Energy‐dependent fragmentation of polystyrene molecule using size‐selected Ar gas cluster ion beam projectile

A size‐selected Ar gas cluster ion beam (GCIB) was applied to the SIMS of a polystyrene thin film. The size of Ar cluster ions are selected between 5000 to 500 atoms at an acceleration voltage of 5 and 10 kV using time‐of‐flight technique. Under this condition, the kinetic energy per constituent atom ( E atom ) of the GCIB projectile was estimated to be 1 ∼ 20 eV. The E atom dependence of secondary ion yield of fragment species of polystyrene can be essentially classified into three types which are attributable to the relationship between the E atom and the dissociation energy of the specified bonding site of the molecule. These results indicate that the site‐specific bond breaking of molecules could be possible by adjusting the E atom of size‐selected GCIB.