Collective mode properties in a paired fullerene-ion plasma

Area of Science:

• Plasma Physics
• Condensed Matter Physics
• Materials Science

Background:

• Electron-ion plasmas are well-studied, but pair-ion plasmas offer unique properties.
• Fullerenes (C60) can form both positive (C60+) and negative (C60-) ions, enabling pair-ion plasma creation.

Purpose of the Study:

• To experimentally investigate electrostatic modes in a C60+ and C60- pair-ion plasma.
• To characterize the frequency spectrum and phase lag of wave modes.
• To compare these properties with those of traditional electron-ion plasmas.

Main Methods:

• Generation of a pair-ion plasma using electron-impact ionization, electron attachment, and magnetic filtering.
• Experimental excitation of electrostatic modes along magnetic field lines using two electrode types.
• Measurement of density fluctuations and phase lags between C60+ and C60-.

Main Results:

• Existence of four distinct electrostatic wave modes identified.
• Observation of a unique frequency spectrum of phase lag between C60+ and C60- density fluctuations.
• An ion acoustic wave mode was observed, splitting into two branches near the ion cyclotron frequency, with a backward-like mode connecting them.

Conclusions:

• The C60+ and C60- pair-ion plasma exhibits unique electrostatic wave properties distinct from electron-ion plasmas.
• The phase lag of the ion acoustic wave is frequency-dependent, unlike other observed ion plasma and intermediate-frequency waves.