  The honeycomb compound $\alpha$-RuCl$_3$ is widely discussed as a proximate
Kitaev spin-liquid material. This scenario builds on spin-orbit entangled $j =
1/2$ moments arising for a $t_{2g}^5$ electron configuration with strong
spin-orbit coupling $\lambda$ and a large cubic crystal field. The low-energy
electronic structure of $\alpha$-RuCl$_3$, however, is still puzzling. In
particular infrared absorption features at 0.30 eV, 0.53 eV, and 0.75 eV seem
to be at odds with theory. Also the energy of the spin-orbit exciton, the
excitation from $j = 1/2$ to 3/2, and thus the value of $\lambda$ are
controversial. Combining infrared and Raman data, we show that the infrared
features can be attributed to single, double, and triple spin-orbit excitons.
We find $\lambda$ = 0.16 eV and $\Delta$ =42(4) meV for the observed non-cubic
crystal-field splitting, supporting the validity of the $j= 1/2$ picture for
$\alpha$-RuCl$_3$. The unusual strength of the double excitation is related to
the underlying hopping interactions which form the basis for dominant Kitaev
exchange.
