NEUTRAL FRAGMENT PRODUCTION INDUCED BY COLLISION OF 60-KEV U(-1)-H-25(+) CLUSTERS WITH HELIUM

We report on measurements of the neutral fragment yields resulting from the collision of 60-keV u(-1)-H-25(+) clusters with helium. The sum of the mass numbers of all the neutral fragments (S-neutral) coming from each cluster is measured. The histogram obtained can be roughly divided into three S-neutral value ranges corresponding to evaporation (2u less than or equal to S(neutral)less than or equal to 10u, even), electron capture (S-neutral=25u) and ionization (11u less than or equal to S(neutral)less than or equal to 23u, mainly). The ionization process which corresponds to both odd and even values of S-neutral appears to be involved in about 83% of the dissociation events observed. These results, and their comparison with the inclusive ionic fragment distributions previously measured, show the importance of multi-ionization of the incident cluster during the collision. Moreover, the fragmentation of the unstable multicharged cluster leads to the production of several light H-p(+) fragments (p less than or equal to 5).