In recent years, laboratory experiments and theoretical calculations have suggested that condensed-phase radiation chemistry plays a vital role in the synthesis of prebiotic molecules in a variety of extraterrestrial environments such as the ice of interstellar (sub)micron-size grains, extra-solar and solar planets (e.g., Mars), dwarf planets (e.g., Pluto), moons (e.g., Europa), asteroids (e.g., Ceres), and comets (e.g., 67P/Churyumov–Gerasimenko). The role of low-energy (&lt; 20 eV) secondary electrons, the agents of radiation chemistry, however, has not yet been extensively studied in the context of astrochemistry. The interactions of extraterrestrial ices with cosmic ray particles with energies up to 1020 eV produce ionization, triggering a cascade of secondary low-energy electrons and, consequently, radiation-induced chemical reactions. Fermi-type calculations have shown that low-energy secondary electrons have estimated fluxes of ~ 102 electrons cm−2 s−1 within interstellar dust grains. This order-of-magnitude calculation involves many assumptions, including an average value for the energy required to produce electrons. In contrast, Geant4-DNA, an open-source, Monte Carlo simulation toolkit capable of modeling particles’ interactions with matter, allows users to examine the energy deposited by ionizing radiation more accurately. This program is employed to (1) simulate cosmic ray irradiation of the cosmic ices and (2) discern the number (as a function of electron energy) and location of secondary electrons produced within the ice. This second goal will allow for quantifying the role, if any, of secondary electrons in the initial genesis of life.

Monte Carlo simulations of low-energy (< 20 eV) electrons in astrochemistry

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.