Nitrogen doping of ZnSe MBE layers is studied using two original nitrogen activators which controllably produce output beams with different partial content of an atomic nitrogen (N) and metastable electronically excited molecules (N-2*). The most electrically stable doping with a net acceptor concentration up to 5 x 10(17) cm(-3) is achieved by an RF capacitively coupled magnetron activator in the regimes corresponding to maximal partial concentration of N-2* while a dominance of N, typical for DC discharge with a vacuum anode sheath, results in the electrical instability of the doping parameters. Low-temperature photoluminescence spectra reveal DAP bands related to shallow and deep donor levels, where the intensities strongly depend on the partial composition of the activator output beam. The results demonstrate that N-2*selective dissociative adsorption at a Zn atom is a favourable p-type doping beam. The results demonstrate atomic nitrogen, although providing a similar net acceptor concentration, appears to be responsible also for the unstable atomic nitrogen, although providing a similar net acceptor concentration, appears to be responsible also for the unstable shallow donor center. A (100) split interstitial complex is considered as the most probable candidate for this donor.