Angular momentum disposal in atom exchange reactions

Abstract

For an A + BC → AB + C reaction, the partitioning of the total angular momentum J between initial and final orbital momenta of the collision partners, l and l′, and rotation of the reactant and product molecules, j and j′, often imposes distinctive dynamical features. Many examples are known that approach one or another of two very different limiting cases: (I)J=l=j′ or (II)J=l=l′. In a quasiclassical trajectory study of the H + Li₂→ LiH + Li reaction, we find the distributions of the product scattering angle and the rotational orientation of j′ relative to the initial velocity conform to case II. However, the dihedral orientation of j′ relative to the plane of initial and final velocity vectors conforms to case I. Also, the opacity function has an unusual bimodal form and the entropy deficiency for the triple-angle correlation is extremely large. The culprit is vector addition: both j′ and l′ are large and largely opposed, so the reaction appears schizophrenic.