  Using resonant two-step laser excitation of trapped $^{232}\mathrm{Th}^+$
ions, we observe 166 previously unknown energy levels of even parity within the
energy range from 7.8 to 9.8 eV and angular momenta from $J=1/2$ to $7/2$. We
also classify the high-lying levels observed in our earlier experiments by the
total angular momentum and perform ab-initio calculations to compare their
results with the observed level density. The observed levels can be relevant
for the excitation or decay of the $^{229m}\mathrm{Th}$ isomeric nuclear state
which lies in this energy range. The high density of electronic levels promises
a strongly enhanced electronic bridge excitation of the isomer in
$^{229}\mathrm{Th}^+$.
