Electron scattering in cooled HCl: boomerang structures and outer-well resonances in elastic and vibrational excitation cross sections

Differential cross sections for elastic scattering and excitation of the v = 1 vibrational level have been measured for rotationally cooled HCl at energies near the threshold for dissociative attachment. The cooling improves the visibility of the oscillatory structure in the v = 0 → 1 cross section and permits the observation of a similar structure also in the elastic channel. The integral v = 0 → 1 cross section and the resonant part of the integral elastic cross section have been calculated using a nonlocal resonance model. A high degree of agreement of the details of the measured and calculated structures confirms the correctness of the model and the high accuracy of the ab initio HCl^- potential-energy function used as input to the model.