Low-energy Multiply Charged Ions Research Articles

Charge and energy flows in ionised thymidine

SynopsisWe present a combined experimental and theoretical study of the ionisation and fragmentation of the nucleoside thymidine in the gas phase. Two sources of ionisation/excitation are used, namely UV photons and low-energy multiply charged ions, associated with coincidences measurements, respectively photoelec- tron/photofragment (PEPICO) and fragment/fragment. Coupling these experiments with quantum chemistry calculations, we obtain a complete picture of the fragmentation dynamics, in particular the charge and energy transfers within the molecular edifice.

Stability of the glycine cation in the gas phase after interaction with multiply charged ions

This study presents a coupled experimental and theoretical work on the stability of singly charged glycine molecules (NH2CH2COOH+, the simplest amino acid) produced in the collision of neutral glycine with low-energy multiply charged ions in the gas phase. The main fragments observed experimentally result from Cα-Ccarboxyl bond cleavage. Additionally, some fragments are produced after an intramolecular rearrangement of the glycine cation, in particular the loss of a neutral water molecule following a H-migration. Moreover, this work discusses qualitatively the energy transferred to the molecule in the collision with a comparative study of the fragmentation patterns for different projectile ion charge states.

Energy transfer in collisions of metal clusters with multiply charged ions

Collisions between low-energy multiply charged ions and neutral metal clusters are an efficient method to investigate charge instabilities in finite systems. We study here the appearance size ${n}_{\mathrm{app}}(q)$ of multiply charged sodium clusters ${\mathrm{Na}}_{n}^{q+}$ with $q<~10,$ i.e., the smallest size of observation for q-fold charged clusters and its dependence on the collision parameters. The experimental results are compared with the energy transferred to the cluster during the collision, calculated with the semiclassical Vlasov equation within the jellium approximation. Experimental and theoretical data show similar trends with the collision parameters and evidence the importance of dynamical effects. These results guide further investigations for studying low excited multiply charged finite systems.

Differential cross sections for single-electron capture processes by low-energy multiply charged ions

Doubly differential cross sections, in energy and angle, for state-selective single-electron capture by Ne 3+, Ne 4+ ions from Ne, and Ne 6+ ions from He have been measured at laboratory impact energies between 60 and 600 eV and scattering angles between 0° and 5°. The measurements show that the angular distributions of the reaction channels with large energy-gain values are shifted towards larger scattering angles as would be expected. The energy-gain spectra are interpreted qualitatively in terms of the reaction window, which are calculated using the single-crossing Landau-Zener model.

Production and storage of low-energy highly charged ions by laser ablation and an ion trap.

Low-energy multiply charged ions of the refractory elements tungsten and molybdenum have been produced and stored using a novel technique that couples laser ablation with a radio-frequency ion trap. The charge states of the ions stored range from q = +1 to +4 for tungsten and from q = +1 to +6 for molybdenum. Approximately 10/sup 5/ ions with energy less than 5 x 10/sup -3/ eV/amu are stored for a period in excess of 2 s. The technique can be used to store low-energy multiply charged ions of almost any element.

COOLING AND TRAPPING OF LASER INDUCED MULTIPLY CHARGED IONS OF MOLYBDENUM

Low-energy multiply charged ions of molybdenum have been produced and stored using a novel technique which combines laser ablation and ion storage. The charge states range from q=+l to q=+6. The energy of these ions is estimated to be less than 5xlW3eV/amu with the storage time of one second. The number of stored ions is about 5 10. These findings suggest that we can now study the slow processes of low energy multiply charged ions of most elements.

Interactions of Multiply Charged Ions With Solids

Three types of low-energy interactions of multiply charged ions with solids are discussed. First the interactions of high-energy highly stripped ions moving in channels which interact only with conduction electrons and hence participate in collisions with greatly reduced center-of-mass energies. Second, charge capture to multiply charged recoil ions formed in solids by collisions of high-energy multiply charged ions. Third, effects which may occur when low-energy multiply charged ions are scattered from surfaces.