Radiolysis may play an important role in the chemical transformation of astrophysical or planetary surface ices. It is well established that secondary electrons with energies less than 100 eV are among the most numerous species created in matter by ionizing radiation (e.g., cosmic ray, X-rays, and UV). In this work, we examine the hypothesis that low energy electrons with energies less than 100 eV are responsible for the formation of molecular components in planetary or astrophysical surface ices. To this end, we have employed electron stimulated desorption (ESD), X-ray photoelectron spectroscopy (XPS) and temperature programed (TPD) mass spectrometry to study the chemical species generated from multilayer N2O/C2D2 samples by the impact of low energy electrons (30- 70 eV). Our ESD results indicate multiple large, molecular cations desorbed from the mixture of N2O/C2D2 with sufficient kinetic energy to escape into vacuum. The ESD signals of anions further suggest the slow accumulation of C-N and C-O containing species within the irradiated films. XPS spectra of N1S, C1S and O1S lines reveal the fragmentation of N-O and gradual formation of molecules containing COOH and/or O=C=O functional groups. Comparison between ESD and XPS finding show that species  observed in the ESD channel are primarily products of reactions taking place at the film vacuum interface, while those observed  XPS derive from reactions occuring within the solid. Further, our TPD measurements to candidate radiation products will be presented and discussed.

New chemical species produced by low energy electrons in simple molecular surface ices containing N2O and C2D2: Chemical transformation of surface ices

248th National Meeting (2014)

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