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.
Highlights
Natural lanthanum (La), atomic number 57, is composed of two isotopes, a long-lived radioactive isotope 138La with a half-life of 1.05 × 1011 years [1] and a stable isotope 139La
At energies higher than 43,000 cm−1 we found a number of energy levels for which the observed lines show much higher values of the full width at half maximum (FWHM), and a practically pure Lorent
We present 16 new even La I energy levels in the energy range 40,300 to 46,100 cm−1
Summary
Natural lanthanum (La), atomic number 57, is composed of two isotopes, a long-lived radioactive isotope 138La (natural abundance 0.09%) with a half-life of 1.05 × 1011 years [1] and a stable isotope 139La (natural abundance 99.91%). These isotopes have nuclear spin quantum numbers 5 [2] and 7/2 [3], respectively. During evaluation of the recoded spectral lines, we noticed a strong dependency of the line width on the energy of the upper excited level, found while fitting the observed structures. E.g. −467(5) means −467 ± 5, 149.9(32) means 149.9 ± 3.2 and so on
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