Molecular dynamics investigations of photoinduced transformations in organic molecules

Abstract

A computer simulation procedure is developed for modeling intramolecular dynamics in polyatomic molecules. Electronic-vibrational excitation by ultrashort laser pulses (20 fs divided by 1 ps) is treated explicitly using quantum theory in harmonic approximation. MD simulation is used for studying the excited state dynamics. Stilbene photoinduced isomerization is modeled. Model potential energy surfaces (PES) for the ground and first excited singlet states are obtained using experimental absorption spectra in supersonic jet. Using a symmetrical along the torsional coordinate PES, it is shown that cis-stilbene undergoes the first stage of the isomerization reaction, i.e. transition to the twisted configuration, much faster than trans- stilbene, only due to the specific conformational properties.