Disintegration of swift carbon clusters during passage through matter

Thin luminescent foils covered upstream with layers of Formvar or gold of various thicknesses were bombarded with C-8 clusters with energies between 5 and 10 MeV. The C-8 induced relative luminescence yield Phi(8) increases with growing layer thickness and approaches smoothly the value 8Phi(1), i.e., the luminescence yield induced by eight well-separated C-1 cluster constituents. This is a clear demonstration of the gradual separation between the cluster constituents during the passage of the cluster through the layers. The layer thickness necessary to separate cluster constituents far enough to act as independent atomic ions with respect to the luminescence process was calculated. The result is that Formvar layers with a thickness of about 1150 nm or approximate to250-nm-thick gold layers are necessary to establish this mutual independence of the cluster constituents. Both calculated values agree roughly with the layer thickness obtained from an extrapolation of the experimental data.