Evidence for an Alignment Effect in the Motion of Swift Ion Clusters through Solids

Some new effects seen in the passage of swift ion clusters through solids

“…Our measurements reveal large and hitherto unknown departures from the results expected for clusters undergoing simple Coulomb explosions [ 2].…”

Coulomb explosion as a probe to understand the mechanism of electron stripping from ions interacting with crystalline solids

“…This effect, termed as Coulomb explosion, is observed in channeling configuration as an enhancement of the backscattering yield dechanneling when compared to atomic ions. This and other effects, as the alignment of the clusters under the effect of the electrons plasma wake, 29 vicinage, or the coherent dynamic response by the target electrons in the presence of correlated ions 3 or the alteration of the chargestate equilibrium in the presence of molecular ions, 30 have induced a vast amount of research on molecular clusters, 31 from theoretical and experimental approaches, not only because of the intrinsic interest of correlated motion of particles in a crystalline lattice and in particular their effect on the stopping power of ions but also due to their practical applications: for inertial confinement fusion in large scale facilities; 32,33 as mentioned above, for direct imaging the structure of molecules, which in contrast to traditional techniques allows the study of excited states and photochemical dynamics; 5,6,15,16 as well as the modification of materials at a nanometer scale. 7,34,35 In spite of all this research carried out up to now on the Coulomb explosion, to our knowledge, the Coulomb explosion has not been used to understand such a basic aspect of the ion-solid interaction as the process of the electron's stripping of the impinging ions.…”

“…The orientation of the molecule could be altered by the wake forces of the leading particles; but this effect is negligible in the spatial period T hkl since any reorientation of the molecule occurs after traveling very long distances: ϳ10 2 -10 3 Å for alignments of 0.1°. 29 Ergo, after only three or four spatial periods, while the ions are still in what is considered the surface, the stripping of the ions' electrons that determines the succeeding Coulomb explosion has taken place, and since the strength of the repulsive interaction during these initial states is at its peak, it determines any subsequent behavior. This means that although charge exchange may take place afterwards, by then, the particles that were composing the molecule are far apart and behaving without any mutual correlation so the imprint that the electron stripping left is permanent.…”

Coulomb Heating Behaviour of Fast Light Diclusters in Si<100> Direction

“…In particular, significant coherence effects (vicinage effects) have been predicted theoretically and in some cases experimental molecular stopping forces show clear deviations from simple additivity rules concerning the projectile constituents (Arista, 2000;Brandt et al, 1974). Other effects related to the correlated motion of cluster atoms, such as Coulomb explosion (Gemmell et al, 1975), enhanced electron emission (Rothard et al, 1990), desorption and sputtering (Matsuo et al, 1997;Yamagushi et al, 1995) have also been reported and reviewed in recent publications (Yamada et al, 2003).…”