Semiclassical quantization of bound and quasi-stationary states beyond the adiabatic approximation

TL;DR

This paper develops semiclassical quantization rules for crossing diabatic potentials in the Landau-Zener problem, accounting for complex state couplings relevant to molecular spectroscopy beyond the adiabatic approximation.

Contribution

It introduces a novel semiclassical quantization approach for coupled diabatic potentials considering all four adiabatic states in the intermediate energy region.

Findings

Derived quantization rules applicable to non-rigid molecules.

Extended semiclassical analysis beyond the adiabatic approximation.

Applicable to spectroscopy of molecules with multiple stable configurations.

Abstract

We examine one important (and overlooked in all previous investigations) aspect of well - known crossing diabatic potentials or Landau - Zener (LZ) problem. We derive the semiclassical quantization rules for the crossing diabatic potentials with localized initial and localized or delocalized final states, in the intermediate energy region, when all four adiabatic states are coupled and should be taken into account. In fact these situations exhaust all cases practically relevant for spectroscopy of non-rigid molecules (i.e. with more than one stable configuration).