Unidirectional electronic ring current driven by a few cycle circularly polarized laser pulse: Quantum model simulations for Mg-porphyrin

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., tau - 3.5 fs). The mechanism is demonstrated by quantum model simulation for vertical bar X > = vertical bar 1 (1)A(1g)> -> vertical bar E+> = vertical bar 4 E-1(u+)> population transfer in the model system, Mg-porphyrin. The net ring current generated by the laser pulse (I = 84.5 AA) is at least 100 times stronger than any ring current, which could be induced by means of permanent magnetic fields, with present technology.