Adsorption of sodium and cesium on aggregates of C60
1 Institut für Ionenphysik und
Angewandte Physik, University of Innsbruck, Technikerstrasse 25, 6020
2 Department of Physics, University of New Hampshire, Durham, New Hampshire 03824, USA
Received in final form: 27 July 2016
Published online: 15 September 2016
We explore the formation of C60 sodium and C60 cesium complexes in superfluid helium nanodroplets. Anomalies in mass spectra of these doped droplets reveal anomalies in the stability of ions. (C60)mCs+n ions (m ≤ 6) are particularly abundant if they contain n = 6m + 1 cesium atoms; (C60)mCs2+n dications (m ≤ 3 or 5) are abundant if n = 6m + 2. These findings are consistent with the notion that alkali metal atoms (A) transfer their valence electrons into the three-fold degenerate lowest unoccupied orbital of C60, resulting in particularly stable C60A6 building blocks. However, (C60)4CsCs2+n dications display an entirely different pattern; instead of an expected anomaly at n = 6 × 4 + 2 = 26 we observe a strong odd-even alternation starting at n = 6. Also surprising is the effect of adding one H2O or CO2 molecule to (C60)mCsn mono- or dications; anomalies shift by two units as if the impurity were acting as an acceptor for two valence electrons from the alkali metal atoms.
Key words: Clusters and Nanostructures
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