The fluxes of ions and neutral sputtered particles incident at the growth surface during the deposition of TiN by reactive magnetron sputtering from a Ti target in mixed Ar+N2 discharges were determined using a combination of in situ double-modulation mass spectrometry, Langmuir probe, discharge, deposition rate, and film composition measurements. The N2 fraction f(N2) in the discharge was varied from 0 to 1 with the total pressure maintained at 3 mTorr (0.4 Pa). Target nitridation, observed directly through the detection of sputter-ejected TiN molecules, was found to occur over the narrow f(N2) range between congruent-to 0.035 and 0.06. With f(N2) <0.1, more than 94% of the ion flux incident at the substrate is Ar+ while for pure N2 discharges, N2+ accounts for more than 95% of the incident ions. Both the incident Ar+ and N2+ ion fluxes are highly monoenergetic with energies corresponding to eV(s), where V(s) is the applied negative substrate bias with respect to the plasma potential. However, the energy distributions of incident Ti+ and N+ ions are extended due to the high-energy tails in their sputter-ejection energy distributions. The primary sputter-ejected particles are Ti and N atoms. TiN, TiN+, and Ti+ do not contribute significantly to film growth kinetics.