Unidirectional Electronic Ring Current Driven by a Few Cycle Circularly Polarized Laser Pulse: Quantum Model Simulations for Mg−Porphyrin

Abstract

A circularly polarized ultraviolet (UV) laser pulse may excite a unidirectional valence-type electronic ring current in an oriented molecule, within the pulse duration of a few femtoseconds (e.g., τ = 3.5 fs). The mechanism is demonstrated by quantum model simulation for |X〉 = |1 ¹A_1g〉 → |E₊〉 = |4 ¹E_u+〉 population transfer in the model system, Mg−porphyrin. The net ring current generated by the laser pulse (I = 84.5 μA) is at least 100 times stronger than any ring current, which could be induced by means of permanent magnetic fields, with present technology.