  We construct an abstract pseudodifferential calculus with operator-valued
symbol, adapted to the treatment of Coulomb-type interactions, and we apply it
to study the quantum evolution of molecules in the Born-Oppenheimer
approximation, in the case where the electronic Hamiltonian admits a local gap
in its spectrum. In particular, we show that the molecular evolution can be
reduced to the one of a system of smooth semiclassical operators, the symbol of
which can be computed explicitely. In addition, we study the propagation of
certain wave packets up to long time values of Ehrenfest order. (This work has
been accepted for publication as part of the Memoirs of the American
Mathematical Society and will be published in a future volume.)
