Theoretical Study of Coherent π-Electron Rotations in a Nonplanar Chiral Aromatic Molecule Induced by Ultrafast Linearly Polarized UV Pulses

Abstract

We present the results of a theoretical study of π-electron dynamics in a nonplanar chiral aromatic molecule (P)-2,2′-biphenol. Coherent ring currents, which are one of the main observables of coherent π-electron dynamics, are generated by applying the linearly polarized UV pulse laser, where a pair of coherent quasi-degenerated excited states is created. In this paper we review the formulations of the time-dependent coherent ring currents and angular momentum which were obtained using the density matrix theory based on the LCAO MO approximation. The results of the numerical simulation of coherent π-electron ring currents and angular momentum in (P)-2,2′-biphenol are shown. We also propose an ultrafast quantum switching method of π-electron rotations and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses with properly selected laser polarizations, time delay and relative phases. Finally we refer to an outline for the extension of our method to N aromatic rings chain (N ≥ 3).