New spin-wave modes in ${}_{}{}^3{}_{}{}^{}$He${\mathrm{-}}^4$He solution

cw NMR measurements have been made on ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He solutions of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ concentration (${\mathrm{X}}_3$) between 1.3% and 8.6%, at pressures of 0, 7, or 8 bars and at temperatures down to 0.2 mK. In the collisionless region, the NMR absorption line exhibits several satellite peaks in addition to its narrowing. Numerical analysis of the phenomenon as an excitation of standing spin-wave modes leads to the determination of the Fermi-liquid interaction parameter λ. Its concentration dependence supports the quasiparticle interaction potential proposed by Murdock, Mountfield, and Corruccini.