Selective photochemistry via adiabatic passage: degenerate product states with different lifetimes

Two-pulse selective photochemistry that exploits population transfer via adiabatic passage is considered for the case that there are degenerate product states with different lifetimes. As an example, a four-level model system with a complex symmetric Hamiltonian is constructed. Analytical and numerical studies of this model system demonstrate that extensive control over the product branching ratio can be achieved by detuning either the pump pulse or the Stokes pulse while maintaining negligible population in the intermediate state. This control approach represents a significant simplification of both the Kobrak-Rice extended stimulated Raman adiabatic passage scheme and the Chen-Shapiro-Brumer strong-field control scheme.