Collective mode properties in a paired fullerene-ion plasma.
A pair-ion plasma without electrons consisting of C60+ and C60- is generated through the processes of electron-impact ionization, electron attachment, and magnetic filtering. Properties of electrostatic modes propagating along magnetic-field lines are experimentally investigated by externally exciting them with two types of electrodes. It is found that four kinds of wave modes exist and a frequency spectrum of phase lag between the density fluctuations of C60+ and C60- is unique in comparison with ordinary electron-ion plasmas. One of the modes is an ion acoustic wave which is divided into two branches at around the ion cyclotron frequency in the presence of a backwardlike mode joining them. The phase lag of the ion acoustic wave strongly depends on the frequency, while those for the other ion plasma and intermediate-frequency waves are constant at pi independent of the frequency.
Department of Electronic Engineering, Tohoku University, Sendai 980-8579, Japan. oohara@ecei.tohoku.ac.jp
W
W
Oohara
Y
Y
Kuwabara
R
R
Hatakeyama