Berlin 2001 – wissenschaftliches Programm

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MO: Molekülphysik

MO 1: Posters Monday: Clusters, Fullerenes and Nanotubes

MO 1.7: Poster

Montag, 2. April 2001, 12:30–15:00, AT3

Dissociation of molecular cluster and dimer ions — •Rajendra Parajuli, Sara Matt, Aleksander Stamatoviv, Paul Scheier, and Tilmann Maerk — Institut fuer Ionenphysik, Universitaet Innsbruck, A-6020 Innsbruck

Using a two sector field mass spectrometer in combination with cluster source and an electron impact ion source we have analysed dissociation reactions of cluster ions. In particular we have studied with the MIKE scan technique the kinetic energy release distribution (KERD) for spontaneously decaying stoichiometric and non-stoichiometric oxygen and nitrogen cluster ions. From (i) the shape of the KERD’s, from (ii) the binding energies deduced from these KERD’s by using finite heat bath theory and from (iii) the dependence of these data on cluster size it appears that small cluster ions decay as expected via electronic pre- dissociation whereas the large cluster ions show vibrational predissociation. In addition to monomer evaporation also other decay channels are observed for the first time. In order to shed more light onto the various reactions we measured the decay processes not in the second field free region but also with the m* method in the first field free region. By additionally varying the acceleration voltage we obtain information on apparent metastable fragmentation rates as a function of time thus enabling us to distinguish the different metastable decay mechanisms.