Anomalously hindered E2 strength B(E2;2_1^+ -> 0^+) in 16C

The electric quadrupole transition from the first 2+ state to the ground 0+ state in 16C is studied through measurement of the lifetime by a recoil shadow method applied to inelastically scattered radioactive 16C nuclei. The measured lifetime is 75 ± 23 ps, corresponding to a B(E2;2_1+ -> 0^+) value of 0.63 ± 0.19 e2fm4, or 0.26 ± 0.08 Weisskopf units. The transition strength is found to be anomalously small compared to the empirically predicted value.