Precision measurement of the lifetime of the $6p \mbox{ } {}^{2}P_{1/2}$ level of Yb${}^{+}$

We present a precise measurement of the lifetime of the $6p \mbox{ } {}^{2}P_{1/2}$ excited state of a single trapped ytterbium ion (Yb${}^{+}$). We use a time-correlated single photon-counting technique~\footnote{L. Young, \textit{et al}., \textit{Phys. Rev. A} \textbf{50}, 2174 (1994)} adapted to utilize the features of a single-atom system~\footnote{D. L. Moehring, \textit{et al.}, \textit{Phys. Rev. A} \textbf{73}, 023413 (2006)}. In particular, ultrafast pulses excite a single trapped Yb$^+$ ion and the emitted photons are coupled into a single-mode optical fiber. By performing the measurement on a single atom with fast excitation and excellent spatial filtering, we are able to eliminate common systematics. Among other things, experimental measurements of Yb-like ions may be used to test \textit{ab initio} atomic structure calculations~\footnote{U. I. Safronova, \textit{et al.}, \textit{Phys. Rev. A} \textbf{66}, 022507 (2002)}.