We have measured cross sections for the ionization of the K shell by electrons with energies from the respective thresholds up to 100 keV, for Au and Bi. The experimental values are obtained by dividing the number of counts in the Kα peak by the number of counts in an energy interval near the tip of the bremsstrahlung continuum, and multiplying this ratio by the theoretical estimate of bremsstrahlung emission towards the detector in this energy interval. Although such a procedure has already been described in the literature, here it is implemented avoiding some of the simplifications made in earlier works. Our experimental cross sections, which are the first ones to be reported for atoms with > Z 47 close to the threshold, are in reasonable agreement with the theoretical predictions of the semirelativistic distorted-wave Born approximation. Hipplerʼs plane-wave Born approximation with corrections for Coulomb and exchange effects yields cross sections that are closer to the experimental data than those evaluated from the relativistic binary-encounter-Bethe model.

We have measured the Lα, Lβ, , , L , and Lη x-ray production cross sections of Au by 50–100 keV electron impact. From this experimental information we derived the L1, L2 and L3 subshell ionization cross sections with a novel analysis procedure that is based on an overdetermined system of equations and achieve the estimates by the least-squares method. The uncertainties in the atomic relaxation parameters needed to transform the x-ray intensities to ionization cross sections impose a lower limit to the relative standard deviations of the L subshell ionization cross sections, which is found to be 5–10% depending on the selected set of relaxation parameters. Our experimental results are in reasonable accord with most of the measurements carried out by other authors, and they agree with the predictions of the semi-relativistic distorted-wave Born approximation.

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We have used the low-energy beam line of the São Paulo Microtron accelerator to study the maximum energy transfer point (tip) of electron-atom bremsstrahlung spectra for C, Al, Te, Ta and Au. Absolute cross sections differential in energy and angle of the emitted photon were measured for various electron kinetic energies between 20 and 100 keV, and photon emission angles of 35 • , 90 • and 131 • . The bremsstrahlung spectra were collected with three HPGe detectors and their response functions were evaluated analytically. Rutherford backscattering spectrometry allowed us to obtain the thicknesses of the targets with good accuracy. We propose a simple model for the tip region of the bremsstrahlung spectrum emitted at a given angle, whose adjustable parameters are the mean energy of the incident beam and its spread as well as an amplitude. The model was fitted simultaneously to the pulse-height distributions recorded at the three angles, determining the doubly differential cross sections from the corresponding amplitudes. The measured values have uncertainties between 3% and 13%. The agreement of the experimental results with the theoretical partial-wave calculations of Pratt and co-workers depends on the analyzed element and angle but is generally satisfactory. In the case of Al and Au, the uncertainty attributed to the theory is probably overestimated.

We report absolute measurements of doubly differential electron-atom bremsstrahlung cross sections for energies in the keV region and elements with atomic numbers 6, 13, 52, 73 and 79. Thin targets were irradiated at the low-energy beam line of the São Paulo Microtron with 20, 50, 75 and 100keV electrons. For each element and energy, the photon spectra were collected simultaneously with three HPGe detectors at the emission angles of 35°, 90°and 131°. The deconvolution of the bremsstrahlung spectra was done adopting an analytical model for the spectrometers' response functions. The resulting doubly differential cross sections are compared with the available partial-wave calculations of ordinary bremsstrahlung. Based on this comparison, we discuss some features of the experimental spectra that might be related to the emission of polarization bremsstrahlung.

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