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Differential elastic electron scattering cross-sections of pyrimidine


Large part of the energy deposition by ionizing radiation in matter occurs in the form of the release of secondary electrons which cause - due to their mobility and the large number - considerable radiation damage in the lateral environment of the primary radiation track. For some time, increased efforts have been made worldwide to develop new Monte Carlo Codes with the aim of eliminating the weak points of the codes available so far in the calculation of the radiation damage - in particular by low-energy electrons. The accuracy of these calculations depends decisively on the electron scattering cross-sections of components of the critical target DNA implemented in the codes.

In view of this fact, differential elastic scattering cross-sections of pyrimidine, the basic component of the nucleic bases cytosine and thymine, were absolutely measured for electron energies from 20 eV to 1 keV and for scattering angles from 5° to 135°. In addition, they were calculated using Modified Independent Atom Models [1] for electron energies between 60 eV and 1 keV. As examples, Figures 1 a - c show the measured differential elastic scattering cross-sections of pyrimidine for electron energies of 100 eV, 300 eV and 1 keV, in comparison to the theoretical values and to the experimental data of Maljkovic et al. [2].

Figure : Differential elastic scattering cross-sections of pyrimidine for electrons with energies of 100 eV (a), 300 eV (b) and 1 keV (c): () present results of this paper, () experimental data of Maljković et al. [2], (-) theoretical values.

The figure shows that the agreement between the measured values and the theoretical values becomes better with increasing energy. This can be expected due to the approximation used in the theoretical model. In addition, the shoulder structure in the experimental data is well reproduced by the theoretical value in the scattering angle range around 35, which indicates that the structure is authentic. The present experimental results show large deviations compared to those of Maljković et al. [2] for the scattering angles above 60°. For electrons with a kinetic energy of 100 eV, the relative deviation in this scattering angle range amounts to approximately 80 %.


  1. S. Hayashi and K. Kuchitsu, J. Phys. Soc. Japan 41, 1724 (1976)
  2. J. B. Maljković, A. R. Milosavljević, F. Blanco, D. Šević, G. García and B. P. Marinković, Phys. Rev. A 79, 052706 (2009)