Trajectory-based methods for the study of ultrafast quantum dynamics

Abstract

Introduction. We developed and implemented novel methods for the computer simulation of ultrafast quantum dynamics in molecular systems, which were subsequently applied in the investigation of a wide variety of photoinduced dynamical processes in atoms, molecules and solids. Methods. The new methodology maps the dynamics of the original quantum system into that of an equivalent classical system with larger dimensionality. The resulting equations of motion were integrated numerically using algorithms with adaptive time step. The computed observables were compared with the results obtained via wavepacket propagation. Results and discussion. The methodology reproduces paradigmatic quantum effects such as zero-point energy, tunnel effect and quantum interference; its accuracy and numerical efficiency surpasses those of alternative computational tools available nowadays. It accounts correctly for phenomena as diverse as the photoionization of an atom by an ultrashort laser pulse, the vibrational predissociation of van der Waals complexes, the electron dynamics in quantum dots and the photoexcitation of alkali metal atoms in rare gas matrices. Conclusions. It was concluded that the simulation of the quantum dynamics of atoms, molecules and solids has shown that the predictions of the interacting trajectory propagation scheme are in excellent agreement with the observables calculated from the direct solution of the Schrödinger equation, and with the available experimental data. Additionally, the method provides an intuitive representation of the dynamical processes, since the trajectories follow the flux lines of the quantum probability density.