A study of the annealing processes and charge state of dilute Fe in rutile TiO 2 single crystals was performed in the temperature range 143–662 K, utilizing online 57 Fe emission Mössbauer spectroscopy following low concentrations (< 10− 3 at%) implantation of 57 Mn (T 1/2= 1.5 min). Both Fe 3+ and Fe 2+ were detected throughout the temperature range. Three annealing stages were distinguished:(i) a broad annealing stage below room temperature leading to an increased Fe 3+ fraction;(ii) a sharp annealing stage at~ 330 K characterized by conversion of Fe 3+ to Fe 2+ and changes in the hyperfine parameters of Fe 2+, attributed to the annealing of Ti vacancies in the vicinity of the probe atoms; and (iii) an annealing stage in the temperature range from 550 to 600 K, where all Fe ions are transformed to Fe 3+, attributed to the annealing of the nearby O vacancies. The dissociation energy of Mn Ti–V O pairs was …