  A five-level four-pulse phase-sensitive extended stimulated Raman adiabatic
passage scheme is proposed to realize complete control of the population
transfer branching ratio between two degenerate target states. The control is
achieved via a three-node null eigenstate that can be correlated with an
arbitrary superposition of the target states. Our results suggest that complete
suppression of the yield of one of two degenerate product states, and therefore
absolute selectivity in photochemistry, is achievable and predictable, even
without studying the properties of the unwanted product state beforehand.
