  We report the generation of a purely vibrational Raman comb, extending from
the vacuum ultraviolet (184 nm) to the visible (478 nm), in hydrogen-filled
kagom\'e-style photonic crystal fiber pumped at 266 nm. Stimulated Raman
scattering and molecular modulation processes are enhanced by higher Raman gain
in the ultraviolet. Owing to the pressure-tunable normal dispersion landscape
of the fiber-gas system in the ultraviolet, higher-order anti-Stokes bands are
generated preferentially in higher-order fiber modes. The results pave the way
towards tunable fiber-based sources of deep- and vacuum ultraviolet light for
applications in, e.g., spectroscopy and biomedicine.
