Mixed Cluster Ions of Magnesium and C₆₀

Area of Science:

• Atomic and Molecular Physics
• Materials Science
• Nanotechnology

Background:

• Magnesium clusters show a significant nonmetal-to-metal transition.
• The neutral magnesium dimer is weakly bound.
• Understanding cluster formation is key to materials science.

Purpose of the Study:

• To investigate the formation and structure of pristine magnesium (Mg_n^z+) and fullerene-magnesium ((C₆₀)_mMg_n^z+) clusters.
• To analyze the behavior of magnesium atoms on fullerene surfaces.
• To explore the formation pathways of multiply charged cluster ions.

Main Methods:

• Formation of Mg_n^z+ and (C₆₀)_mMg_n^z+ clusters via electron irradiation of doped helium nanodroplets.
• Mass spectrometry to analyze cluster composition and abundance.
• Ion efficiency curve analysis to understand ionization processes.

Main Results:

• Observed anomalies in mass spectra of pristine magnesium clusters.
• Determined Mg atom positioning on C₆₀ surfaces: wetting on faces for single C₆₀, dimple-filling for multiple C₆₀.
• Identified formation of doubly (Mg₂²⁺) and triply (Mg_n³⁺, n>24) charged ions.

Conclusions:

• Mg atom arrangement depends on the number of fullerene cages.
• Sequential Penning ionization is crucial for forming multiply charged ions in helium nanodroplets.
• The study provides insights into cluster stability and growth dynamics.