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${\mathit{s}}^2$ ${}_{}{}^1{}_{}{}^{}$ ${\mathit{S}}_0$→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: τ${(}^3$ ${\mathit{P}}_1$)=0.44(4) μs. 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 ${}_{}{}^3{}_{}{}^{}$ ${\mathit{P}}_0$ ${\to }^1$ ${\mathit{S}}_0$ was determined from the duration of the dark periods: τ${(}^3$ ${\mathit{P}}_0$)=0.14(2) s. This value is compared to calculations based on perturbation theory. Prospects for an optical frequency standard using the narrow 5${\mathit{s}}^2$ ${}_{}{}^1{}_{}{}^{}$ ${\mathit{S}}_0$→5s5p ${}_{}{}^3{}_{}{}^{}$ ${\mathit{P}}_0$ resonance at 236.5 nm of a single laser-cooled indium ion are discussed.