We report on the first experimental study of the lifetime of a bound excited state of a negative ion. A new experimental technique was developed and used to measure the radiative lifetime of the $5p^5{}^{2}P_{1/2}$ level of ${\mathrm{Te}}^{-}$. The experiment was performed in a magnetic storage ring, where a laser beam was applied along one of the straight sections. In the experiment the population of the excited $J=1/2$ level was probed each time the ${\mathrm{Te}}^{-}$ ions passed through the laser field. A decay curve was built up by sampling the population of the excited level of the ${\mathrm{Te}}^{-}$ ions as a function of time after injection into the ring. A multiconfiguration Dirac-Hartree-Fock calculation was performed in conjunction with the experiment. The calculation yielded a radiative lifetime of 0.45 s, in excellent agreement with the measured value of 0.42(5) s.

• Received 17 December 2003

DOI:https://doi.org/10.1103/PhysRevLett.92.253002