Enhancement of molecular field-free orientation by utilizing rovibrational excitation

We have demonstrated that field-free molecular orientation induced by a terahertz half-cycle pulse can be considerably enhanced by rovibrational selective excitation. The excitation process is controlled by infrared laser pulses. The calculations are performed by solving numerically the full time-dependent Schrِdinger equation for the HF molecule including molecular rovibrational degrees of freedom at finite rotational temperature. The effect of molecular structure on the field-free orientation is discussed by comparing HF with LiH molecules.