open access

https://hdl.handle.net/2115/44992

Quantum reaction boundary to mediate reactions in laser fields

英語

2011-01-14

American Institute of Physics

Journal of Chemical Physics

134(2)

024317

Dynamics of passage over a saddle is investigated for a quantum system under the effect of time-dependent external field (laser pulse). We utilize the recently developed theories of nonlinear dynamics in the saddle region, and extend them to incorporate both time-dependence of the external field and quantum mechanical effects of the system. Anharmonic couplings and laser fields with any functional form of time dependence are explicitly taken into account. As the theory is based on the Weyl expression of quantum mechanics, interpretation is facilitated by the classical phase space picture, while no "classical approximation" is involved. We introduce a quantum reactivity operator to extract the reactive part of the system. In a model system with an optimally controlled laser field for the reaction, it is found that the boundary of the reaction in the phase space, extracted by the reactivity operator, is modulated with time by the effect of the laser field, to "catch" the system excited in the reactant region, and then to "release" it into the product region. This method provides new insights in understanding the origin of optimal control of chemical reactions by laser fields.

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Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in J. Chem. Phys. 134, 024317 (2011) and may be found at https://dx.doi.org/10.1063/1.3528937

0021-9606