He3binding energy in thin helium-mixture films

We report measurements of the binding energy of dilute coverages of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ to ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ adsorbed films. These energies, when combined with measurements of the energy gap between the ground state and the first excited state of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ film, provide the binding of the excited state to the film surface. We find that for 0.1 monolayer of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ areal densities, 0.21≤${\mathit{n}}_4$≤0.53 A${\mathrm{̊}}^{\mathrm{-}2}$, the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ binding energies obtained are in reasonable agreement with values calculated using a density functional description of the film for the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ coverage dependence of the binding energy.