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Total electron-scattering cross sections of pyrimidine

31.01.2011

Electron scattering cross sections of DNA constituents are important for the calculation of particle track structure. This is particularly the case for total electron-scattering cross sections that are used to check the consistency of experimental datasets of differential interaction cross sections and to bring the latter on an absolute scale when they were measured only relatively. Furthermore, total scattering cross sections are needed to determine the distance between two consecutive interaction points in Monte Carlo simulations of radiation transport.

After the experimental determination of the electron-scattering cross sections of the molecular groups of the DNA backbone, now also the total electron scattering cross sections of pyrimidine - the basic constituent of the nucleic bases cytosine and thymine - were measured. The measurement was performed using a linear transmission experiment for electron energies T between 20 eV and 1 keV. Figure 1 shows the measurement results compared to theoretical values [1] which were calculated using the independent-atom screening-corrected additivity rule. The two data sets show good agreement within the measurement uncertainties.

Figure 2 shows as a function of the electron energy T the total electron scattering cross sections of various organic molecules that have been normalised to the number Nval of valence electrons. It is evident that at electron energies of about 20 eV or higher, the total electron scattering cross sections are well scaleable with the number of valence electrons.

Figure 1 : Total electron-scattering cross sections σt of pyrimidine as a function of kinetic energy T obtained by experimental () compared to theoretical values calculated using the independent-atom screening-corrected additivity rule (-) [1].

Figure 2 : Total electron-scattering cross sections of various organic molecules, normalised to the number of valence electrons Nval

Literature

  1. A. Zecca, L. Chiari, G. Garcia, F. Blanco, E. Trainotti and M. J. Brunger, J. Phys. B: At. Mol. Opt. Phys. 43, 215204 (2010).