Berlin 2001 – wissenschaftliches Programm
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MO: Molekülphysik
MO 1: Posters Monday: Clusters, Fullerenes and Nanotubes
MO 1.14: Poster
Montag, 2. April 2001, 12:30–15:00, AT3
Velocity dependence of ionization cross sections and dissociative branching ratios of C4+ clusters in C4+ → He collisions — •marin Chabot1, romain fosse2, daniel gardes1, and karine wohrer2 — 1Institut de Physique Nucléaire, Orsay, France — 2Groupe de Physique des Solides, Paris, France
Ionization cross sections and dissociative branching ratios of C4+ clusters in C4+ → He collisions as a function of the collision velocity v (v=2, 2.6, 4 a.u) have been measured. Ionization cross sections (single, double, triple) exhibit a decrease with the velocity, more pronounced for multiionization than for single ionization. Dissociative branching ratios of doubly ionized species (following single ionization of C4+ clusters), measured on an absolute scale, exhibit various velocity dependences. The two-fragments break-up branching ratios all increase with the velocity, whereas all three and four fragments branching ratios (multifragmentation) decrease with the velocity. These results are qualitatively interpreted, as will be shown at the conference, if one assumes the two-fragments break-up to follow a pure single ionization of C4+(exclusive ionization) and multifragmentation to follow a single ionization accompanied by electron excitation (inclusive ionization) such as the two-electron ionization-excitation process.