On the Non‐Adiabatic Properties of Tunneling Centres

A non‐adiabatic formulation of the Hamiltonian for tunneling centres is given. A modified Born‐Oppenheimer basis is employed, which attaches the tunneling particle to a central reference coordinate. The non‐adiabatic dynamical lattice disturbance near the defect is established. New phonon assisted relaxation paths of a direct nature are exhibited. In Li+‐like centres these seem to be dominant, since the conventional ones are of pure non‐adiabatic origin (and of second order).