Lifetime measurement of the 5d²D_5/2 state in Ba⁺

The lifetime of the metastable 5d²D_5/2 state has been measured for a single trapped Ba⁺ ion in a Paul trap in Ultra High Vacuum (UHV) in the 10⁻¹⁰ mbar pressure range. A total of 5046 individual periods when the ion was shelved in this state have been recorded. A preliminary value ${\tau }_{D_{5/2}}=26.4\left(1.7\right)$ s is obtained through extrapolation to zero residual gas pressure.