(color online) Effects of μ and σ on the phase shift ∇Y₀ due to the interaction between two ((a) and (b)), four ((c) and (d)), and six (1(e) and (f)) equal amplitude IA solitons for non-relativistic helium light ions with α = 5/3, ultra-relativistic (γ = 4/3), and non-relativistic (γ = 5/3) electrons and positrons, respectively, where η₁ = 0.6, λ = 0.1, β = 0.1, k₁ = 1, k₂ = 2, k₃ = 3 and ε = 0.1.