Rotational pathways in electronic energy transfer

We analyze rotational distributions from collision-induced atom-diatom electronic energy transfer (EET) experiments in terms of the capacity of the diatomic to dispose of the angular momentum (AM) generated in state-to-state change. Two pairs of systems are chosen as representative of processes broadly categorized as efficient or inefficient in this regard, namely, Na-2-Na, Li-2-Li in the former category and N-2(+)-He, CN-Ar in the latter. Note that EET involving electron spin change is not considered here. Using velocity-AM diagrams and quantitative calculations we show the factors that govern the probability of state-to-state transfer in EET are the same as those controlling the outcome of rotational and rovibrational transfer within an electronic state. This suggests that requirements of orbital and rotational AM are of critical importance in providing pathways that allow EET to proceed. (C) 2001 American Institute of Physics.