Revisiting Thomson's model with multiply charged superfluid helium nanodroplets.

Area of Science:

• Atomic and Molecular Physics
• Condensed Matter Physics

Background:

• Superfluid helium droplets are studied for their unique properties when multiply charged.
• Existing models often simplify charge distribution or neglect the ion solvation shell.

Purpose of the Study:

• To determine the minimum radius of superfluid helium droplets capable of hosting multiply charged ions.
• To develop a model that accurately describes ion behavior and stability within these droplets.

Main Methods:

• Utilized density functional theory to calculate cation solvation energy in helium.
• Incorporated Coulomb repulsion energy between ions.
• Developed a model that accounts for the solid-like helium shell around ions, moving beyond the liquid drop model.

Main Results:

• Identified a threshold droplet radius (R0) below which droplet energy exceeds that of separated components.
• Found that energy barriers prevent immediate Coulomb explosion, but decrease with smaller radii.
• Determined a critical radius (Rexpl) for Coulomb explosion, showing insensitivity to ion species.
• Calculated Rexpl values exhibit correct scaling with ion number compared to experiments.

Conclusions:

• The developed model provides a more realistic description of charged superfluid helium droplets.
• The findings are applicable to both cation-doped and intrinsically multicharged helium droplets (e.g., with He3+ ions).
• The model's predictions for critical radii align well with experimental observations.