Lifetime determination of the 5d$^{2}$~$^{3}$F$_{2}$ state in barium using trapped atoms

TL;DR

This paper measures the lifetime of the metastable 5d^2 3F_2 state in barium using magneto-optical traps, confirming theoretical predictions and demonstrating the method's effectiveness for long-lived states.

Contribution

It introduces a novel experimental approach to determine the lifetime of long-lived excited states in heavy atoms using trapped atoms and fluorescence analysis.

Findings

Measured the 5d^2 3F_2 state lifetime as 160(10) μs.

Confirmed theoretical lifetime prediction of 190 μs.

Validated atomic structure calculations for heavy multi-electron systems.

Abstract

Magneto-optically trapped atoms enable the determination of lifetimes of metastable states and higher lying excited states like the $\rm{5d^{2}~^{3}F_{2}}$ state in barium. The state is efficiently populated by driving strong transitions from metastable states within the cooling cycle of the barium MOT. The lifetime is inferred from the increase of MOT fluorescence after the transfer of up to $30\,\%$ of the trapped atoms to this state. The radiative decay of the $\rm{5d^{2}~^{3}F_{2}}$ state cascades to the cooling cycle of the MOT with a probability of $96.0(7)\,\%$ corresponding to a trap loss of $4.0(7)\,\%$ and its lifetime is determined to $\rm{160(10)~\mu s}$. This is in good agreement with the theoretically calculated lifetime of $\rm{190~\mu s}$ [J. Phys. B, {\bf 40}, 227 (2007)]. The determined loss of $4.0(7)\,\%$ from the cooling cycle is compared with the theoretically calculated branching ratios. This measurement extends the efficacy of trapped atoms to measure lifetimes of higher, long-lived states and validate the atomic structure calculations of heavy multi-electron systems.