Absolute cross sections for electronic excitation of condensed tetrahydrofuran (THF) by 11-16 eV electrons

Abstract

Absolute cross section (CS) data on the interaction of low energy electrons with DNA and its molecular constituents are required as input parameters in Monte-Carlo type simulations, for several radiobiological applications. Previously [V. Lemelin et al., J. Chem. Phys. 144, 074701 (2016)], we measured absolute vibrational CSs for low-energy electron scattering from condensed tetrahydrofuran, a convenient surrogate for the deoxyribose. Here we report absolute electronic CSs for energy losses of between 6 and 11.5 eV, by electrons with energies between 11 and 16 eV. The variation of these CSs with incident electron energy shows no evidence of transient anion states, consistent with theoretical and other experimental results, indicating that initial electron capture leading to DNA strand breaks occurs primarily on DNA bases or the phosphate group.

Excitation and ionisation cross-sections in condensed-phase biomaterials by electrons down to very low energy: application to liquid water and genetic building blocks

“…The differences with respect to the BEB calculations and other experiments can in principle be attributed to phase effects. As for the TECS, full calculated results (solid line) are compared to the experimental data for the condensed phase [24] and for the gas phase [14,17], as well as the recommended data by [77]. Data from [24] are too low in comparison with our calculations, being the agreement rather good with [14,17,77].…”

“…As for the TECS, full calculated results (solid line) are compared to the experimental data for the condensed phase [24] and for the gas phase [14,17], as well as the recommended data by [77]. Data from [24] are too low in comparison with our calculations, being the agreement rather good with [14,17,77]. Although our calculations for energies below 30 eV are quite smaller than the data compiled in [17], it should be noted that the latter also includes, apart from electronic excitations, vibrational and rotational excitations, which we did not considered in our treatment.…”

“…Solid lines correspond to our full calculations for TICS and TECS, while the dotted line in (a) corresponds to the sum of both. Other lines and symbols represent experimental data: for THF, gas-phase TICS [14,15,17,18,74] and TECS [14,17,77], solid-phase TECS (for T < 11.5 eV) [24], and gas-phase total electronic cross-section [78]; for cytosine, gas-phase TICS [16,23,79,80] and solid phase TECS [23]. BEB calculations for THF [29] and cytosine [28] are depicted by dash-dotted lines.…”

“…7(d)). For these materials, measurements are available for the condensed phases from electron energy loss spectroscopy [23,24]. These data are very relevant, since they are among the few available for the electron cross-sections determination in solid biomaterials.…”

“…Plenty of experimental information is available on electron-impact ionisation cross-sections (total probabilities as well as energy spectra of ejected electrons) of relevant biomolecules (such as water or DNA nucleobases), * pablo.vera@um.es however it is usually limited to the gas phase [12][13][14][15][16][17][18], without taking into account the condensed phase nature of living organisms. Experimental data on electronic excitations are much scarcer and scattered [17,[19][20][21][22] and also limited just to molecules in the gas phase, with only a few exceptions [23,24]. An alternative for gathering all relevant cross-sections resorts into theoretical calculations, where some very successful ab initio approaches are available for calculating both excitation and ionisation cross-sections [25,26].…”