Research Papers in Physics and Astronomy


Date of this Version

January 1967


Published in Radiation Research 30, 855-871 (1967). Copyright © 1967 Radiation Research Society. Used by permission.


The response of dry enzymes and viruses to heavy ion bombardment may be predicted from their response to γ-irradiation (and no further knowledge of their size and structure). The molecules are approximated as point particles whose response to ionization is the same for heavy ion bombardment as for γ-rays. From the δ-ray distribution formula and an extrapolated range-energy relation for electrons, the radial distribution of secondary ionization energy may be found. Under this dosage distribution the inactivation probability may be found as a function of radial distance from the ion's path, and then may be integrated over all space to find the inactivation cross section. These essentially geometric theoretical relations between the γ-ray D37 values and the inactivation cross section constitute a complete theory of RBE for the heavy ion bombardment of these substances. Theoretical relationships agree with published experimental values to an average deviation of 15 % for the enzymes , β-galactosidase and trypsin, and for T-1 and φX-174 bacteriophages, when bombarded with ions ranging from Z = 1 to 18, at ion speeds of 0.07 c (2.3 MeV/nucleon) and 0.145 c (10 MeV/nucleon).

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