Investigation of Rydberg states of the europium atom using resonance ionization spectroscopy

We report four odd-parity Rydberg series in the spectrum of europium atoms in the energy region 45 000-45 735 cm(-1). These four series belong to tota l angular momentum quantum numbers J = 5/2, 7/2, 9/2 and 11/2 and converge to the first ionization limit S-9(4). The studies were carried out employin g the multistep resonance ionization spectroscopy technique using two pulse d dye lasers. For some of the Rydberg series we could observe the members u p to n = 67. Different stepwise excitation-ionization schemes helped us to assign a unique J quantum number up to n = 39 and enabled us to separate th e series with different values of J. The Rydberg series belonging to J = 5/ 2 was found to be quite unperturbed and was therefore used to evaluate the first ionization limit of the europium atom.