Electron-stimulated desorption of D2O coadsorbed with CO2 ice at VUV and EUV energies

Abstract

Electron-induced processes in water ice and CO2 ice are important in planetary science. We have measured desorption yields of positive ion products (C+, O+, D+, D3O+, CO+, O2+) produced as a result of exposing pure CO2 and D2O adsorbed on CO2 ices to 10–100 eV (i.e., the vacuum-ultraviolet–extreme-ultraviolet energy region) electron beams. Measurements on pure CO2 ice irradiated with 40-eV electrons suggest that pores in the CO2 ice are responsible for trapping molecular precursors for bimolecular reactions that are responsible for O2+ production. Investigations of pure CO2 ice irradiated with a 100-eV electron beam reveals production of O2+ by a second channel attributed to post-ion molecule collisions that are strongly influenced by low-energy electrons trapped in the ice. The most significant finding is that the D+ and D3O+ yields as a function of both dose and time indicate that the D2O adsorbed on CO2 at 30 K diffuses into the CO2 ice or desorbs into vacuum very rapidly. Both processes are a result of electron irradiation.

Reactions and luminescence in passivated Si nanocrystallites induced by vacuum ultraviolet and soft-x-ray photons

“…33 Our attribution of the higher binding-energy peak in spectra from the slow samples to photoinduced oxidation is supported by results of recent VUV surface photochemical studies of water adsorbed on graphite 35 and CO 2 ice. 36 It was shown that H + ͑D + ͒ and H 3 O + ͑D 3 O + ͒ ion fragments can readily desorb into vacuum, leaving OH species ͑possibly in an excited state͒ trapped at the surface and thus available for silicon oxidation. Desorption of hydrogen from Si surfaces can also be induced under VUV photoirradiation 37,38 and the resultant dangling bonds would be able to act as reaction sites.…”

Space-Weathering of Solar System Bodies: A Laboratory Perspective

“…The total desorption yield (molecules/photon) was assessed to be 1.4% at 6 K and 20% at 50–60 K. Direct CO 2 emission from this PSD process was found to be significantly lower than that from Öberg et al, but the studies determined that the CO 2 desorption yield was temperature-, fluence-, and thickness-dependent. Electron irradiation studies of CO 2 ice measured desorption yields of a variety of positive ion products such as C + , O + , D + , D 3 O + , CO + , O 2 + . The authors showed that the production channel of O 2 + was energy-dependent.…”

Electron-induced chemistry of methyl chloride caged within amorphous solid water

“…[1][2][3][4][5][6][7] In model laboratory studies electrons may originate indirectly from photo-induced processes 8 or from a well defined electron gun source. [9][10][11][12] The motivation for such studies arises from the need to better understand the physics and chemistry at the outer space 13 as well as phenomena occurring at the stratosphere, 14 where solid particles are covered by layers of ice. 15 The interaction of electrons with molecules adsorbed on metal or oxide substrates is often described by the Menzel-Gomer-Redhead (MGR) 16,17 model.…”