Dispersion corrections to the forward Rayleigh scattering amplitudes around the L‐shell of tantalum and lead

Abstract

Dispersion corrections to the forward Rayleigh scattering amplitudes of tantalum and lead in the photon energy range 6.4–24.14 keV were determined by a numerical evaluation of the dispersion integral that relates them through the optical theorem to the photoelectric cross‐sections. The photoelectric cross‐sections were extracted by subtracting the coherent and incoherent scattering contribution from the measured total attenuation cross‐section, using a high‐resolution, high‐purity germanium detector in a narrow‐beam good geometry setup. The real part of the dispersion correction to which the relativistic corrections calculated by Kissel and Pratt (S‐matrix approach) or Creagh and McAuley (multipole corrections) have been included are in better agreement with the available theoretical values than those values to which the relativistic corrections calculated by Cromer and Liberman (dipole corrections) are added. Copyright © 2006 John Wiley & Sons, Ltd.

Determination of the anomalous scattering factors of high-Zatoms using bremsstrahlung radiation

“…Many researchers have determined experimentally the anomalous scattering factors at various photon energies [15][16][17][18][19][20][21][22][23]. Normally, two methods are adopted to determine f and f values, namely the direct method and the indirect method.…”

“…The indirect method is the attenuation method. In this method, the form factors are determined using either monoenergetic gamma sources or the synchrotron radiation [17][18][19][20][21][22][23]. Dreier et al [17] determined the anomalous x-ray scattering factors of Ni, Cu, Zn and Zr close to K absorption edges and of Ta, W, Pt and Au close to L edges by applying the dispersion relation to the absorption spectra.…”

Determination of the K shell oscillator strengths and the imaginary form factors of atoms using a weak beta source

“…Similarly, several investigators have experimentally determined atomic form factors for various elements at various energies [25][26][27][28][29][30][31][32][33][34][35][36]. Normally, two methods are adopted for measuring the form factors, namely the direct method and the attenuation method.…”

“…The direct method is based on (a) measurement of reflection and refraction [25,26], (b) determination of the intensities of the Bragg reflected rays [27,28] and (c) x-ray interferometry [29,30]. However, the measurement of atomic form factors using the attenuation method is more reliable [31][32][33][34][35][36] and does not suffer from the problems associated with the other methods. The other advantage of the attenuation method is that the atomic form factors can be determined for a larger range of atomic numbers over a wider range of x-ray or gamma-ray energies.…”

“…Here, they have used monoenergetic gamma sources for measuring the attenuation co-efficient. Recently, Appaji Gowda and Umesh [35,36] have determined the atomic form factors of tantalum, mercury and lead using the gamma-ray attenuation method. Recently, de Jonge et al [5] have measured the atomic form factor of tin over the energy range of 20-60 keV using synchrotron radiation.…”