The spectrum of lanthanum was photographed in the 80–1220-Å region. The configuration in La ix was established for what is to the authors’ knowledge the first time in the In i isoelectronic sequence. Four levels belonging to the odd-parity system and twenty-seven levels belonging to the even-parity system have been established. Two of the four odd-parity levels and twenty-five of the thirty-two even-parity levels are new. We carried out least-squares-fitting and relativistic Hartree–Fock calculations to show the strong configuration interaction effects in the even-configuration system. Forty-seven lines were classified in La ix, of which thirty-seven are new lines.
© 1998 Optical Society of America