COLLECTIVE EXCITATIONS AND OPTICAL BISTABILITY IN PARTIALLY-IONIZED HYDROGEN PLASMAS DUE TO HIGH ELECTRIC-FIELDS

The influence of an external electric field on the quantum distributio n function and, consequently, on the nonequilibrium susceptibility is investigated in random phase approximation. The dispersion relation be comes bistable for certain wave vectors in a limited field-density-tem perature plane. An instable acoustic mode is observed between two opti cal stable branches. These modes arise due to the applied field and ca n be controlled by the held strength. They are an expression of the no nequilibrium situation, which is established by an applied electric fi eld.