  Silicon vacancies in silicon carbide (SiC) have been proposed as interesting
candidates for quantum technology applications such as quantum sensing and
quantum repeaters. SiC exists in many polytypes with different plane stacking
sequences, and in each polytype, the vacancies can occupy a variety of
different lattice sites. In this work, we characterize and identify the three
most important charged silicon vacancies in the 6H-SiC polytype. We record the
photoluminescence and continuous-wave optically detected magnetic resonance
spectra at different radio-frequency power levels and different temperatures.
We individually select the zero-phonon lines of the different silicon vacancies
at low temperatures and record the corresponding optically detected magnetic
resonance (ODMR) spectra. ODMR allows us to correlate optical and magnetic
resonance spectra and thereby resolve a controversy from earlier work.
