New even-parity fine structure levels of the Lanthanum atom discovered by means of optogalvanic spectroscopy

Abstract

Laser excitation of an Ar–La plasma, generated in a hollow cathode discharge lamp, has allowed to us observe a huge number of spectral lines that could not be interpreted as transitions between already known La energy levels. From the observed hyperfine structure patterns and fluorescence lines, we derived 37 new La levels, all with even parity, in the energy range between 38 000 cm−1 and 43 000 cm−1. The existence of these levels was then proved by excitations from other known lower levels.