Monte Carlo-simulated Auger electron spectra for nuclides of radiobiological and medical interest – a validation with noble gas ionization data

Purpose: To further validate Monte Carlo calculation codes simulating cascades of Auger electron transitions in radionuclides that decay by electron capture or internal conversion. In particular, the need for an appropriate kinetic energy determination of the Auger electrons emitted from multiple-ionized atoms as well as the consideration of shake-off electrons would be investigated implicitly. Methods: Charge distributions of noble gases after photoionization for different photon energies were calculated and compared with experimental data from the literature. In addition, new electron emission spectra were generated for ^99mTc and ¹²³I. Results: By including strict energy book-keeping and allowing shake-off electrons, the agreement between experimentally detected charge distributions and Monte Carlo simulations was very good. On this basis, the number of emitted electrons per decay was found to be between 1 and 17 with a mean of 4.0 for ^99mTc and between 1 and 26 with a mean of 7.4 for ¹²³I. Conclusions: Because of the good agreement with the experimental findings, the validation can be considered to be successful. (authors)