Quasifree electron bremsstrahlung induced by 20-MeV-proton impact

Energy spectra and angular distributions of quasifree electron bremsstrahlung (QFEB) induced by 20-MeV-proton bombardments of a Be target have been measured with a Si (Li) detector. The Doppler shift of QFEB is clearly observed in the energy spectra and depends on the observation angle. The production cross section calculated from a free-electron approximation is compared with the experimental result and the agreement is quite satisfactory. The spectral shape near the high-energy end point of the QFEB definitely reflects the velocity distribution of the orbital electrons of the target atom. Angular distributions of secondary-electron bremsstrahlung were also measured and are compared with a calculation which includes relativistic retardation effects.