Charge migration following ionization in systems with chromophore-donor and amine-acceptor sites

Abstract

The ultrafast charge migration following outer-valence ionization in three different but related molecules, namely, 2-phenylethyl-$N,N$ -dimethylamine (PENNA), and its butadiene (MePeNNA) and ethylene (BUNNA) derivates, is studied in detail. The molecules have different chromophore-donor sites, but nearly identical amine-acceptor sites. The results show that the charge migration process depends strongly on the particular donor site, varying from ultrafast migration of the charge from the donor to the acceptor site ($4\mathrm{fs}$ for MePeNNA) to no migration at all (for BUNNA). The influence of the geometrical structure of the molecule on the charge migration is also investigated. It is shown that energetically closely lying conformers may exhibit dramatically different charge migration behaviors. The basic mechanism of the charge migration process in the studied molecules is analyzed in detail and is demonstrated to be due to electron correlation and relaxation effects.