Reconciling semiclassical and bohmian mechanics: IV. multisurface dynamics

In previous articles (J. Chem. Phys. 2004, 121, 4501 ; 2006, 124, 034115; 2006, 124, 034116)'a bipolar counterpropagating wave decomposition, Ψ = Ψ ₊ + Ψ _-, was presented for stationary states Ψ of the one-dimensional Schrödinger equation, such that the components Ψ _-approach their semiclassical WKB analogs in the large action limit. The corresponding bipolar quantum trajectories are classical-like and well-behaved, even when Ψ has many nodes or is wildly oscillatory. In this paper, the method is generalized for multisurface scattering applications and applied to several benchmark problems. A natural connection is established between intersurface transitions and (+ ↔ - ) transitions.