Electron-Stimulated Desorption of Positive Ions from Methanol Adsorbed on a Solid Ar Substrate

Abstract

Electron-stimulated desorption (ESD) of positive ions from weakly physisorbed molecules has been investigated. From methanol adsorbed on a solid Ar substrate, the protonated cluster ions of the type H+(CH3OH) n(n = 1 - 4) are emitted, together with the fragment ions such as [Formula: see text](n = 0 - 3), H3O+, CHO+, CH3O+, etc. The yields of these ions are markedly enhanced at the smallest coverage and decay steeply with increasing coverage. Coulomb explosion between valence holes confined in adsorbed nanoclusters is responsible for the enhanced ion yields. Very few ions except for H+ are emitted from a thick layer as well as nanoclusters adsorbed directly on a metal substrate due to the delocalization of valence holes.

Non-thermal ion desorption from an acetonitrile (CH3CN) astrophysical ice analogue studied by electron stimulated ion desorption

“…The most intense desorbed fragment is the H + ion, what is consistent with the formation of a thick molecular film. 43 Also, light fragments, such as H + and H 2 + , have high initial kinetic energy, what lowers their residence time on surface, lessening their probability of neutralization. 44 In addition to H + and H 2 + , the H 3 + ion was also produced as a member of the H n=1-3 + ion series.…”

Desorption from Methanol and Ethanol Ices by High Energy Electrons: Relevance to Astrochemical Models

“…The H 3 O + fragment is seen in both spectra of Figure . It is well-known , that water can be produced from alcohol dissociation on the ice phase. Some water cluster series like (H 2 O) n (H 3 O) + were identified in the desorption spectrum of ethanol at energies higher than 1400 eV, as shown in Table .…”

“…Such an effect reduces the Coulombic repulsion between the valence holes and lowers the probability of heavy fragments desorption. Kawanowa et al also mention that the proton transfer to the methanol molecule occurs during molecular collisions in the condensed phase. In fact, previous gas phase studies ,, showed no evidence of protonated molecular cluster formation.…”

“…L. Sanche and co-workers studied H – desorption of condensed methanol films by low energy electron impact (0–20 eV). Kawanowa and co-workers analyzed with TOF-MS fragments desorbed from 1.5 keV electron impact on methanol ices weakly physisorbed on a solid Ar substrate. Bennett et al analyzed quantitatively by Fourier transform infrared spectroscopy (FTIR) fragment ions produced by 5 keV electron impact on pure ices of amorphous methanol, identifying new species with the aid of high-level electronic structure calculations.…”

Fragmentation and Ion Desorption from Condensed Pyrimidine by Electron Impact: Implications for Cometary and Interstellar Heterocyclic Chemistry

“…It is noteworthy that the same comparison is valid for previous gas-phase experiments, with either photons − or electron impact. ,, The reason for this is the influence of C–H···N intermolecular forces on the pyrimidine ice during fragmentation, which allows a number of rearrangements before desorption occurs. The role of intermolecular forces during ESID has been previously studied for condensed hydrogen-bonded molecules, − suggesting that strong ion–dipole interactions may favor proton-transfer reactions, rather than simple molecular dissociation.…”