Programme

O.6 -- Oral, NCTP-39

Date: Monday, 28-07-2014

Time: 16h00 - 16h20

Coherent Pi-Electron Rotations in a Nonplanar Chiral Aromatic Molecule

H. Mineo (1), S.H. Lin (1,2), and Y. Fujimura (3)

(1) Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan; (2) Department of Applied Chemistry, Institute of Molecular Science, Hsin-Chu 300, Taiwan; (3) Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan

The $\pi$ electrons in aromatic rings are considered to play an important role for organic electronics. Research on electrodynamics in molecular systems have been accelerated by recent developments of laser technology. There have also been theoretical studies of $\pi$-electron dynamics control in aromatic ring molecules by UV laser pulses. The $\pi$-electron ring current in Mg-porphyrin are induced by a few cycle of circularly polarized (CP) UV laser pulse. Here photon angular momentum is transferred to degenerated electronic excited states by circularly polarized laser pulse. The linearly polarized (LP) UV laser pulse is also used to create $\pi$-electron ring current in 2,5-dichloro[n](3,6) pyrazinophane, which is a chiral molecule and has no degenerate electronic excited states. The $\pi$-electron ring currents are created by coherent excitation of a pair of quasi-degenerate electronic excited states. In this work we use (P)-2,2’-biphenol, which is a typical nonplanar chiral aromatic molecule with axial chirality. The time-dependent coherent ring currents and angular momentum were calculated using the density matrix theory based on the LCAO MO approximation. The results of the numerical simulation of coherent-electron ring currents and angular momentum in (P)-2,2'-biphenol are shown. We also propose an ultrafast quantum switching method of $\pi$-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.

Presenter: Hirobumi Mineo