Mainz 1997 – wissenschaftliches Programm
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A: Atomphysik
A 10: Poster I
A 10.13: Poster
Dienstag, 4. März 1997, 16:00–18:00, Poster I
Influence of Embedded Species on the Stability of HeN− Droplets — •M. Farnik, U. Henne, B. Samelin, and J. P. Toennies — Max-Planck-Institut für Strömungsforschung Göttingen, Bunsenstr. 10, D-37073 Göttingen
Excess electrons in liquid He droplets form bubbles which are essentially metastable. For HeN− droplets of size N=105−107 we have measured lifetimes of 1−103 ms. Here we present results for He droplets which have captured foreign atoms or molecules in a pick up cell prior to electon attachment. The dependence of the autodetachment signal Sn, which represents that part of droplets which loose the excess electron, on the number of embedded particles is measured.
Embedding molecules with a positive electron affinity (SF6, O2) results in a decrease of Sn because the electrons are strongly bound to these molecules inside the liquid He droplet. Rare gas atoms have negative electron affinities. Thus the embedding of Ne and Ar leads to an increase in the autodetechmant signal Sn. For Kr and Xe we have found also an increase of Sn if only a few atoms are embedded whereas a further increase of the number of embedded atoms reduces Sn. This behaviour is explained by the fact that the embedded rare gas atoms form solid clusters within the He droplet [1] and that a critical size for Xe and Kr clusters exists above which they can capture electrons.
[1] M. Lewerenz, B. Schilling, J. P. Toennies, J. Chem. Phys. 102(20), 8191 (1995)