The lifetime of the Jπ=21+ state in 10C was measured using the Doppler shift attenuation method following the inverse kinematics p(10B ,n)10C reaction at 95 MeV. The 21+ state, at 3354 keV, has τ=219±(7)stat±(10)sys fs, corresponding to a B(E2)" of 8.8(3) e2 fm4. This measurement, combined with that recently determined for 10Be [9.2(3) e2 fm4], provides a unique challenge to ab initio calculations, testing the structure of these states, including the isospin symmetry of the wave functions. Quantum Monte Carlo calculations using realistic two- and three-nucleon Hamiltonians that reproduce the 10Be B(E2) value generally predict a larger 10C B(E2) probability but with considerable sensitivity to the admixture of different spatial symmetry components in the wave functions and to the three-nucleon potential used
