Auger Electron Spectra - The Basic Data for Understanding the Auger Effect

Abstract

Understanding the strong radiotoxicity of DNA-incorporated Auger electron-emitting nuclides requires a detailed knowledge of the nuclide's emission spectrum. A Monte Carlo computer code was previously developed to simulate Auger cascades and to provide electron spectra of 125I. To utilize experimental data for a direct validation of these simulations, the code has been adapted for cascades in xenon, which is adjacent to iodine in the table of elements. Only minor modifications of the code were necessary to obtain a very good agreement with the experimental findings. The role of shake-off electrons and the need for energy considerations during the cascades could be demonstrated. A previously published electron spectrum of 125I was recalculated and detailed results are presented here. Furthermore, to consider implications from a molecular binding of the Auger emitter, for the first time semi-empirical quantum mechanical calculations for an iodine-labelled thymine molecule were performed showing that even in the condensed phase a Coulomb explosion cannot be excluded a priori.

A Model to Realize the Potential of Auger Electrons for Radiotherapy

“…In accord with our assumption that valence-shell vacancies persist, our results are consistent with those of Pomplun [19,20]. We have therefore demonstrated that we can reproduce the previous Monte Carlo calculations for these isotopes.…”

Fast He2+ion irradiation of DNA loaded with platinum-containing molecules

“…The spectrum of emitted Auger electrons -the number of electrons and energy released as a function of the targeted inner shell -is given in the Appendix (Pomplun 2000, M. Terrissol, personal communication, 2005. For comparison, in 125 I the total number of electrons emitted per decay is on the average, 21.2 and the total electron energy is 19.8 keV (see Charlton & Booz 1981).…”

Auger yield calculations for medical radioisotopes

“…Their approach could lead to wrong estimation of absorbed doses in dosimetry and microdosimetry using medical radioisotopes. The approach adopted by Stepanek et al [9,10] and Pomplun [13,14] is closer to the one adopted in our work as these authors calculate transition energies quantum mechanically. In contrast, Eckerman and Endo [12], Howell [8], and Nikjoo [15] used the Z/Z+1 rule [44] to estimate transition energies.…”

“…Experimental data on Auger emitters is scarce but calculated Auger yields of these common Auger emitters have been published by various authors [8][9][10][11][12][13][14][15]. However, there is a large scatter in the literature data for these common radioisotopes, and available data for exotic Auger emitters is meagre.…”