Nuclear-reaction recoil fragments as probes of electronic structure in condensed matter

Ambiguities in the stopping powers of many solids are frequently observed. When the cross-sections for constituent atoms are reliable, the deviations can be discussed meaningfully. This work measures cross-sections for boron, hexagonal boron-nitride, cubic boron-nitride (borazon) and cubic boron-phosphide and suggests that these samples may provide reasonable atomic cross-sections. Intermolecular deviations may exist, but molecular deviations appear to be absent. The method used for measuring cross-sections is based on information obtained from radiating Li7 projectiles, whose motion and internal excitation are initiated by the thermal nuclear reaction 10B(n,α)7Li*. These projectiles have well defined initial momentum and spend their entire lives confined to the stopping medium