Non-adiabatic molecular Hamiltonian: Canonical transformation coupling   electronic and vibrational motions
  The coupling of electronic and vibrational motion is studied by two canonical transformations namely normal coordinate transformation and momentum transformation on molecular Hamiltonian. It is shown that by these transformations we can pass from crude approximation to adiabatic approximation and then to non-adiabatic (diabatic) Hamiltonian. This leads to renormalized fermions and renormalized diabatic phonons. Simple calculations on $H_{2}$, $HD$, and $D_{2}$ systems are performed and compared with previous approaches. Problem of electronic quasi-degeneracy is discussed. 
Ivan Hubac, Peter Babinec, Martin Polasek, Jan Urban, Pavel Mach,   Jozef Masik, and Jerzy Leszczynski