A nuclear trajectory, indicated with the symbol R α (t), is intended as a collection of 3N n positions that evolve in time. When the electronic wavefunction Φ(r, t; R α (t)) is expressed as a linear combination of adiabatic states, ϕ (m) (r; R α (t)), their parametric dependence on the nuclear position/trajectory induces an implicit time dependence. The expansion coefficients in Φ(r, t;