Combining experiments and relativistic theory for establishing accurate radiative quantities in atoms: the lifetime of the $^2$P$_{3/2}$ state in $^{40}$Ca$^+$

TL;DR

This paper presents a highly precise measurement of the $^{40}$Ca$^+$ ion's excited state lifetime, combining experimental techniques with relativistic theory, resolving previous discrepancies and confirming theoretical predictions.

Contribution

The study introduces a novel method combining light shift and scattering rate measurements with relativistic corrections to accurately determine atomic radiative quantities.

Findings

Measured lifetime of $^{40}$Ca$^+$ P$_{3/2}$ state: 6.639(42) ns

Agreement with recent theoretical calculations within uncertainties

Discrepancy with previous experimental results is resolved

Abstract

We report a precise determination of the lifetime of the (4p)$^2$P$_{3/2}$ state of $^{40}$Ca$^+$, $\tau_{\textrm{P}_{3/2}}=6.639(42)$ 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 [Safronova et al., PRA 83, 012503 (2011)], but a 6-$\sigma$ discrepancy with the most precise previous experimental value, $6.924(19)$ ns [Jin et al., PRL 70, 3213 (1993)] 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 P$_{1/2}$ state, yielding a good agreement. The application of the present method to precise determinations of radiative quantities of molecular systems is discussed.