Combining experiments and relativistic theory for establishing accurate radiative quantities in atoms: The lifetime of the 2P3/2 state in Ca + 40

We report a precise determination of the lifetime of the (4p)2P3/2 state of Ca+40, τP3/2=6.639(42)ns, using a combination of measurements of the induced light shift and scattering rate on a single trapped ion. Good agreement with the result of a recent high-level theoretical calculation, 6.69(6) ns [M. S. Safronova, Phys. Rev. A 83, 012503 (2011)PLRAAN1050-294710.1103/PhysRevA.83.012503], but a 6-σ discrepancy with the most precise previous experimental value, 6.924(19) ns [J. Jin, Phys. Rev. Lett. 70, 3213 (1993)PRLTAO0031-900710.1103/PhysRevLett.70.3213], is found. To corroborate the consistency and accuracy of the new measurements, relativistically corrected ratios of reduced-dipole-matrix elements are used to directly compare our result with a recent result for the P1/2 state, yielding a good agreement. The application of the present method to precise determinations of radiative quantities of molecular systems is discussed.