Formation of the CN(B 2Σ +) fragment from HCN in a discharged helium flow

Abstract

The CN(B 2Σ +-X 2Σ +) emission produced from HCN in collision with He(2 3S) was obtained by eliminating the influence of other active species in a discharged flow, and the vibrational and rotational energy distributions of thw CN(B 2Σ +) fragment were measured. The average vibrational and rotational energies were found to be 0.21 ± 0.08 and 0.12 ± 0.04 eV, respectively. It is shown by consideration of the energetics that the main process which produces this emission is the formation of CN(B 2Σ +) and H( n = 2) through the autoionizing Rydberg manifold which converges to HCH + ( 2Σ +).