Interband excitation of single alkali-halide nanocrystals in the form of mass-selected Mn1Xn beams (M=K, Cs and X=Br I) by ultraviolet radiation leads exclusively to halogen-atom emission with very large cross section. The final state is a midgap (F-center) state. A pathway consisting of direct ejection of a photoneutralized surface atom is derived from a band picture using the computed energetics of the (3,3,3) nanocrystal M14X13+. This mechanism is contrasted with photon-stimulated desorption from crystal surfaces, and related to formation of surface defect states and metallized overlayers.
ASJC Scopus subject areas
- Physics and Astronomy(all)