  We report a systematic photoluminescence (PL) investigation of the spectral
emission properties of individual optical defects fabricated in diamond upon
ion implantation and annealing. Three spectral lines at 620 nm, 631 nm, and 647
nm are identified and attributed to the SnV center due to their occurrence in
the PL spectra of the very same single-photon emitting defects. We show that
the relative occurrence of the three spectral features can be modified by
oxidizing the sample surface following thermal annealing. We finally report the
relevant emission properties of each class of individual emitters, including
the excited state emission lifetime and the emission intensity saturation
parameters.
