PHYS 70 |
| A simple approach for numerically exact simulations of nonadiabatic quantum dynamics in multidimensional systems will be presented and applied to the description of the nonadiabatic quantum dynamics at conical intersections of electronic excited state potential energy surfaces. The photoabsorption spectroscopy of pyrazine and the cis/trans photoisomerization of retinal in rhodopsin will be discussed. The propagation scheme generalizes the recently developed Matching-Pursuit/Split-Operator-Fourier-Transform (MP/SOFT) method [Y. Wu and V. S. Batista, J. Chem. Phys. 121, 1676 (2004)] to simulations of nonadiabatic quantum dynamics [X. Chen and V. S. Batista J. Chem. Phys., 125, 124313, 2006]. The time-evolution operator is applied, as defined by the Trotter expansion to second order accuracy, in dynamically adaptive coherent-state expansions. These representations are obtained by combining the matching pursuit algorithm with a gradient-based optimization method. The accuracy and efficiency of the resulting computational approach are demonstrated in calculations of time-dependent survival amplitudes and photoabsorption cross-sections, using a model Hamiltonian that allows for direct comparisons with benchmark calculations. Simulations in full-dimensional potential energy surfaces involve the propagation of a 24-dimensional wavepackets. The reported results show that the generalized MP/SOFT method is a practical and accurate approach to model nonadiabatic reaction dynamics in polyatomic systems. |
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Excited Electronic States in Chemistry and Biology: Theory and Experiment
1:20 PM-4:50 PM, Sunday, August 19, 2007 BCEC -- 160A, Oral
Division of Physical Chemistry |