arXiv subjects

S. Eden

Publications and source records attributed to S. Eden.

3 recordsLinked to original sources

arXiv2009

Production of intense beams of mass-selected water cluster ions and theoretical study of atom-water interactions

The influences of water molecules surrounding biological molecules during irradiation with heavy particles (atoms,ions) are currently a major subject in radiation science on a molecular level. In order to elucidate the underlying complex reaction mechanisms we have initiated a joint experimental and theoretical investigation with the aim to make direct comparisons between experimental and theoretical results. As a first step, studies of collisions of a water molecule with a neutral projectile (C atom) at high velocities (> 0.1 a.u.), and with a charged projectile (proton) at low velocities (< 0.1 a.u.) have been studied within the microscopic framework. In particular, time-dependent density functional theory (TDDFT) was applied to the valence electrons and coupled non-adiabatically to Molecular dynamics (MD) for ionic cores. Complementary experimental developments have been carried out to study projectile interactions with accelerated (< 10 keV) and mass-selected cluster ions. The first size distributions of protonated water cluster ions H+(H_2O)_n (n=2-39) produced using this new apparatus are presented.

physics.atm-clus↗

arXiv2006

Electron-loss and target ionization cross sections for water vapor by 20-150 keV neutral atomic hydrogen impact

A complete set of cross sections is reported for the ionization of water molecules by neutral atomic hydrogen impact at velocities of the order of the Bragg peak. The measured relative cross sections are normalized by comparison with proton impact results for the same target conditions and previous absolute data. Event by event coincidence analysis of the product ions and the projectile enables partial cross sections for target ionization and target plus projectile ionization to be determined, as well as total cross sections for electron loss reactions.

physics.atm-clus↗

arXiv2006

Absolute cross sections for the dissociation of hydrogen cluster ions in high-energy collisions with helium atoms

Absolute dissociation cross sections are reported for Hn+ clusters of varied mass (n = 3, 5, ..., 35) following collisions with He atoms at 60 keV / amu. Initial results have been published in a previous brief report for a smaller range of cluster sizes [Ouaskit et al., Phys. Rev. A 49, 1484 (1994)]. The present extended study includes further experimental results, reducing the statistical errors associated with the absolute cross sections. The previously suggested quasi-linear dependence of the Hn+ dissociation cross sections upon n is developed with reference to expected series of geometrical shells of H2 molecules surrounding an H3+ core. Recent calculations identify n = 9 as corresponding to the first closed H2 shell [e.g. Stich et al., J. Chem. Phys. 107, 9482 (1997)]. Recurrence of the distinct characteristics observed in the dissociation cross section dependence upon cluster size around n = 9 provides the basis for the presently proposed subsequent closed shells at n = 15, 21, 27, and 33, in agreement with the calculations of Nagashima et al. [J. Phys. Chem. 96, 4294 (1992)].

physics.atm-clus↗