  Photoionization calculations of the endofullerene molecule Cl@$C_{60}$ with
an open-shell chlorine atom are performed in the time-dependent local density
approximation (TDLDA) based on a spherical jellium model. Cross sections for
atom-fullerene hybrid photoemission studied show the effects of the
hybridization symmetry, the giant plasmon and the molecular cavity. Comparisons
with the results of Ar@$C_{60}$ provide insights in the role of a shell-closing
electron and its influence on the dynamics. The results for Cl@$C_{60}$ are
further compared with those of a more stable, lower energy configuration that
results after a $C_{60}$ electron transfers to Cl forming Cl$^-$@$C_{60}^+$.
This comparison reveals noticeable differences in the ionization properties of
the antibonding hybrid state while the bonding hybrid remains nearly unaltered
showing a magnification covering the entire giant plasmon energy range.
