Diverse isotopes such as 2H, 3He, 10Be, 11C and 14C occur in nuclear reactions in ion beam radiotherapy, in cosmic ray shielding, or are intentionally accelerated in dating techniques. However, only a few studies have specifically addressed the biological effects of diverse isotopes and were limited to energies of several MeV/u. A database of simulations with the PARTRAC biophysical tool is presented for H, He, Li, Be, B and C isotopes at energies from 0.5 GeV/u down to stopping. The doses deposited to a cell nucleus and also the yields per unit dose of single- and double-strand breaks and their clusters induced in cellular DNA are predicted to vary among diverse isotopes of the same element at energies < 1 MeV/u, especially for isotopes of H and He. The results may affect the risk estimates for astronauts in deep space missions or the models of biological effectiveness of ion beams and indicate that radiation protection in 14C or 10Be dating techniques may be based on knowledge gathered with 12C or 9Be.

Department of Radiation Dosimetry Nuclear Physics Institute Czech Academy of Sciences Na Truhlářce 39 64 180 00 Prague Czech Republic

Institute of Radiation Medicine Helmholtz Zentrum München GmbH German Research Center for Environmental Health Ingolstädter Landstr 1 85764 Neuherberg Germany

Radiation Biophysics and Radiobiology Group Physics Department University of Pavia 27100 Pavia Italy

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