Speaker
Description
The standard Born-Oppenheimer approach to theoretical treatments of inelastic collision processes is the most widely used approach, despite many other methods have been proposed as well. It solves the problems into two steps: (1) the electronic structure calculations for fixed nuclei, and (2) nonadiabatic nuclear dynamical studies based on the potentials and couplings computed at the first step. Various quantum methods have been developed for the both steps and applied to a large variety of collisional partners (atoms, ions, molecules, clusters, etc) and to a huge number of physical processes. The approach looks to be well developed and reliable.
However, the detailed analysis shows that the conventional applications of the Born-Oppenheimer approach encounter severe problems. They are: ambiguity of nonadiabatic couplings and coupled channel equations, nonvanishing asymptotic nonadiabatic couplings, divergence of state-to-state transition probabilities and cross sections with respect to some parameters of problems, to mention a few. The most severe is probably nonzero asymptotic couplings. In the past, these and other problems have been ignored as being negligible, and final results (transition probabilities, cross sections, rate coefficients) were assumed to have low error bars, since usual practical calculations were performed with a number of approximations. The development of modern computer facilities and soft wear allow one to increase accuracy of calculations. Nevertheless, Ref. [1] shown that attempts to extend parameters of calculations within the conventional application of the Born-Oppenheimer approach result in divergence instead of expected convergence, and the results have no sense.
The reprojection method [1-3] within the standard Born-Oppenheimer approach solves the problems. It treats the nonadiabatic nuclear dynamics with nonzero asymptotic nonadiabatic coupligs, as they come from ab initio electronic structure calculations. In addition, the method distinguishes interatomic and internuclear distances, as well as the scattering channels and molecular states. It turns out that the nonzero asymptotic couplings are responsible for correct asymptotic wave functions. Moreover, Ref. [4] shows that the correct asymptotic wave functions can be constructed from the coupled asymptotic solutions of the dynamical equations.
- A. K. Belyaev, Phys. Rev. A 82, 060701 (2010).
- J. Grosser, T. Menzel, and A. K. Belyaev, Phys. Rev. A. 59, 1309 (1999).
- A. K. Belyaev, D. Egorova, J. Grosser, and T. Menzel, Phys. Rev. A 64, 052701 (2001).
- С. Л. Яковлев, Е. А. Яревский, Н. Эландер и А. К. Беляев, ТиМФ 195, 437 (2018).
| The speaker is a student or young scientist | No |
|---|---|
| Section | 1. Nuclear structure: theory and experiment |
