How electronic superpositions drive nuclear motion following the creation of a localized hole in the glycine radical cation

In this work we have studied the nuclear and electron dynamics in the glycine cation starting from localized hole states, using the Quantum Ehrenfest (QuEh) method. The nuclear dynamics is controlled both by the initial gradient and by the instantaneous gradient that results from the oscillatory electron dynamics (charge migration). We have used the Fourier transform (FT) of the spin densities to identify the normal modes of the electron dynamics. We observe an isomorphic relationship between the electron dynamics normal modes (ED-NM) and the nuclear dynamics, seen in the vibrational normal modes (Vib-NM). The FT spectra obtained this way show bands that are characteristic of the energy differences between the adiabatic hole states. These bands contain individual peaks that are in one-to-one correspondence with atom pair (+ •) ↔(• +) resonances (APR), which in turn stimulate nuclear motion involving the atom pair. With such understanding we anticipate 'designer' coherent superpositions that can drive nuclear motion in a particular direction