Precision measurement of the ionization energy of Cs I

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Johannes Deiglmayr, Holger Herburger, Heiner Saßmannshausen, Paul Jansen, Hansjürg Schmutz, and Frédéric Merkt


Phys. Rev. A 93, 013424 (2016)

We present absolute-frequency measurements for the transitions from the 6s1/2 ground state of 133Cs to np1/2 and np3/2 Rydberg states. The transition frequencies are determined by one-photon UV spectroscopy in ultracold samples of Cs atoms using a narrowband laser system referenced to a frequency comb. From a global fit of the ionization energy EI and the quantum defects of the two series we determine an improved value of EI = hc · 31406.4677325(14) cm-1 for the ionization energy of Cs with a relative uncertainty of 5·10-11. We also report improved values for the quantum defects of the np1/2, np3/2, ns1/2, and nd5/2 series.