Density-matrix-spectroscopic algorithm for excited-state adiabatic surfaces and molecular dynamics of a protonated Schiff base

Excited-state potentials of a short protonated Schiff base cation which serves as a model for the photoisomerization of retinal are computed by combining a semi-empirical ground-state adiabatic surface with excitation energies obtained using the time-dependent coupled electronic oscillator (CEO) approach. Excited-state molecular dynamic simulation of the in-plane motion of cis-C5H6NH2+ following impulsive optical excitation reveals a dominating 1754 cm−1 π-conjugation mode. A new molecular dynamics algorithm is proposed which resembles the Car–Parinello ground-state technique and is based on the adiabatic propagation of the ground-state single-electron density matrix and the collective electronic modes along the trajectory.