Secondary ion emission from C2H6:H2O ice by fission fragments

Abstract

Water (H2O) ice is a common constituent of several astrophysical object surfaces; other condensed gases (e.g., CH4, CO2, NH3, and C2H6) also occur in specific bodies. Bombarded by cosmic rays, these molecules react among them, generating new molecular species, which are partially ejected to the gas phase via a process called sputtering. In the current work, C2H6:H2O ice is irradiated at an averaged temperature of 100 K by energetic multicharged ions (252Cf fission fragments of ∼ 65 MeV). The sputtered positive and negative secondary ions are detected and analyzed by time-of-flight mass spectrometry (PDMS-TOF). The projectile-surface collision induces the formation of ionic cluster series (H2O)nX (X = H2O+, H3O+, O− and OH−), and their yield distribution can be represented by the sum of two decreasing exponentials, suggesting the presence of a two distinct formation processes, one for the low cluster masses and another for the larger ones.