Polarizability of helium atom can be found in many papers, for example, by Masili & Starace, PHYSICAL REVIEW A 68, 012508 (2003) (available online at http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1046&context=physicsfacpub ) -- see their Table V for static polarizability. They also calculated dynamic case in that paper. 

As for He+, it's just a hydrogen-like atom so its static polarizability can be calculated analytically, which gives 9/(2Z^4) where Z=2 (for H atom -- see derivation in many textbook, including Landau & Lifshitz Quantum Mechanics). For high-charge hydrogen-like ions, you might want to account for relativistic effect, which has been treated in many papers, for example,

Le et al, J. Phys. B: At. Mol. Opt. Phys. 27, 4083 (1994)

and dynamic polarizability 

Le et al, J. Phys. B: At. Mol. Opt. Phys 29, 2897 (1996)

Relativistic effect is negligible in Helium.

Hope that helps.

thank you very much for your help

Hi There

i need molar polarizability, known as Ar, for Helium-4 to calculate the Refractive Index n from Lorentz-Lorenz equation. Do you have any idea, where can i find that? And i dont know if that is temperature-dependent!!

Tnx for ur Help in advance

Sina H. Aghapour