Hannover 2016 – scientific programme

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A: Fachverband Atomphysik

A 40: Precision spectroscopy of atoms and ions III (with Q)

A 40.7: Talk

Friday, March 4, 2016, 12:30–12:45, f428

Resonance ionization studies in holmium and a redetermination of its ionization potential — •Pascal Naubereit¹, Yuan Liu², Tina Gottwald¹, and Klaus Wendt¹ — ¹Institute of Physics, Mainz University, D-55128 Mainz, Germany — ²Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

The first ionization potential of Holmium as well as many other lanthanides was measured around 1978 with rather big uncertainties in the order of 5 cm⁻¹ using early methods of laser spectroscopy. Values that are much more precise are obtained by using two or three step resonance ionization spectroscopy via high lying Rydberg states and applying detailed analyses of convergence limits of different Rydberg series.

Here we report on three step resonance ionization measurements into 6snp levels with principal quantum numbers 17<n<59 converging towards the two lowest members of the ionic ground state configuration. Strong interactions with interloper states, well known for most of the lanthanides, perturb the Rydberg series below the first IP for Ho. In contrary the auto-ionizing Rydberg series, observed just above the first ionization potential, exhibits a smooth behavior in the studied range from 33<n<57. Correspondingly, the latter was used to reevaluate the first ionization potential of Holmium with an uncertainty of better than 0.1 cm⁻¹. The spectroscopic measurements, which also led to the identification of a new efficient resonant excitation scheme for holmium isotope implantation within the ECHo project, as well as the Rydberg analysis are discussed.