Cross sections for iT-shell ionization have been measured at electron bombarding energies of 0.10, 0.15, 0.20, 0.25, 0.30, and 1.00 MeV for Ag, and of 0.20, 0.60, 0.80, 1.00, 1.20, 1.40, 1.70, and 2.00 MeV for Sn and Au. Below 0.50 MeV, the results for Ag are in excellent agreement with the relativistic calculations of Arthurs and Moiseiwitsch. For Sn at 0.20 and 0.60 MeV, where the theoretical values are available, the experimental cross sections are also in very close agreement. Although the experimental cross section for Au at 0.20 MeV is very nearly the same as the calculated result of Arthurs and Moiseiwitsch at this energy, at 0.60 MeV and higher electron energies the experimental results for Au are, on the average, about 15% lower than the values of Arthurs and Moiseiwitsch.

The bremsstrahlung produced by electrons with incident energies of 0.5, 1.0, 20., and 2.8 MeV bombarding aluminum and iron targets of sufficient thickness to stop the electrons, has been measured. Spectral distributions of external bremsstrahlung intensity per unit solid angle, at representative emission angles ranging from 0 to 150 deg are presented graphically. Spectral distributions of radiation energy integrated over all angles and integrated over only the forward hemisphere are presented. Plots of total intensity as a function of angle show the degree of peaking in the forward direction with increasing electron energy. Total external radiation energy is found to vary as the square of the bombarding electron energy T0 over this energy range. The external efficiency for bremsstrahlung production is found to be 4.8×10−3 T0 for Al and 9.2×10−3 T0 for Fe, where T0 is in MeV.

Electron bremsstrahlung due to bombardment of Sn and Au targets at 0.2, 1.0, 2.0, and 2.8 MeV, Be targets at 0.2, 1.0, and 2.0 MeV, and Al and Fe targets at 0.2 MeV were measured. Angular distributions of bremsstrahlung intensity and total transmission spectra are derived from the measurements, which were carried out for perpendicular incidence of the electron beam to the target plane. Comparisons for Au and for previously reported Al and Fe spectra are made at 1.0 and 2.8 MeV to calculated spectra from the Monte Carlo program of M. J. Berger and S. M. Seltzer, ETRAN 15. Total external radiation emitted from the targets is represented by the function 1.4×10−3 T02.16 for Be, 1.6×10−2 T02.07 for Sn, and 2.3×10−2 T01.90 for Au, where T0 is the incident electron kinetic energy in MeV.

Measurements of electron-bremsstrahlung cross sections have been made for incident electron energies of 1.0, 1.7, and 2.5 MeV and targets of Al, Cu, Sn,and Au. Data are included at angles of observation from 0° to a limiting angle including more than 90% of the total emitted bremsstrahlung at each incident electron energy. The present measurements are lower than the results of Motz for Al and Au at 1.0 MeV; however, the present results at 2.5 MeV agree with the results of Starfelt and Koch at 2.72 MeV. Comparison with the Born approximation indicates that the experimental cross sections are larger than predicted near the highfrequency limit. This effect increases with atomic number at a given energy but decreases with energy, as expected.

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