Landau-Zener problem for energies close to potential crossing points
  We examine one overlooked in previous investigations aspect of well - known Landau - Zener (LZ) problem, namely, the behavior in the intermediate, i.e. close to a crossing point, energy region, when all four LZ states are coupled and should be taken into account. We calculate the 4 x 4 connection matrix in this intermediate energy region, possessing the same block structure as the known connection matrices for the tunneling and in the over-barrier regions of the energy, and continously matching those in the corresponding energy regions. 
V.A.Benderskii, E.V.Vetoshkin (Institute of Problems of Chemical   Physics, Moscow Region, Chernogolovka, Russia), E. I. Kat...