The ionization potentials of neutral osmium and iridium atoms have been obtained by mass-analyzed optical-optical double resonance spectroscopy. Observation of the photoionization threshold yielded approximate values of 68 058±2 ${\mathrm{cm}}^{\mathrm{-}1}$ for Os I and 72 324±2 ${\mathrm{cm}}^{\mathrm{-}1}$ for Ir I. In addition, high-lying ns and nd Rydberg series were recorded and fit by a Rydberg formula in order to obtain independent values of the ionization potentials. The results were 68 058.9±1.6 ${\mathrm{cm}}^{\mathrm{-}1}$ for Os I and 72 323.9±1.8 ${\mathrm{cm}}^{\mathrm{-}1}$ for Ir I.

• Received 23 August 1996

DOI:https://doi.org/10.1103/PhysRevA.55.1526