The diagnostics of the radio-frequency (induction mode) plasma expanded through a nozzle (PETN) at low pressures (100-1000 Pa) was performed by on-line optical emission spectroscopy (OES) and on line quadrupole mass spectrometry (QMS). The OES was used for evaluating the electronic, vibrational, and rotational temperatures (T-e, T-v, and T-r) along the plasma reactor before and after the nozzle. The PETN gas mixtures analyzed were Ar + N-2, Ar + CO, and Ar + O-2 with an addition of 1 vol.% N-2 to the last two gas mixtures. For the same conditions in the PETN the values of T-e, T-v, and T-r were found to be different for the different gas mixtures and related to the depopulation of excited N-2(+) by oxygen atoms. Moreover the Ar + O-2 PETN aqueous solutions of lanthanum and manganese nitrates were nebulized for the deposition of LaMnO3 perovskite. The QMS, in real time, measuring the mass species formed before and after the nozzle, explained the reasons in the different values of T-e, T-v, and T-r for the three gas mixtures as well as for the formation of oxides in the PETN from the aqueous nitrate solutions.