJ, et al., 2013, Coupled electron-nuclear dynamics: Charge migration and charge transfer initiated near a conical intersection, JOURNAL OF CHEMICAL PHYSICS, Vol: 139, ISSN: 0021-9606
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- Citations: 63
Serapian SA, Bearpark MJ, Bresme F, 2013, The shape of Au<sub>8</sub>: gold leaf or gold nugget?, NANOSCALE, Vol: 5, Pages: 6445-6457, ISSN: 2040-3364
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- Citations: 42
Mendive-Tapia D, Lasorne B, Worth GA, et al., 2012, Towards converging non-adiabatic direct dynamics calculations using frozen-width variational Gaussian product basis functions, Journal of Chemical Physics, Vol: 137
Serrano-Pérez JJ, de Vleeschouwer F, de Proft F, et al., 2012, How the Conical Intersection Seam Controls Chemical Selectivity in the Photocycloaddition of Ethylene and Benzene, Journal of Organic Chemistry
Vreven T, Thompson LM, Larkin SM, et al., 2012, Deconstructing the ONIOM Hessian: Investigating Method Combinations for Transition Structures, Journal of Chemical Theory and Computation, Vol: 8, Pages: 4907-4914
van Thor JJ, Lincoln CN, Kellner B, et al., 2012, Ultrafast vibrational dynamics of parallel excited state proton transfer reactions in the Green Fluorescent Protein, VIBRATIONAL SPECTROSCOPY, Vol: 62, Pages: 1-6, ISSN: 0924-2031
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- Citations: 9
Serrano-Pérez JJ, Bearpark MJ, Robb MA, 2012, The extended S1/S0 conical intersection seam for the photochemical 2 + 2 cycloaddition of two ethylene molecules, Molecular Physics, Vol: 110, Pages: 2493-2501
Izmaylov AF, Mendive-Tapia D, Bearpark MJ, et al., 2011, Nonequilibrium Fermi golden rule for electronic transitions through conical intersections, Journal of Chemical Physics, Vol: 135
We consider photoinduced electronic transitions through conical intersections in large molecules. Starting from the linear vibronic model Hamiltonian and treating linear diabatic couplings within the second order cumulant expansion, we have developed a simple analytical expression for the time evolution of electronic populations at finite temperature. The derived expression can be seen as a nonequilibrium generalization of the Fermi golden rule due to a nonequilibrium character of the initial photoinduced nuclear distribution. All parameters in our model are obtained from electronic structure calculations followed by a diabatization procedure. The results of our model are found to agree well with those of quantum dynamics for a test set of systems: fulvene molecule, 2,6-bis(methylene) adamantyl cation, and its dimethyl derivative.
Izmaylov AF, Mendive-Tapia D, Bearpark MJ, et al., 2011, Nonequilibrium Fermi golden rule for electronic transitions through conical intersections, JOURNAL OF CHEMICAL PHYSICS, Vol: 135, ISSN: 0021-9606
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- Citations: 72
Li Q, Mendive-Tapia D, Paterson MJ, et al., 2010, A global picture of the S<sub>1</sub>/S<sub>0</sub> conical intersection seam of benzene, CHEMICAL PHYSICS, Vol: 377, Pages: 60-65, ISSN: 0301-0104
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- Citations: 54
Araujo M, Lasorne B, Magalhaes AL, et al., 2010, Controlling Product Selection in the Photodissociation of Formaldehyde: Direct Quantum Dynamics from the S<sub>1</sub> Barrier, JOURNAL OF PHYSICAL CHEMISTRY A, Vol: 114, Pages: 12016-12020, ISSN: 1089-5639
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- Citations: 30
Tokmachev AM, Boggio-Pasqua M, Mendive-Tapia D, et al., 2010, Fluorescence of the perylene radical cation and an inaccessible D<sub>0</sub>/D<sub>1</sub> conical intersection: An MMVB, RASSCF, and TD-DFT computational study, JOURNAL OF CHEMICAL PHYSICS, Vol: 132, ISSN: 0021-9606
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- Citations: 20
Tomasello G, Bearpark MJ, Robb MA, et al., 2010, Significance of a Zwitterionic State for Fulgide Photochromism: Implications for the Design of Mimics, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 49, Pages: 2913-2916, ISSN: 1433-7851
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- Citations: 51
Mendive-Tapia D, Lasorne B, Worth GA, et al., 2010, Controlling the mechanism of fulvene S<sub>1</sub>/S<sub>0</sub> decay: switching off the stepwise population transfer, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 12, Pages: 15725-15733, ISSN: 1463-9076
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- Citations: 44
Nunn ADG, Minns RS, Spesyvtsev R, et al., 2010, Ultrafast dynamics through conical intersections and intramolecular vibrational energy redistribution in styrene, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 12, Pages: 15751-15759, ISSN: 1463-9076
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- Citations: 21
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