Laser manipulation of localised pi-electron rotations in a molecule with two aromatic rings

Abstract

Coherent dynamics of localised pi-electron rotations in an aromatic ring molecule may play an important role in designing next generation photo-induced organic molecular devices. In this paper, we present a theoretical study of laser control of localised pi-electron rotations in a low symmetry aromatic ring molecule, which are created by the coherence of two or more electronic excited states. The control scenario is to manipulate energy spacings between two electronic states by utilising AC Stark shift induced by strong non-resonant ultraviolet (UV) laser. We set three targets for laser manipulation of localised electron rotational dynamics for (P)-2,2'-biphenol with two aromatic rings. The first target is flipping of the direction of the localised pi-electron rotation on the same ring, the second one is the transfer of the pi-electron rotation localisation from one aromatic ring to the other, and the third one is freezing the unidirectional pi-electron rotation localised on one aromatic ring. We propose the fundamental principle of laser manipulation of localised pi-electron rotation utilising AC Stark shift. Expectation values of the localised electron angular momentum are calculated numerically to demonstrate our idea of laser manipulation. Effects of laser-field intensity on localised electron rotation dynamics are briefly discussed.