Observation of Multiple Ordered Solvation Shells in Doped Helium Droplets: The Case of HeNCa2.

Helium magic extends to 74

30 September 2023

Clusters of up to 74 helium atoms about a single ion have been produced.

Helium atoms can form clusters about a central single ion. These clusters have shell-like structures, and they are especially stable for certain ‘magic’ numbers of helium atoms. To date, magic numbers of 12, 32 and 44 have been found in experiments.

Now, a team led by researchers from University of La Laguna has found an even larger magic number of 74 for helium atoms about a calcium ion. This is probably the largest ordered structure of helium atoms about a single atom, the researchers say.

The team produced the clusters by reversing the order of previous experiments — they first ionized nanodroplets of helium and then added neutral calcium, which then became ionized inside the droplet.

A theoretical analysis indicates that the outermost shell of helium atoms forms an icosidodecahedron.

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References

1. The Journal of Physical Chemistry Letters 14, 3126−3131 (2023). doi: 10.1021/acs.jpclett.3c00224