Transition of ion-acoustic perturbations in multicomponent plasma with negative ions

Evolution of ion-acoustic compressive (positive) and rarefactive (negative) perturbations in a multicomponent plasma with negative ions has been investigated in a double plasma device. Transition of compressive solitons in electron-positive ion plasma, into a dispersing train of oscillations in a multicomponent plasma, when the negative ion concentration r exceeds a critical value r_c, has been observed. On the other hand, an initial rarefactive perturbation initially evolves into a dispersing train of oscillations in electron-positive ion plasma and transforms into rarefactive solitons in a multicomponent plasma when the negative ion concentration is higher than the critical value. The Mach velocity and width of the compressive and rarefactive solitons are measured. The compressive solitons in the range 0c and the rarefactive solitons in the range r>r_c have different characteristics than the Korteweg-de Vries (KdV) solitons at r=0 and modified KdV solitons at r=r_c. A nonlinear differential equation having two terms to account for the lower and higher order nonlinearity has been used to explain the observed results