Fig. 6
From: Sympathetic cooling of molecular ions with ultracold atoms
Detuning of the cooling laser frequency for Ca (blue line) and Rb (red line) versus atom-ion separation. The lines in this figure assume the lasers are detuned by one linewidth below the bare-atom transition frequency.The ground-state polarizability of the Ca (Rb) atom is larger (smaller) than the excited state, leading to blue-shifting (red-shifting) of the transition frequency as the ion approaches. The blue (red) bars show the distance a Ca (Rb) atom would travel during a collision with a ∼150 amu ion at 10 mK during one excited state lifetime