Molecular beam mass spectrometry measurements of vibrationally excited N₂ in the effluent of an atmospheric plasma jet: a comparison with a state-to-state kinetic model

Vibrationally excited N₂ molecules are suggested to be one of the possible key species responsible for the observed synergistic effects in plasma catalysis for NH₃ synthesis. To assess the impact of vibrationally excited species in plasma-catalysis, quantitative measurements near interfaces are required, which remains challenging. In this letter, we report spatially resolved measurements of vibrationally excited N₂ in the effluent of an atmospheric pressure plasma jet by molecular beam mass spectrometry (MBMS). The mass spectrometry signals as a function of electron energy of the ionizer were fitted with the effective electron-impact ionization cross section of N₂(v) considering the vibrational distribution function as determined by a detailed vibrational level resolved plasma kinetic calculation. The reported method presented in this letter shows the capability of MBMS to measure vibrationally excited species of N₂ near interfaces when the vibrational distribution function is known or assumed and shows excellent agreement with state-to-state kinetic models of N₂(v).