Electron transfer from electronic excited states to sub-vacuum electron traps in amorphous ice

We investigate the electron stimulated yield of electronically excited argo n atoms (Ar*) from monolayer quantities of Ar deposited onto thin films of amorphous ice. Two peaks of narrow width (<0.4 eV) are observed at incident electron energies of 11.6 and 10.7 eV, i.e., below the energy threshold fo r exciton creation in Ar. Both features stem from decay of the Ar- electron -exciton complex into exciton states, by the transfer of an electron into a sub-vacuum electron state within the ice film. However, the 10.7 eV featur e is shifted to lower energy since electron attachment to Ar occurs within small pores of amorphous ice. In this case, the excess electron is transfer red into an electron trap below the conduction band of the ice layer.