P m n ( t , t + Δ t ) ≡ ρ m m ( t ) − ρ m m ( t + Δ t ) ρ m m ( t ) c ( t + Δ t ) = exp ( − i E Δ t / ℏ ) Γ ( t , t + Δ t ) c ( t )
Δ t
Numerical problems due to the (near) divergence of the nonadiabatic coupling tensor elements are circumvented here, thus allowing much longer time steps than in Tully's traditional FSSH-1.
Light Particle Nonadiabatic Probability 2
FSSH-2 probability for a nonadiabatic transition of the light particle(s) subsystem, induced by the heavy particle(s) dynamics