Experimental and theoretical study of the 3d 2D-level lifetimes of 40Ca+ -: art. no. 032504

We report measurements of the lifetimes of the 3d D-2(5/2) and 3d D-2(3/2) metastable states of a single laser-cooled Ca-40(+) ion in a linear Paul trap. We introduce a measurement technique based on high-efficiency quantum state detection after coherent excitation to the D-5/2 state or incoherent shelving in the D-3/2 state, and subsequent free, unperturbed spontaneous decay. The result for the natural lifetime of the D-5/2 state of 1168(9) ms agrees excellently with the most precise published value. The lifetime of the D-3/2 state is measured with a single ion and yields 1176(11) ms which improves the statistical uncertainty of previous results by a factor of four. We compare these experimental lifetimes to high-precision ab initio all order calculations [D-3/2 state: 1196(11) ms; D-5/2 state: 1165(11) ms] and find a very good agreement. These calculations represent an excellent test of high-precision atomic theory and will serve as a benchmark for the study of parity nonconservation in Ba+ which has similar atomic structure.