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Metal-fullerene compounds are characterized by significant electron transfer to the fullerene cage, giving rise to an electric dipole moment. We use the method of electrostatic beam deflection to verify whether such reactions take place within superfluid helium nanodroplets between an embedded C 60 molecule and either alkali (heliophobic) or rare-earth (heliophilic) atoms. The two cases lead to distinctly different outcomes: C 60 Na n ( n = 1–4) display no discernable dipole moment, while C 60 Yb is strongly polar. This suggests that the fullerene and small alkali clusters fail to form a charge-transfer bond in the helium matrix despite their strong van der Waals attraction. The C 60 Yb dipole moment, on the other hand, is in agreement with the value expected for an ionic complex.
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Direct detection of polar structure formation in helium nanodroplets by beam deflection measurements
Long-range intermolecular forces are able to steer polar molecules submerged in superfluid helium nanodroplets into highly polar metastable configurations. We demonstrate that the presence of such special structures can be identified, in a direct and determinative way, by electrostatic deflection of the doped nanodroplet beam. The measurement also establishes the structures’ electric dipole moments. In consequence, the introduced approach is complementary to spectroscopic studies of low-temperature molecular assembly reactions. It is enabled by the fact that within the cold superfluid matrix the molecular dipoles become nearly completely oriented by the applied electric field. As a result, the massive (tens of thousands of helium atoms) nanodroplets undergo significant deflections. The method is illustrated here by an application to dimers and trimers of dimethyl sulfoxide (DMSO) molecules. We interpret the experimental results with ab initio theory, mapping the potential energy surface of DMSO complexes and simulating their low temperature aggregation dynamics.
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- Award ID(s):
- 1664601
- PAR ID:
- 10149387
- Date Published:
- Journal Name:
- Physical Chemistry Chemical Physics
- Volume:
- 21
- Issue:
- 37
- ISSN:
- 1463-9076
- Page Range / eLocation ID:
- 20764 to 20769
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9cp04322e
