Laser resonance photoionization spectroscopy of Rydberg levels in Fr

Abstract

We investigated for the first time the high-lying Rydberg levels in the rare radioactive element francium (Fr). The investigations were conducted by the highly sensitive laser resonance atomic photoionization technique with Fr atoms produced at a rate of about ${10}^{3}$ atoms/s in a hot cavity. We measured the wave numbers of the 7${p}^{2}$${P}_{3/2}$\ensuremath{\rightarrow}${\mathrm{nd}}^{2}$D (n=22--33) and 7${p}^{2}$${P}_{3/2}$\ensuremath{\rightarrow}${\mathrm{ns}}^{2}$S (n=23, 25--27,29--31) transitions and found the binding energy of the 7${p}^{2}$${P}_{3/2}$ state to be T=-18 924.8(3) ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, which made it possible to establish accurately the ionization potential of Fr.