Weber, M. H.Hunt, A. W.Golovchenko, JeneLynn, K. G.2016-11-171999Weber, M. H., A. W. Hunt, J. A. Golovchenko, and K. G. Lynn. 1999. Energy-Resolved Positron Annihilation in Flight in Solid Targets. Physical Review Letters 83, no. 22: 4658–4661. doi:10.1103/physrevlett.83.4658.0031-9007http://nrs.harvard.edu/urn-3:HUL.InstRepos:29405825Energy-resolved two-quantum annihilation in flight of positrons with energies ranging from 10 to 71.6 keV was observed. An energy-dispersive two-detector coincidence system was used to observe the sum and difference energies of the γ rays from annihilating positron-electron pairs. For positrons penetrating carbon foils the c/v dependence of the annihilation cross section is confirmed. Spectra obtained from gold-coated carbon foils show evidence of in-flight annihilation with gold M−shell electrons.en-USJournal Article2016-11-1710.1103/PhysRevLett.83.4658