Observations of low-frequency mode in a multicomponent plasma with negative ions

Based on linear perturbation theory, a dispersion relation for low-frequenc y (LF) electrostatic waves has been derived in a multicomponent plasma cont aining negative ions. To relate the theoretical observations with experimen ts on the LF wave, the slower mode has been studied extensively for various plasma models. The experiment was carried out in Ar, F, and electron plasm a in a double plasma device. The experimental observations on LF electrosta tic waves yield the qualitative frequency variations due to the presence of negative ions. In the region of lower negative ion concentration, the mode decreases with the addition of a higher percentage of negative ion concent ration while later, in the higher region of negative ion concentration, the variation shows the asymptotic behavior with negative ion concentration. B oth the observations, theoretical and experimental, have shown a good agree ment with each other. Moreover, a theoretical model of plasma with heavy ne gative ions has also been presented. (C) 1999 American Institute of Physics . [S1070-664X(99)02905-5].