High-Resolution Measurements of Initial Kinetic Energy of Fragment Ions Produced in Fast Heavy Ions – C60

Abstract

High-resolution data are presented for initial kinetic energy distributions (KEDs) of fragment ions from C60 bombarded by 1.5-MeV Li+ and 6.0-MeV Si3+ ions. The KEDs were obtained by means of a peak profile analysis of time-of-flight spectra measured in coincidence with secondary electrons emitted simultaneously. It is found that the values of KE decrease monotonically with increasing cluster size; e.g., mean values are about 12 eV (C1+) and 1 eV (C11+) for Si3+ impacts. Also, we found that the KEDs for small ions Cn+ (n > 1) showed single-peak distribution patterns. The most important result obtained in this work is the double peak distribution pattern observed for C1+ ions. This newly observed structure suggests clearly that two different production mechanisms must be taken into account for the production of C1+ ions in C60-multifragmentation process.