From now on, the term "trajectory" will denote a set of 3N n nuclear coordinates that evolve in time, and all quantities in the quantum formulation that depend on R will depend on the trajectory R α (t), with α indexing the trajectories. When the electronic wavefunction ϕ(r, t; R α (t)) is expressed as a linear combination of adiabatic states, φ (m) (r, t; R α (t)), their parametric dependence on the nuclear position/trajectory induces an implicit time dependence. The expansion coefficients in