Coherent control of molecular orientation

A coherent control scheme is proposed for the orientation of heteronuclear molecules by two-color phase-locked laser excitation. In the case of hexapole state-selected NO, a superposition of both negative and positive ground-state parity levels is formed, where the internuclear axis of the molecule is oriented along the laser polarization axis. The proposed scheme allows rotationally cold distributions of ground-state heteronuclear molecules to be macroscopically oriented, as in the "brute force" dc electric field orientation technique. Computer simulations show that for a typical ¹S ground-state diatomic molecule (B_rot = 0.32 cm^-1) picosecond two-color phase-locked laser excitation can provide orientation during or after the laser pulse.