Abstract
The strong La line 6520.644 ? is present in a Fourier Transform Spectrum (signal to noise ratio of 240), but its wavelength in commonly used tables (e.g. [1]) is given as 6520.770 ?, while in [2] the wavelength is given as 6520.74 ?, unclassified, with the remark “h” (hazy). The line could not be classified using known energy levels of the La atom (La I) and its first ion (La II). It appears as a single broadened peak. By a combination of laser optogalvanic spectroscopy, laser-induced fluorescence and Doppler-reduced saturation spectroscopy we could introduce a new even parity La I energy level, 35449.041 cm -1, J = 13/2, with hyperfine (hf) constants A = ?8.0(5) MHz, B = 10(10) MHz. For a second, up to now unknown neighbouring La I line (wavelength 6519.869 ?) we introduced another even parity energy level involved in the formation of the line, 41207.994 cm -1, J = 13/2, A = 91.6(5) MHz, B = 170(50) MHz. We tried also to explain why in old tables the wavelength given was so different.
Highlights
Our group is performing systematic investigations of the hyperfine resolved spectrum of the La atom, more precisely on the stable isotope La139
Its energy levels show nice hyperfine splitting which can be used as finger print for the corresponding level
In order to gain information on up to now unknown energy levels, we investigate spectral lines which can not be explained as transitions between already known energy levels
Summary
Our group is performing systematic investigations of the hyperfine (hf) resolved spectrum of the La atom (atomic number 57), more precisely on the stable isotope La139 (natural abundance 99.91%). This isotope has nuclear spin quantum number 7/2 [3], a magnetic dipole moment μI = 2.7830455(9) μN and a small electric. Since by far not all theoretically expected levels are experimentally known, experimental effort to find the missing levels is necessary. In order to gain information on up to now unknown energy levels, we investigate spectral lines which can not be explained as transitions between already known energy levels.
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