Nuclear charge radii of the tin isotopes from muonic atoms

The muonic atom 2p1/2-1s1/2 and 2p3/2-1s1/2 transition energies were measured with an experimental accuracy of better than 20 ppm for the isotope chain 112,114,116,117,118,119,120,122,124Sn. Precise values for the Barrett equivalent nuclear radii R_kα and their differences as well as root-mean-square radii were deduced. The {Δ}N=2 isotope shifts between the even Sn isotopes show a subshell effect at the neutron number N=64. Otherwise, there is a nearly linear decrease with increasing N, in accordance with the general systematics of nuclear charge radii. Our muonic atom results are in a good agreement with recent optical data, including odd-even staggering. Hartree-Fock calculations reproduce the general trend but not the subshell effect. Regarding the nuclear polarization corrections, the problem in the 2p splitting found earlier in μ^--Zr and μ^--Pb seems also to persist in μ^--Sn.