Abstract
We report on the formation and ionization of cesium and C60Cs clusters in superfluid helium nanodroplets. Size distributions of positively and negatively charged (C60)mCsn± ions have been measured for m ≤ 7, n ≤ 12. Reproducible intensity anomalies are observed in high-resolution mass spectra. For both charge states, (C60)mCs3± and (C60)mCs5± are particularly abundant, with little dependence on the value of m. Distributions of bare cesium cluster ions also indicate enhanced stability of Cs3± and Cs5±, in agreement with theoretical predictions. These findings contrast with earlier reports on highly Cs-doped cationic fullerene aggregates which showed enhanced stability of C60Cs6 building blocks attributed to charge transfer. The dependence of the (C60)mCs3– anion yield on electron energy shows a resonance that, surprisingly, oscillates in strength as m increases from 1 to 6.
Highlights
Since the successful development of methods to synthesize fullerenes in macroscopic quantities, the properties of metaldoped fullerene solids and their potential applications have been studied
In a recent report we presented ion abundances of (C60)mCsn+ cations prepared in the gas phase by electron ionization of helium nanodroplets doped with C60Na3+ and (C60) and Cs.[8]
A key finding was that (C60)mCsn+ ions (m ≤ 6) are abundant if they contain n = 6m + 1 cesium atoms; (C60)mCsn2+ dications were abundant (with the exception of (C60)4Csn2+) if n = 6m + 2. By and large these results were consistent with earlier photoionization experiments by Martin and co-workers involving potassium and rubidium which indicated that up to six alkali metal atoms per C60 transfer their valence electrons into the t1u orbital, resulting in stable C60A6 building blocks.[9,10]
Summary
Since the successful development of methods to synthesize fullerenes in macroscopic quantities, the properties of metaldoped fullerene solids and their potential applications have been studied. In a recent report we presented ion abundances of (C60)mCsn+ cations prepared in the gas phase by electron ionization of helium nanodroplets doped with C60 and Cs.[8] A key finding was that (C60)mCsn+ ions (m ≤ 6) are abundant if they contain n = 6m + 1 cesium atoms; (C60)mCsn2+ dications were abundant (with the exception of (C60)4Csn2+) if n = 6m + 2 By and large these results were consistent with earlier photoionization experiments by Martin and co-workers involving potassium and rubidium which indicated that up to six alkali metal atoms per C60 transfer their valence electrons into the t1u orbital, resulting in stable C60A6 building blocks.[9,10] One or two additional alkali ions are needed to provide the net charge of the mono- and dications, respectively
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