Field-free molecular orientation by two-color femtosecond laser pulse and time-delayed THz laser pulse

We propose a scheme for achieving molecular orientation steered by the combination of a nonresonant two-color femtosecond laser pulse and a time-delayed THz laser pulse. It is shown that the molecular negative and positive orientation can be significantly enhanced by applying this scheme compared to the single femtosecond or THz laser pulse. The effects of the intensity of the two-color femtosecond laser pulse and the delay time between the femtosecond laser pulse and the THz laser pulse on molecular orientation are discussed. The molecular orientation also depends on the carrier-envelope phase of the THz laser pulse and the initial rotational temperature of the molecule. The maximal negative and positive orientation degrees calculated are < cos theta >(nmax) = 0.828 and < cos theta >(pmax) = 0.755, respectively.