Abstract
We perform an electronic and nuclear flux analysis for nonadiabatic dynamics and its corresponding adiabatic counterpart, both of the wavefunctions of which are represented in the Born-Huang expansion. It is well known that the electronic-nuclear configurations (terms) in the expansion of the total wavefunction interfere each other through the nonadiabatic interactions and give birth to electronic and nuclear fluxes. Interestingly, even in the adiabatic dynamics without such nonadiabatic interactions, a wavefunction composed of more than one adiabatic state can undergo interference among the components and give the electronic and nuclear fluxes. That is, the individual pieces of the wavepacket components associated with the electronic wavefunctions in the adiabatic representation can propagate in time independently with no nonadiabatic interaction, and yet they can interfere among themselves to generate the specific types of electronic and nuclear fluxes. We refer to the dynamics of this class of total wavefunction as multiple-configuration adiabatic Born-Huang dynamics. A systematic way to distinguish the electronic and nuclear fluxes arising from nonadiabatic and the corresponding adiabatic dynamics is discussed, which leads to the deeper insight about the nonadiabatic dynamics and quantum interference in molecular processes. The so-called adiabatic flux will also be discussed.
Highlights
Nonadiabatic transition is one of the key phenomena in molecular science in which chemical and physical properties of molecules can undergo sudden change during the dynamical processes
We have presented an electronic and nuclear flux analysis on the nonadiabatic dynamics in comparison with the corresponding adiabatic dynamics of a wavefunction that is of multiple configuration in the Born-Huang representation
We have shown both theoretically and numerically that only the indirect nuclear flux Jenlu(r, R, t) and its reduced fluxes give a clear-cut distinction between the two dynamics, since Jenlu(r, R, t) is zero for any kind of adiabatic dynamics
Summary
Nonadiabatic transition is one of the key phenomena in molecular science in which chemical and physical properties of molecules can undergo sudden change during the dynamical processes. [In the Appendix, we briefly summarize the flux arising from the Ab Initio Molecular Dynamics (ABMD) and the semiclassical Ehrenfest theory (SET) since these are among the most frequently applied methods in the analysis of chemical reactions.] Matsuzaki and Takatsuka have recently applied a full flux analysis for a wavepacket bifurcation process due to the nonadiabatic interactions in the Born-Huang representation by calculating both the electronic and nuclear fluxes They first prepared a single nuclear Gaussian wavepacket at a Franck-Condon region on the first excited potential energy curve of LiF in the adiabatic representation and let it proceed towards the avoided crossing numerically. This section is complementary to the literature, for example, Refs. 20, 22, 23, and 36, and a particular emphasis is placed on the distinction between the fluxes arising from a nonadiabatic wavefunction and the corresponding multiple-configuration adiabatic function
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