Radiation-induced D/H Exchange Rate Constants in Aliphatics Embedded in Water Ice

Gas-phase and solid-state chemistry in low-temperature interstellar clouds cores leads to a D/H enhancement ices, which is eventually inherited by comets, meteorites, even planetary satellites. Hence, the D/ H ratio has been widely used as tracer for origins of extraterrestrial chemistry. However, can also be influenced cosmic rays, are ubiquitous penetrate dense molecular cores. The effects such high-energy radiation on deuterium fractionation have not studied quantitative manner. In this study, we present rate constants radiation-induced D-to-H exchange fully deuterated small (1-2 C) hydrocarbons embedded H2O ice at 20 K H-to-D protiated forms these molecules D2O K. We observed larger versus ice, attributed greater bond strength C-D C-H. find that smaller methane than ethane, agreement with energies from literature. unable obtain unsaturated reactive ethylene acetylene. Interpretation suggest products formed abundance alongside radiolysis products. discuss how our qualitative data interpret ratios aliphatic compounds throughout space.