Gateway coupling between quartet and doublet states of 15N18O studied in molecular beams

Collision-induced intramolecular electronic energy transfer in NO was studied using a beam of metastable 15N18O(a 4Π) molecules colliding with Ar atoms in a cell. As in our earlier work on 14N16O and 15N16O, selective excitation of certain NO(B 2Π) levels was observed by means of their β-band emission. In the B, ν = 2 level three emitting levels could be uniquely identified in terms of rotational, fine structure and Λ component quantum numbers. They are gateway-coupled to likewise fully characterized b-state levels, which are collisionally populated from the a state. Weaker and less specific emission from the B, ν = 3 level was also observed, but not rotationally assigned.