The first ionization potential (IP) of technetium (Tc) has been determined by evaluating Rydberg convergences toward the first ionization potential as well as toward two low-lying excited states of the singly charged Tc ion. The Rydberg states were excited and detected by applying multiphoton resonance ionization mass spectrometry (RIMS) on the long-lived isotope ${}^{99g}$Tc using a three-color excitation scheme. The observed Rydberg convergences yield a result for the first ionization potential of Tc $V_{\mathrm{IP}}(\mathrm{Tc})=7.119380(32)$ eV. This precise value for $V_{\mathrm{IP}}(\mathrm{Tc})$ is somewhat lower than the so far published data of $7.23$ eV or $7.28$ eV, dating back to the 1950s.

• Received 22 February 2010

DOI:https://doi.org/10.1103/PhysRevA.81.052513