NCNO → CN+NO: Complete NO(E, V, R) and CN(V, R) nascent population distributions from well-characterized monoenergetic unimolecular reactions

Abstract

We report detailed vibrational, rotational, and electronic (V, R, E) distributions of nascent NO(X 2Π) deriving from monoenergetic unimolecular reactions of jet-cooled NCNO. Excitation is via the à 1A″ ← X̃ 1A′ system above dissociation threshold (17 085±5 cm−1), and vibrational predissociation occurs following radiationless decay of the initially excited à 1A″ state. These results are combined with data on the corresponding CN(X 2Σ+) nascent V, R distributions, thereby providing a complete description of the energy partitioning into the various degrees of freedom of both products. The data presented here support our previous conclusion that dissociation is ‘‘statistical.’’ All the V, R distributions of both products can be predicted accurately using a modification of the phase space theory of unimolecular reactions (PST), which we call the separate statistical ensembles (SSE) method; it is expected that this method will have quite general applicability. NO spin-orbit excitation is ‘‘cold’’ relative to the V, R degrees of freedom, and although no detailed explanation is offered, the origin of this observation is discussed.