Rydberg molecules in external fields: A semiclassical analysis - art. no. 143002

We analyze the spectra of simple Rydberg molecules in static fields within the framework of closed/periodic-orbit theories. We conclude that in additi on to the usual classical orbits one must consider classically forbidden di ffractive paths. Further, the molecule brings in a new type of "inelastic" diffractive trajectory in addition to the usual "elastic" diffractive orbit s encountered in systems with point scatterers. The relative importance of inelastic versus elastic diffraction is quantified by merging the usual clo sed orbit theory framework with molecular quantum defect theory.