Nonadiabatic scattering of a quantum particle in an inhomogenous magnetic field

We investigate the quantum effects, in particular the Landau-level quantiza tion, in the scattering of a particle, the nonadiabatic classical dynamics of which is governed by an adiabatic invariant. As a relevant example, we s tudy the scattering of a drifting particle on a magnetic barrier in the qua ntum limit where the cyclotron energy is much larger than a broadening of t he Landau levels induced by the nonadiabatic transitions. We find that, des pite the level quantization, the exponential suppression exp [-2 pid/delta] (barrier width d, orbital shift per cyclotron revolution delta) of the roo t-mean-square transverse displacement experienced by the particle after the scattering is the same in the quantum and the classical regime.