Selective preparation of enantiomers from a racemate by laser pulses: model simulation for oriented atropisomers with coupled rotations and torsions Original Research Article

We design a laser pulse which drives a racemate of oriented atropisomers at low temperature to a preferential target enantiomer. The overall laser pulse consists of a series of individual circularly polarized laser pulses which induce corresponding selective transitions between coupled rotational and torsional states. The underlying theory is derived in detail for a model system. It consists of two fragments which may carry out torsional and rotational motions around a molecular bond which is oriented along the direction of the laser pulses. Exemplarily, results are demonstrated for the model system H2POSH in the electronic ground state, based on a quantum chemical ab initio potential and on the components of the dipole functions describing the laser–dipole interaction. The series of laser pulses for the preparation of the pure enantiomers for this demanding system is based on analogous results for simpler scenarios, originally starting from local control.