We present systematic results, based on density functional calculations, for the structure and energetics of
3He and
4He nanodroplets doped with alkaline earth atoms. We predict that alkaline earth atoms from Mg toBa go to the center of
3He drops, whereas Ca, Sr, and Ba reside in a deep dimple at the surface of
4He drops,and Mg is at their center. For Ca and Sr, the structure of the dimples is shown to be very sensitive to theHe-alkaline earth pair potentials used in the calculations. The 5s5p
![](/images/entities/larr.gif)
5s
2 transition of strontium atomsattached to helium nanodroplets of either isotope has been probed in absorption experiments. The spectrashow that strontium is solvated inside
3He nanodroplets, supporting the calculations. In the light of our findings,we emphasize the relevance of the heavier alkaline earth atoms for analyzing mixed
3He-
4He nanodroplets,and in particular, we suggest their use to experimentally probe the
3He-
4He interface.