Interaction of Helium Rydberg State Molecules with Dense Helium

Area of Science:

• Atomic and Molecular Physics
• Quantum Chemistry
• Condensed Matter Physics

Background:

• The He₂^* excimer is crucial for understanding interactions in dense helium.
• Previous studies have explored its electronic states and interaction potentials.

Purpose of the Study:

• To present interaction potentials for He₂^* electronic states (a³Σ_u, b³Π_g, c³Σ_g, d³Σ_u).
• To investigate the behavior of the ³d state excimer in dense helium.
• To compare calculated fluorescence shifts with experimental data.

Main Methods:

• Bosonic density functional calculations were employed.
• Interaction potentials were analyzed for symmetry and short-range features.
• Pressure-induced fluorescence band shifts were calculated and compared to experimental corona discharge results.

Main Results:

• Interaction potentials exhibit short-range minima and unusual long-range maxima due to electrostatic attraction and Pauli repulsion.
• The ³d state excimer forms localized solvation bubbles in dense helium (4.5 K), with radii decreasing under pressure.
• Calculated ³d → ³b fluorescence shifts align well with experimental data.

Conclusions:

• The study elucidates the complex interaction potentials of He₂^* excimers.
• Solvation effects significantly influence excimer behavior in dense helium.
• Fluorescence spectroscopy of this transition probes the surrounding dense helium, not the discharge zone itself.