Bunermann O, Dvorak M, Stienkemeier F, Hernando A, Mayol R, Pi M, Barranco M, Ancilotto F

Experimental and theoretical results for mixed helium droplets doped with one calcium atom are reported. The absorption spectrum around the 4s4p <- 4s(2) transition is calculated as a function of the composition of the droplet and compared to the experiment. Our study reveals the distinct feature that for specific He-3 concentrations, Ca atoms sit at the He-3-He-4 interface. This particular property of Ca, likely not shared with any other atomic or molecular species but the heavier alkaline-earth atoms, might offer the possibility of using it to probe the He-3-He-4 interface of the droplet.