Driving a solution of optical isomer molecules with the resonant frequency What happens when we drive a solution of optical isomer molecules (enantiomers) with a microwave radiation in resonance with the tunneling frequency of the molecules (the frequency of the transition between the eigenstates of the Hamiltonian)?  I expect it will become a racemic mixture. Is that correct?
Update: Any reference for an experiment that does that is appreciated.
 A: Usually, optical isomers are defined when tunneling can be neglected (that is, when the torsional barrier between the isomers is very large that the isomers can be isolated and are considered stable). Then the ground state of the Hamiltonian is degenerate. From Quantum Mechanics it is a question of taste weather you choose the localized basis or the symmetric basis to define your states
$\psi_\pm = \psi_R \pm \psi_L$, where $\psi_{R/L}$ are the ground state eigenfunctions for the right/left isomers and $\psi_\pm$ are the symmetric (antisymmetric) eigenfunctions.
However, due to decoherence (and the process called einselection by Zurek) in fact the molecules in the ground states are described by the localized states (the isomer states). You can use a laser to drive the population from the ground state to an excited state with energy above the torsional barrier (or with large tunneling) and then wait for torsion to occur and then dump again the population to the ground state of the other isomer. Usually when you do this you move $\psi_R \leftrightarrow \psi_L$ so that if you start in a racemic mixture you end up in a racemic mixture, but if you start in a single isomer, you can convert to the other isomer. However, there are also procedures to "break" this symmetry. For references, see Shapiro et al, Phys. Rev. Lett. 84, 1669 (2000) and Phys. Rev. Lett. 90, 033001 (2003).
A: Your intuition is right, as far as your solution of optically active (chiral) molecules can be assimilated to an ensemble of harmonically driven two-level systems. For the two level system (left- and right handed molecules being the respective states) which starts out with only left handed molecules, the radiation drives the system to a state where left- and right handed molecules are present in proportion of 50%.
However, the fine tuning of the frequency is not important in reaching the final 50% distribution. A larger difference between the driving- and the eigenfrequency of the left-right transition leads only to a smoother, more prolonged transition to the final 50% state.
I cannot understand this by pure theory,  but numerical simulation shows this . 
