Laser-induced steric effects in nonlinear processes from short laser pulses

The response of st diatomic or symmetric-top molecule in a nonlinear optical process through its third-order susceptibility is investigated in terms of the internuclear axis orientation and the plane of molecular rotation. The effect of the spatial arrangement of the molecular system in a Raman-type or two-photon absorption-type intermediate resonance is studied for laser pulses having a time-duration shea compared to a simple molecular rotation. We observe strong steric effects on the internuclear axis angular distribution depending drastically on the resonant rotational structure and on the incident polarizations.