Isotopic study of the intermolecular versus intramolecular energy transfer in the N2(<i>W</i>,<i>A</i>)+N2(<i>X</i>) reactions

Abstract

The energy transfer from the long-lived states N2(W 3Δu, A 3Σ+u) to the radiating state N2(B 3Πg) in collisions with N2(X 1Σ+g) was studied under single collision conditions, employing a molecular beam/target gas cell arrangement. By means of using the isotopic species 14N2 in the metastable reactant beam and 15N2 in the target gas cell it was possible to differentiate between the intramolecular and the intermolecular energy transfer mechanisms, on the basis of well-resolved N2(B) product emission spectra. The overall contributions of the two reaction channels were found to be comparable, but they differ greatly in the vibrational product distributions. The intermolecular process populates preferentially the low vibrational levels of 15N2(B,v). The intramolecular process is most efficient for those 14N2(B,v) levels which are in close energy resonance with N2(A or W) vibrational levels.