There
are multiple active species at the interface between the
discharged gas phase and the water phase. Activated nitrogen species
are generated in the nitrogen plasma gas by dielectric barrier discharge
(DBD). The reaction at the interface between the gas phase containing
the activated nitrogen species and water phase (P/L reaction) can
produce nitrogen-derived compounds (N-compounds) in water. We have
already clarified the mechanism of the P/L reaction focusing on highly
active atomic nitrogen in a previous study. In this study, we report
the mechanism of the P/L reaction by excited but metastable nitrogen
molecules. Involving excited nitrogen molecules [N2(A3Σu
+)] with a long lifetime, the
reaction selectivity of N-compounds was clarified by quantitative
analysis. Moreover, the active species in the water phase (H·,
HO·, H2O2) of the P/L reaction were measured,
and the involvement of the reaction in the generation of N-compounds
was confirmed. The findings clarify that each activated nitrogen species
reacts differently with H2O. These results suggest that
the occurrence of either an oxidation reaction or a reduction reaction
can be regulated by controlling the activated nitrogen species.