Electronic Excitation Transport in Ices: A Key Role for Hydrogen Bonding

We have previously reported observations of large (>10^-16 cm2), low-energy (<500 eV), electron-promoted desorption cross-sections for benzene (C6H6) molecules adsorbed on the surface of amorphous solid water [1]. We will now report on the extension of this work to other molecular solids exhibiting varying degrees of hydrogen bonding within the molecular solid itself and between the solid surface and adsorbed benzene; specifically we have repeated our measurements employing substrates comprised of solid methanol (CH3OH) and diethyl ether (CH3CH2OCH2CH3). Our report will detail our studies of the structure of adsorbed layers of C6H6 on the molecular solids and demonstrate the crucial role of hydrogen bonding in propagating electronic excitation to the solid-vacuum interface where C6H6 desorption can occur. Competitive electron-promoted chemistry in the form of H2 formation will also be reported. Conclusions related to the impact of these observations on the early phase of icy interstellar grain chemistry will be discussed. [1] Highly efficient electron-stimulated desorption of benzene from amorphous solid water ice, J. D. Thrower, M. P. Collings, F. J. M. Rutten, and M. R. S. McCoustra, Chem. Phys. Lett., 2011, 505, 106–111.