Curve crossing in linear potential grids: The quasidegeneracy approximation - art. no. 043404

The quasidegeneracy approximation [V. A. Yurovsky, A. Ben-Reuven, P. S. Jul ienne, and Y. B. Band, J. Phys. B 32, 1845 (1999)] is used here to evaluate transition amplitudes for the problem of curve crossing in linear potentia l grids involving two sets of parallel potentials. The approximation descri bes phenomena, such as counterintuitive transitions and saturation (incompl ete population transfer), not predictable by the assumption of independent crossings. Also, a new kind of oscillations due to quantum interference (di fferent from the well-known Stuckelberg oscillations) is disclosed, and its nature discussed. The approximation can find applications in many fields o f physics, where multistate curve crossing problems occur.