  The class of ultra-hot Jupiters comprises giant exoplanets undergoing intense
irradiation from their host stars. They have proved to be a particularly
interesting population for their orbital and atmospheric properties. One such
planet, WASP-121~b, is in a highly misaligned orbit close to its Roche limit,
and its atmosphere exhibits a thermal inversion. These properties make
WASP-121~b an interesting target for additional atmospheric characterization.
In this paper, we present analysis of archival high-resolution optical spectra
obtained during transits of WASP-121~b. Artifacts from the Rossiter-McLaughlin
effect and Center-to-Limb Variation are deemed negligible. However, we discuss
scenarios where these effects warrant more careful treatment by modeling the
WASP-121 system and varying its properties. We report a new detection of
atmospheric absorption from H$\alpha$ in the planet with a transit depth of
$1.87\pm0.11\%$. We further confirm a previous detection of the Na I doublet,
and report a new detection of Fe I via cross-correlation with a model template.
We attribute the H$\alpha$ absorption to an extended Hydrogen atmosphere,
potentially undergoing escape, and the Fe I to equilibrium chemistry at the
planetary photosphere. These detections help to constrain the composition and
chemical processes in the atmosphere of WASP-121~b.
