STRUCTURAL-PROPERTIES OF THE NEGATIVE STRONTIUM ION - BINDING-ENERGY AND FINE-STRUCTURE SPLITTING

The binding energy and fine-structure splitting of the ground state of the Sr- (5s(2)5p P-2) ion have been measured by means of the laser ph otodetachment threshold technique combined with state-selective detect ion of neutral atoms using resonant ionization spectroscopy. We find b inding energies of 32.17+/-0.03 meV (J=3/2) and 52.06+/-0.06 meV (J=1/ 2), yielding a fine-structure splitting of 19.89+/-0.07 meV. This repr esents an improvement of two orders of magnitude compared to the recen t data based on a combination of laser photodetachment and accelerator mass spectroscopy [D. Berkovits et al., Phys. Rev. Lett. 75, 414 (199 5)].