Inelastic mean free paths and stopping powers of light charged particles in dry DNA

The present study provides inelastic mean free paths (IMFPs) and stopping powers (SPs) of electrons and positrons in dry DNA. Full Penn-Lindhard model is adopted. It uses Linhard dielectric functions to evaluate the complete Bethe surface from contributions of electron hole and plasmon loss creation; The experimental optical data of Inagaki and the generalized oscillator strength (GOS) calculations are used together with sum rules to evaluate the full optical energy loss function (OELF) for zero momentum transfer. Acceptable agreement is achieved by comparing our finding to the literature for incident kinetic energies >100 eV. As a main new result, our electron IMFPs obtained from the full Penn-Lindhard-OELF agree very well (<1 %) with those calculated with the Mermin ELF-GOS in the energy range 100 eV-10 keV; in contrast to recent literature, no scaling factor is needed to compare the two models in dry DNA. The second new result is that the positron to electron IMFP and SP ratios differ from unity up to 1 keV. Data for electrons and positrons are scarce, so we provide tables of IMFP and SP in dry DNA from 10 eV to 50,000 eV.