FRAGMENTATION OF HIGH-ENERGY IONIC HYDROGEN CLUSTERS BY SINGLE COLLISION WITH HELIUM

Fragmentation of mass-selected 60-keV u-1-H(n)+ induced by single coll ision with helium has been studied for various cluster sizes (n = 9, 1 3, 21, 25 and 31). The absolute cross sections of the charged fragment s H(p)+ are measured from p = 3 to n - 2. The deduced mass distributio ns are markedly different to those obtained at lower collision energy (where molecular evaporation is mainly involved) due to a strong produ ction of ionic fragments with a size of p/n less-than-or-equal-to 0.5. Moreover, the distributions for p/n less-than-or-equal-to 0.5 are fou nd to have scaling properties and to follow a power law A(-tau), where A is the normalized fragment mass (p/n) and tau an exponent close to 2.6.