Optimal Enantioselective Orientation of Chiral Molecules Excited by Femtosecond Laser Pulses

The separation and discrimination of chiral enantiomers play an important role in various chemical, physical, and biological processes. To achieve chiral discrimination, enantioselective orientation induced by a pair of delayed cross-polarized femtosecond laser pulses has been recently proposed. However, no experiments have been implemented so far, partly due to the concerns that the required high-intensity pulses would result in non-negligible molecular ionization. In this work, we present a comprehensive study of the dependence of the induced enantioselective orientation on laser parameters. The enantioselective orientation is nearly proportional to the laser pulse energy at nonzero finite temperature and the optimal time delay corresponds to the moment of the maximum alignment induced by the first laser pulse. On the other hand, at zero temperature, the enantioselective orientation shows a complicated dependence on the laser parameters, including the laser pulse energy and time delay. We show that by optimizing the parameters, a significant (~ 10%) degree of enantioselective orientation can be achieved both at zero and  5 Kelvin of the rotational temperature. This study identifies realistic laser parameters for inducing the strong enantioselective orientation, which will, hopefully, stimulate experimental demonstration of the effect. The strong enantioselective orientation may be useful for enantiomeric excess analysis, as well as for enantioselective separation using inhomogeneous fields.