We report spectroscopic and time-resolved experimental observations to characterize the $[{ \rm Xe}]4f^{ 13}(^2F^{ o}_{ 5/2}){ 5d6s(}{ ^1\!D}){ ^{ 1}[5/2]^{ o}_{ 5/2}}$ state in $^{ 172}$Yb$^+$ ions. We access this state from the metastable $4f^{ 14}5d (^2D_{ 3/2,5/2})$ manifold and observe an unexpectedly long lifetime of $\tau=37.9(9) \,\mu$s that allows visible Rabi oscillations and resolved-sideband spectroscopy. Using a combination of coherent population dynamics, high-fidelity detection and heralded state preparation, and optical pumping methods, we measure the branching ratios to the $^{ 2}D_{ 3/2}$, $^2D_{ 5/2}$, $^2S_{ 1/2}$ states to be 0.359(2), 0.639(2), 0.0023(16), respectively. The branching ratio to the $4f^{ 13}6s^{ 2}({ ^2F}_{ 7/2})$ is compatible with zero within our experimental resolution. We also report measurements of its Land\'e g-factor and the branching ratio of the ${ ^{ 2}{ D}_{ 5/2}}$ to ${ ^{ 2}{ S}_{ 1/2}}$ decay in $^{ 172}$Yb$^+$ to be 0.188(3), improving its relative uncertainty by an order of magnitude. Our measurements pave the way to a better understanding of the atomic structure of Yb$^+$ ions, which still lacks accurate numerical descriptions, and the use of high-lying excited states for partial detection and qubit manipulation in the omg architecture.
Categories: physics.atom-ph cond-mat.quant-gas quant-ph