Velocity correlated emission of secondary clusters by a single surface impact of a polyatomic ion: a new mechanism of cluster emission and subpicosecond probing of extreme spike conditions.

Emission of secondary clusters off clean solid surfaces following the impact of a projectile ion at kiloelectronvolt (keV) kinetic energies is important from both practical and fundamental points of view. Understanding the underlying emission mechanisms using different types and sizes of projectile ions is therefore of high interest. In this perspective article we provide an up-to-date review of our recently observed new mechanism of velocity correlated cluster emission (VCCE) describing the emission of large clusters off different targets following the impact of a large polyatomic ion (C).

Emission of velocity-correlated clusters in fullerene-solid single collision and diagnostics of the impact energized subsurface nanovolume.

We have measured kinetic energy distributions (KEDs) of large clusters emitted from five different solid targets following a single impact of C ion at 14 keV kinetic energy. It was found that all the large clusters emitted from a given target move with nearly the same velocity and that their KEDs can be described by a thermal distribution riding on a common center-of-mass velocity (shifted Maxwellian) of some precursor. This behavior is in sharp contrast to that observed when the incoming projectile ion is monoatomic.

Direct experimental observation of a new mechanism for sputtering of solids by a large polyatomic projectile: velocity-correlated cluster emission.

We have measured kinetic energy distributions of Ta(n)C(n)(+) (n=1-10) and Ag(n)(+) (n=1-9) cluster ions sputtered off Ta and Ag targets, following impact of C(60)(-) at 14 keV kinetic energy. A gradual increase of the most probable kinetic energies with increased size of the emitted cluster was observed (nearly the same velocity for all n values). This behavior is in sharp contrast to that reported for cluster emission induced by the impact of a monoatomic projectile.

The dynamics of endohedral complex formation in surface pick-up scattering as probed by kinetic energy distributions: experiment and model calculation for Cs@C60+.

Endohedral Cs@C60 molecules were formed by implanting low energy (E0 = 30-220 eV) Cs+ ions into C60 molecules adsorbed on gold. Both growth and etching experiments of the surface deposited C(60) layer provide clear evidence for a submonolayer coverage. The Cs+ penetration and Cs@C60 ejection stages are shown to be a combined, single collision event.