Fine-structure electronic predissociation in van der Waals molecules. I. Theory

A quantum-mechanical model for fine-structure predissociation in van der Waals molecules is presented. The process corresponds to: A(2S+1LJA )⋅⋅⋅M→A(2S+1LJ′A) +M where A is an atom and M an atom or a diatomic molecule A(2S+1LJA) ⋅⋅⋅M represents the van der Waals complex in a state which correlates to the 2S+1LJA electronic manifold of A. The general formalism based on close-coupling equations is presented first. The limiting case of slow predissociation is then considered and treated by perturbation theory. Finally, the application to the atom–atom and the atom–diatom van der Waals complexes for L=1 and S=1/2 or S=1 is discussed. This simple analysis allows predictions to be made for predissociation rates and lifetimes in cases where the spin–orbit interaction is larger than the van der Waals binding energy.