Variation of the Observed Widths of La I Lines with the Energy of the Upper Excited Levels, Demonstrated on Previously Unknown Energy Levels

Abstract

We performed systematic laser spectroscopic investigations of La I spectral lines, using optogalvanic detection. Sixteen previously unknown even parity levels, having energies between 40,300 and 44,300 cm −1 , are reported. These levels classify altogether 67 lines, not listed in spectral tables. The new levels were found due to the observation of the depopulation of the lower levels of the excited transitions. We found a remarkable variation of the observed widths of single hyperfine structure components dependent on the energy of the upper excited levels. Some levels having energies higher than 43,000 cm −1 appear to have a very high ionization probability.

Progress in Finding New Energy Levels Using Laser Spectroscopy

“…If the upper level of transition 1 is close to the ionization limit, its ionization probability may be large, leading to a good OG signal but a decrease of the intensity of LIF-line 1, in some cases not distinguishable from noise. This situation is usually true for even La-levels with energies larger than 41,000 cm −1 (limit 44,981 cm −1 [3]). The observed linewidth is influenced by collisional broadening and can vary with the level energy (see [4]).…”

“…Despite the usual meaning that the fine structure energy levels of nearly all atoms (and their ions with a low number of removed electrons) have been known for several decades, a closer look shows that this is not true. The commonly used tables (e.g., [1][2][3]) are by far not complete and sometimes even contain levels which are not existing. Thus, in some cases spectral lines, which are used for an analysis of the spectra of stars etc.…”

“…High-resolution spectrographs and photographic recording (on photo plates) enabled to classify most spectral lines of the chemical elements. The most famous collections of energy levels are the tables of C. Moore [1] and the NIST atomic database [2], and for the lanthanides [3]. Thus classical emission spectroscopy is the most important source of energy levels of atoms and their first ions.…”

Investigation of the Hyperfine Structure of Atomic Niobium (Nb I) Spectral Lines Based on the Lower Energy Levels at 22936, 23010, and 23048 cm<sup>-1</sup>

“…in refs. [22] [23]. Free Nb atoms were produced in a hollow cathode discharge, cooled by liquid nitrogen.…”

The Role of the Hyperfine Structure for the Determination of Improved Level Energies of Ta II, Pr II and La II

“…Either laser-induced fluorescence light or the change of the discharge impedance (optogalvanic detection) was observed. Details of the experimental arrangement can be found in various publications, e.g., [1][2][3].…”