Field-free molecular orientation of1Σand2Πmolecules at high temperature

We analyze the control of field-free molecular orientation at high temperature by use of a two-color laser bipulse strategy proposed in Zhang et al. [Phys. Rev. A 83, 043410 (2011)]. A general study shows that there exist two types of linear molecules for which a different mechanism has to be used. For molecules with a large hyperpolarizability, a monochromatic laser pre-pulse is applied before the two-color laser pulse at a time close to the rotational period ${T}_{r}$, while for molecules with a small hyperpolarizability, the optimal delay is found close to ${T}_{r}/4$ or $3{T}_{r}/4$. We extend this analysis to the case of a ${}^{2}\phantom{\rule{-0.16em}{0ex}}\ensuremath{\Pi}$ molecule …