Field-free molecular orientation with terahertz few-cycle pulses.

We demonstrate theoretically an efficient field-free orientation in LiH and LiCl driven by available terahertz few-cycle pulses (TFCPs). Exact results by numerically solving the time-dependent Schrodinger equation including the vibrational and rotational degrees of freedom are compared to the rigid-rotor approximation (RRA) as well as to the impulsive approximation (IA), and the effect of rotational-vibrational coupling on the both RRA and IA is examined in detail. We find that the current available TFCPs may overcome the technical limitation of terahertz half-cycle pulse for enhancing the field-free molecular orientation.