The influence of vibrational excitation of NO+(X-1 Sigma(+):nu '') on the formation of NO* by the NO++C6F6- neutralization reaction at thermal energy

The NO(A(2)Sigma(+)-X(2)Pi r, C(2)Pi(r)-X(2)Pi(r), D(2)Sigma(+)-X(2)Pi(r)) emissions resulting from the mutual ion-ion neutralization reaction between NO+(X(1)Sigma(+)) and C6F6- have been measured at various source gas press ures of NO+ in a flowing afterglow in order to examine the influence of vib rational excitation in NO+(X :nu"). N2O was used as a source gas of NO+(X). The NO(A-X, C-X, D-X) emissions from only the nu' = 0 level were observed at high N2O pressures above ca. 60 mTorr (1 Torr = 133.322 Pa), where only NO+(X: nu" = 0) was present. On the other hand, the NO(A-X) emission from n u' = 1, 2 and the NO(D-X) emission from nu' = 1 appeared at low N2O pressur es below ca. 60 mTorr, where NO+(X:nu" > 0) was present. It was found that vibrational excitation in NO+(X : nu") results in vibrational excitation of the product NO(A, D : nu' = nu") molecule because of favorable Franck-Cond on factors for the NO+(X: nu") --> NO(A, D: nu' = nu") neutralization. The fact that the vibrational excitation of NO(D) is slightly higher than that of NO(A) indicated that the relative coupling strength between NO+(X: nu" > 0) + C6F6- and NO(D : nu' = nu") + C6F6 to that between NO+(X: nu" = 0) C6F6- and NO(D : nu' = 0) + C6F6 is larger than that in the corresponding p rocesses leading to NO(A: nu' = nu"). The lack of vibrational excitation of NO(C) was explained by the predissociation of NO(C : nu' > 0).