  Two molecules are enantiomers if they are non-superimposable mirror images of
each other. Electric dipole-allowed cyclic transitions
$|1\rangle\to|2\rangle\to|3\rangle\to|1\rangle$ obey the symmetry relation
$\mathcal{O}^{R}=-\mathcal{O}^{S}$, where
$\mathcal{O}^{R,S}=(\mu_{21}^{R,S}E_{21})(\mu_{13}^{R,S}E_{13})(\mu_{32}^{R,S}E_{32})$,
and $R,S$ label the two enantiomers. Here we generalize the concept of
topological frequency conversion to an ensemble of enantiomers. We show that,
within a rotating-frame, the pumping power between fields of frequency
$\omega_{1}$ and $\omega_{2}$ is sensitive to enantiomeric excess,
$\mathcal{P}_{2\to1}=\hbar\frac{\omega_{1}\omega_{2}C_{L}^{R}}{2\pi}(N_{R}-N_{S})$,
where $N_{i}$ is the number of enantiomers $i$ and $C_{L}^{R}$ is an
enantiomer-dependent Chern number. Connections with chiroptical microwave
spectroscopy are made. Our work provides an underexplored and fertile
connection between topological physics and molecular chirality.
