Transport characteristics of N₂(A³Σ⁺_u), N(⁴S°), and N(²D°) in a remote nitrogen plasma source

We measured absolute densities of N₂(A³Σ⁺_u), N(⁴S°), and N(²D°) in the downstream region at various distances from a microwave N₂ plasma source. As a result, it was found that the transport of N(⁴S°) was highly efficient with keeping the densities on the order of 10¹⁷ m⁻³ at distances up to 12 cm from the discharge region. On the other hand, the densities of N₂(A³Σ⁺_u) and N(²D°) decayed from 10¹⁶ to 10¹⁴ m⁻³ when the distance between the discharge region and the measurement position was lengthened from 6 to 12 cm. The decay curves of the N₂(A³Σ⁺_u) and N(²D°) densities were different each other. The densities of N₂(A³Σ⁺_u) and N(²D°) in the downstream region were not owing to the transports but were due to their productions. We discussed the dominant production processes of N₂(A³Σ⁺_u) and N(²D°) on the basis of the experimental observations.