Elementary Excitations inHe3-He4Mixtures

The energy spectrum of elementary excitations in dilute ${\mathrm{He}}^3$-${\mathrm{He}}^4$ mixtures in investigated using a Feynman type of wave function. It is found that the ${\mathrm{He}}^3$ energy spectrum lies below the phonon-roton energy spectrum and exhibits a minimum near the roton minimum. Some consequences of this energy spectrum are discussed.