Enhanced spin-dependent parity-nonconservation effect in the 7s 2S1/2 → 6d 2D5/2 transition in Fr: A possibility for unambiguous detection of the nuclear anapole moment

Employing the relativistic coupled-cluster method, comparative studies of the parity nonconserving electric dipole amplitudes for the 7s S-2(1/2) -> 6d D-2(5/2) transitions in Fr-210 and Fr-211 isotopes have been carried out. It is found that these transition amplitudes, sensitive only to the nuclear spin-dependent effects, are enhanced substantially owing to the very large contributions from the electron core-polarization effects in Fr. This translates to a relatively large and, in principle, measurable induced light shift, which would be a signature of nuclear spin-dependent parity nonconservation that is dominated by the nuclear anapole moment in a heavy atom like Fr. A plausible scheme to measure this quantity using the Cyclotron and Radioisotope Center (CYRIC) facility at Tohoku University has been outlined.