Spectroscopy of Os- and a route to laser-cooled negative ions

The characteristics of atomic anions differ heavily from cations and neutral atoms, preventing the optical manipulation of their motion, with the remarkable exception of Os-. Since the negative osmium ion exhibits a bound-bound electric-dipole transition, we are currently exploring this unique feature with the aim of laser cooling. In the course of our experiments, we performed high-resolution laser spectroscopy on the relevant transition determining its frequency, cross-section and sub-level splitting in magnetic fields.