Observation of the S01→P03 clock transition in Al+27

We report, for the first time, laser spectroscopy of the S01→P03 clock transition in Al+27. A single aluminum ion and a single beryllium ion are simultaneously confined in a linear Paul trap, coupled by their mutual Coulomb repulsion. This coupling allows the beryllium ion to sympathetically cool the aluminum ion and also enables transfer of the aluminum's electronic state to the beryllium's hyperfine state, which can be measured with high fidelity. These techniques are applied to measure the clock transition frequency ν=1121015393207851(6)Hz. They are also used to measure the lifetime of the metastable clock state τ=20.6±1.4s, the ground state S01 g factor gS=-0.00079248(14), and the excited state P03 g factor gP=-0.00197686(21), in units of the Bohr magneton.