Precision spectroscopy of a trapped $^{173}$Yb$^+$ ion using a bath of ultracold atoms

Abstract

We demonstrate precision laser spectroscopy of a trapped $^{173}$Yb$^+$ ion that is not directly laser cooled by coupling it to ultracold atoms. The atomic bath continuously cools the internal degrees of freedom of the ion to its hyperfine ground state via spin-exchange collisions. Successful laser excitation is detected via state-selective charge transfer and subsequent ion loss. We probe the $6^2S_{1/2}\rightarrow 6^2P_{3/2}$ transition at 329 nm and measure the magnetic and electric hyperfine interaction constants for the $6^2P_{3/2}$ state to be $A=-241(1)$ MHz and $B=1460(8)$ MHz, respectively. Our results are in agreement with a previous measurement obtained in a hollow-cathode discharge experiment but are a factor of 6-9 more precise. The techniques demonstrated in this work may be extended to perform precision spectroscopy on other ions with complex level structures.

Figures (4)

• Figure 1: The level scheme of $^{173}$Yb$^{+}$ (not to scale). We probe the $^{2}S_{1/2} \rightarrow {}^{2}P_{3/2}$ transition using a sequence of 329 nm laser pulses, after which the ion has a considerable probability to spontaneously decay (wavy lines) into one of the metastable states $^2D_{3/2}$ or $^2D_{5/2}$ and subsequently end up in the extremely long-lived $^2F_{7/2}$ state. This leads to a highly probable charge transfer collision with a $^6$Li atom, resulting in ion loss. The time between pulses is set to allow the ion to be cooled back to the $F=3$ ground state via a spin-exchange collision with a $^6$Li atom. In this way, leakage out of the 329 nm cycle by spontaneous decay into the $F=2$ state is eliminated.
• Figure 2: Setup schematics. Laser beams are focused into the center of the Paul trap, where the cloud of Li atoms is loaded into ODT. The inset shows a fluorescence image of a two ion crystal composed of a dark ion ($^{173}$Yb$^+$ ) and a bright ion ($^{174}$Yb$^+$).
• Figure 3: The ion-loss spectrum of $^2S_{1/2}\rightarrow {}^2P_{3/2}$ transition in $^{173}$Yb$^+$ from $F=3$ to $F'=\{2,3,4\}$. The data is fitted by a sum of Lorentzian functions. The experimental data points represent an average of at least 20 experimental realizations and error bars denote the standard error.
• Figure 4: (a) Energy levels and relevant transitions in $^{171}$Yb$^{+}$ (not to scale). Straight lines represent the processes induced by the lasers, and wavy lines those by spontaneous emission. (b) Frequency scan of the $^2S_{1/2}\rightarrow {}^2P_{3/2}$ transition in $^{171}$Yb$^+$ from $F=0$ to $F'=1$: with a single ion (black) and atoms (red). The data is fitted by Lorentzian functions. The experimental data points represent an average of at least 20 experimental realizations and error bars denote the standard error.