Field-free orientation dynamics of CO molecule by combining two-color shaped laser pulse with THz laser pulse train

•We propose a scheme to achieve field-free molecular orientation by two-color shaped laser pulse and THz laser pulse train.•Molecular positive and negative orientation degrees can be significantly enhanced by the combination of two-color shaped laser pulse and THz laser pulse train compared to the single THz laser pulse train.•An efficient molecular orientation can be obtained by the combination of two-color shaped laser pulse and THz laser pulse train with small pulse number N.•Molecular positive and negative orientation degrees are greater than 0.5 at T = 10 K.

Field-free orientation of CO molecule is studied theoretically by combining a nonresonant two-color shaped laser pulse with a time-delayed THz laser pulse train. The molecular positive and negative orientation degrees can be significantly enhanced by the combination of two-color shaped laser pulse and THz laser pulse train compared with the single THz laser pulse train. The effects of the pulse number of THz laser pulse train and the delay time between two-color shaped laser pulse and THz laser pulse train on molecular orientation are discussed. Further, the influence of the initial rotational temperature on molecular orientation is investigated. The maximal positive and negative orientation degrees obtained are 〈cos θ〉pmax = 0.91 and 〈cos θ〉nmax = 0.89, respectively.

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