  We perform quantum logic spectroscopy with a $^{27}$Al$^{+}$/$^{40}$Ca$^{+}$
mixed ion crystal in a linear Paul trap for a measurement of the
$(3s^{2})\,^{1}\mathrm{S}_{0} \leftrightarrow \, (3s3p)\,^{3}\mathrm{P}_{1},
F=7/2$ intercombination transition in $^{27}$Al$^{+}$. Towards this end, Ramsey
spectroscopy is used for probing the transition in $^{27}$Al$^{+}$ and the
$(4s^{2})\,\mathrm{S}_{1/2} \leftrightarrow \, (4s3d)\,\mathrm{D}_{5/2}$ clock
transition in $^{40}$Ca$^{+}$ in interleaved measurements. By using the
precisely measured frequency of the clock transition in $^{40}$Ca$^{+}$ as a
frequency reference, we determine the frequency of the intercombination line to
be $\nu_{^{1}\mathrm{S}_{0} \leftrightarrow \,^{3}\mathrm{P}_{1},F=7/2}$=1122
842 857 334 736(93) Hz and the Land\'e g-factor of the excited state to be
$g_{^{3}\mathrm{P}_{1}, F=7/2}$=0.428132(2).
