posted on 2024-01-26, 03:30authored byAnna Maria Reider, Jan Mayerhofer, Paul Martini, Paul Scheier, Olga V. Lushchikova
Magnesium clusters
exhibit a pronounced nonmetal-to-metal transition,
and the neutral dimer is exceptionally weakly bound. In the present
study, we formed pristine Mgnz+ (n = 1–100, z = 1–3) clusters and mixed (C60)mMgnz+ clusters (m = 1–7, z =
1, 2) upon electron irradiation of neutral helium nanodroplets doped
with magnesium or a combination of C60 and magnesium. The
mass spectra obtained for pristine magnesium cluster ions exhibit
anomalies, consistent with previous reports in the literature. The
anomalies observed for C60Mgn+ strongly suggest that Mg atoms tend to wet the surface
of the single fullerene positioning itself above the center of a pentagonal
or hexagonal face, while, for (C60)mMgnz+, the preference for Mg to position itself within the dimples formed
by fullerene cages becomes apparent. Besides doubly charged cluster
ions, with the smallest member Mg22+, we also
observed the formation of triply charged ions Mgn3+ with n > 24. The ion efficiency
curves of singly and multiply charged ions exhibit pronounced differences
compared to singly charged ions at higher electron energies. These
findings indicate that sequential Penning ionization is essential
in the formation of doubly and triply charged ions inside doped helium
nanodroplets.