Combined experimental and theoretical probe of the lifetime of the3d2D5/2state in40

Abstract

In light of the diverse range of reported values for the lifetimes of metastable states of 40Ca+, we have carried out afresh both measurements and theoretical investigation to confirm the lifetime of its 3d 2D5/2 state (T3rf5/2). A high-efficiency quantum state detection method by monitoring the quantum jumps of a laser-cooled single Ca+ ion in a miniature ring Paul trap was employed in the measurement. Also, sophisticated calculations were performed considering higher order nonlinear terms in the relativistic coupled-cluster (RCC) method with all possible single and double excitations, but accounting only for the important triple excitations from both the core and the valence orbitals. Systematic factors affecting measurement, such as collision with background gases, heating effects, the power of the 866-nm laser, and state detection errors were carefully analyzed. Our observational and theoretical values for r}d5/2 are 1174(10) ms and 1172 (3) ms, respectively, which agree well with the experimental results reported by P. A. Barton et at. [Phys. Rev. A 62, 032503 (2000)] and A. Kreuter etal. [Phys. Rev. A 7 1 ,032504 (2005)]. The present theoretical analysis demonstrates that the contributions from the core triples and Breit interaction are notable, as they improve the theoretical results obtained in the previous RCC calculations [B. K. Sahoo, Phys. Rev. A 74, 062504 (2006)].

Precise determination of the quadrupole transition matrix element ofCa+40via branching-fraction and lifetime measurements

“…Figure 4 shows a comparison of recently measured and calculated lifetimes, where our new result has improved the best previous measured result of Ref. [6] by a factor of 2.…”

“…In summary, with the development of single ion manipulation technique and laser spectroscopy methods, we have measured the 3d 2 D 5/2 state lifetime in 40 Ca + , which is τ 5/2 = 1.1652(46) s, with the uncertainty of 0.4%, a factor of 2 improvement over the best previous measurement [6]. Meanwhile, for the first time, we have measured the branching ratio for the decay 3d 2 D 5/2 → 4s 2 S 1/2 as 0.9992(80).…”

“…In our experiment, the 397 nm and 866 nm lasers for the cooling circle are commercial semiconductor ones, which may contain other spectrum components that can induce unwanted excitations. Compared to our previous work [6], three improvements are made to reduce the influence on the measured lifetime. The first improvement is the use of a 406-nm narrow-band optical filter that is inputted in the 397-nm route to filter the 393-nm spectrum component contained in the 397-nm laser's spectrum.…”

“…A trapped 40 Ca + ion has also been used for precision measurements to test atomic many-body theories [5,6,7]. Such measurements include lifetimes of some low-lying states in 40 Ca + [5,6], branching ratios [8], and dipole transition matrix elements [9].…”

“…With our measured branching ratio and lifetime, we can now extract, for the first time, the experimental values of the 4s 2 S 1/2 ↔ 3d 2 D 5/2 quadrupole transition rate and transition matrix element (in absolute value), which are, respectively, 0.8575(76) s −1 and 9.737(43) ea [6]. In summary, with the development of single ion manipulation technique and laser spectroscopy methods, we have measured the 3d 2 D 5/2 state lifetime in 40 Ca + , which is τ 5/2 = 1.1652(46) s, with the uncertainty of 0.4%, a factor of 2 improvement over the best previous measurement [6].…”