  Rearrangement of rotation-vibration energy bands in isolated molecules within
semi-quantum approach is characterized by delta-Chern invariants associated to
a local semi-quantum Hamiltonian valid in a small neighborhood of a degeneracy
point for the initial semi-quantum Hamiltonian and also valid in a small
neighborhood of a critical point corresponding to the crossing of the boundary
between iso-Chern domains in the control parameter space. For a full quantum
model, a locally approximated Hamiltonian is assumed to take the form of a
Dirac operator together with a specific boundary condition. It is demonstrated
that the crossing of the boundary along a path with a delta-Chern invariant
equal to $\pm1$ corresponds to the transfer of one quantum level from a
subspaces of quantum states to the other subspace associated with respective
positive and negative energy eigenvalues of the local Dirac Hamiltonian.
