On the key factors of angular correlations in complex-forming elementary reactions

In the mid-seventies, Case and Herschbach argued that for complex-forming three-atom reactions governed by long-range forces and performed in supersonic molecular beam experiments, vectorial properties are determined by a single parameter Lambda' = < L'/(L'+j')>, L' and j' being respectively the moduli of the orbital and rotational angular momenta of the products. A simple mathematical relation between vectorial properties and Lambda' was then proposed. However, Lambda' must be determined beforehand by phase space theory calculations. Besides, we have recently shown that scalar properties are mainly controled by two factors. rho(')(1) and rho(')(2) respectively called angular excitation and diatomic inertial contribution. We show here that these factors control also vectorial properties. Moreover, the way they control them is summarized in a set of four figures. The advantage of our method is that rho(')(1) and rho(')(2) are related to the mechanical parameters of the reaction by very simple formulas, contrary to Lambda'. Last by not least, our parameters appear to be mostly independent, so that vectorial properties cannot be said to strictly depend on Lambda'. Nevertheless, it turns out that the rule proposed by Case and Herschbach is reasonable in many realistic situations.