E.S. Parilis

Acceleration of Cn+60 molecules to high energy

Abstract For the first time fullerene ions have been accelerated to high energy (4–36 MeV). Negative ions of C − 60 were produced in an ion source with a Cs gun and injected into a tandem accelerator. The change of charge from negative to positive was achieved by collisions with N 2 molecules in a gas cell at the high voltage terminal before the second acceleration step. To identify the accelerated molecular ions, the injected beam was pulsed, and time-of-flight measurements combined with energy measurements allowed mass and charge assignments.

Emission of hydrogen ions under multiply charged ion bombardment

Abstract The emission yield of hydrogen ions emitted from a solid surface under multiply charged ion bombardment increases rapidly with the incident charge state. This trend has been observed with slow (keV energy range) and fast (MeV energy range) projectiles. A model of Coulomb explosion of a surface charged small domain is proposed to explain the H + emission yield. A comparison with the experimental results is given and energy distributions are calculated. Further experiments are proposed to confirm the model.

Secondary Electron Emission Yields from a CsI Surface Under Impacts of Large Molecules at Low Velocities (5 × 103−7 × 104 ms−1)

The yields of electron emission from a CsI surface bombarded with very heavy molecular ions have been measured by coincidence counting in time-of-flight mass spectrometry. These ions were produced by the matrix-assisted laser desorption/ionization technique. The masses ranged from 700 to 66 000 Da with velocities V between 5 × 103 and 7 × 104 ms−1. An electron emission rate of a few per cent was measured for the smaller impact velocities. The variations of the electron yields with mass and velocity are compared to previous data and analysed by different models. A sublinear mass dependence is observed as well as a V4 dependence at low velocity.

SUBLINEAR EFFECT IN ELECTRON EMISSION FROM SOLIDS BOMBARDED WITH SWIFT GOLD CLUSTERS

Abstract A sublinear effect in the secondary electron emission from insulating solids under impacts of gold clusters (Au) n , n = 1–5, with energy E = 33–11000 keV/atom has been observed experimentally using the ARAMIS and Tandem accelerators at Orsay. The effect manifests itself in the decrease of the number of emitted electrons per cluster atom with the increase of the number of atoms in the cluster and the projectile energy. We explain this phenomenon by a mechanism of sweeping-out electrons, which causes a decrease in the number of available electrons in the solid, after the passage of the forward atoms of the cluster through the atomic layers from which the electrons can be emitted. Calculated absolute values of the sublinear effect as well as its dependencies, based on the theory of secondary electron emission, are in agreement with the experimental data.

Radiation effects under multiply charged ion impacts

Abstract In experiments by a joint group of Livermore Sandia National Laboratories, and Kansas State University and a group of Lawrence Livermore National Laboratory some nanometer-size shallow craters and blisters on mica surface exposed to Xe 44+ bombardment have been observed. No ion energy dependence of their size was recorded. The electrostatic Coulomb repulsion is an appropriate model to describe the origin of shallow circular features on mica surface. The protruding bumps are created after the binding forces between cations and former anions disappear due to local charge depletion during the near surface Auger neutralization of slow highly charged ion.

Sweeping-out-electrons effect under impact of large molecules and clusters

This paper presents a review of one of the most intriguing effects of non-additivity under impacts of polyatomic molecules and clusters, observed up to now only in a variety of electronic energy loss phenomena: electron emission, luminescence, projectile charge state formation, electron–hole pairs generation and the high-energy part of sputtering under cluster impacts. The sublinear effects consist in decreasing yields per atom with increasing number of cluster constituents. The reduction is caused by the mechanism of sweeping-out-electrons that removes some electrons from the cluster trek in binary collisions between the front running cluster atoms and the target atoms, leaving fewer available for the tailing ones. In addition to the pioneering experimental studies performed at IPN, Orsay, these and similar effects were observed in many laboratories and are thought to be the expressions of a general mechanism. 2002 Elsevier Science B.V. All rights reserved.

Evidence of Coulomb explosion sputtering of ultra-thin Pt films due to impact of multi-charged Ar ions

The phenomenon of potential sputtering of ultra-thin Pt films due to impact of 20 keV highly charged

Atomic collisons with accelerated fullerenes

Ar^{q+}

The study of graphite disordering using the temperature dependence of ion induced electron emission

(q = 3 - 8) ions has been investigated. The results show enhanced erosion of the Pt film with the increase of potential energy of the Ar projectile.Abstract The phenomenon of Coulomb sputtering of ultra-thin Pt films due to impact of 20 keV highly charged Ar q + ( q =3–8) ions has been investigated. The results show enhanced erosion of the Pt film with the increase of potential energy of the Ar projectile.

Ion-induced electron emission - monitoring the structure transitions in graphite

Abstract An estimation of multiple ionization of 10 MeV fullerenes in C60− → N2 collisions based on binary encounter model has been carried out taking into account plural collisions between nitrogen and carbon atoms, and the stability of the multiply charged fullerene.