Laser cooling and quantum jumps of a single indium ion.

Abstract

We performed laser spectroscopy of ${\mathrm{In}}^{+}$ ions stored in a radio-frequency trap. The 5${\mathit{s}}^{2}$ $^{1}$${\mathit{S}}_{0}$\ensuremath{\rightarrow}5s5p $^{3}$${\mathit{P}}_{1}$ transition at 230.6 nm was excited and its hyperfine splitting and isotope shift have been measured. The lifetime of the $^{3}$${\mathit{P}}_{1}$ state was measured using intensity modulated laser excitation: \ensuremath{\tau}${(}^{3}$${\mathit{P}}_{1}$)=0.44(4) \ensuremath{\mu}s. A single indium ion was laser cooled using this intercombination line and dark periods in the fluorescence were observed when the metastable $^{3}$${\mathit{P}}_{0}$ state was populated by a magnetic dipole decay from $^{3}$${\mathit{P}}_{1}$. The radiative lifetime of the forbidden transition $^{3}$${\mathit{P}}_{0}$${\ensuremath{\rightarrow}}^{1}$${\mathit{S}}_{0}$ was determined from the duration of the dark periods: \ensuremath{\tau}${(}^{3}$${\mathit{P}}_{0}$)=0.14(2) s. This value is compared to calculations based on perturbation theory. Prospects for an optical frequency standard using the narrow 5${\mathit{s}}^{2}$ $^{1}$${\mathit{S}}_{0}$\ensuremath{\rightarrow}5s5p $^{3}$${\mathit{P}}_{0}$ resonance at 236.5 nm of a single laser-cooled indium ion are discussed.