Fragmentation of high-energy ionic hydrogen clusters by single collision with helium

Fragmentation of mass-selected 60-keV/amu-Hn+ induced by single collision with helium has been studied for various cluster sizes n (9, 13,21, 25, and 31). The absolute cross sections of the charged fragments Hp+ are measured from p equal to n-2. The deduced mass distributions are strongly different from those obtained at lower collision energy (where molecular evaporation is mainly involved) due to a strong production of ionic fragments with a size of p/n<=0.5. Moreover, the distributions for p/n< =0.5 are found to have scaling properties and to follow a power law A-τ, where A is the normalized fragment mass (p/n) and τ an exponent close to 2.6. (authors)