Hannover 2013 – scientific programme
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A: Fachverband Atomphysik
A 18: Precision spectroscopy of atoms and ions IV (with Q)
A 18.6: Talk
Tuesday, March 19, 2013, 15:30–15:45, B 305
The puzzle of the La line 6520.77 Å — •Laurentius Windholz1, Bettina Gamper1, Przemyslaw Glawocki2, and Jerzey Dembczynski2 — 1Institut für Experimentalphysik, Technische Universität Graz, Petersgasse 16, A-8010 Graz, Österreich — 2Chair of Quantum Engineering and Metrology, Faculty of Technical Physics, Poznań University of Technology, 60 965 Poznań, Poland
The strong La line 6520.770 Å is present in a Fourier transform spectrum available to us as a blend of two lines: a weak one at 6520.735 Å and a strong one at 6520.644 Å (signal to noise ratio of 250 in the Fourier transform spectrum). The latter we could not classify using all known energy levels of the La atom (La I) and its first ion (La II). It appears as a single broadened peak (FWHM 3.5 GHz), while the FWHM of a single hyperfine (hf) structure component is 1.2 GHz.
When setting the laser wavelength to 6520.65 Å, we observed a very strong optogalvanic (OG) modulation of the discharge current, and this did lead to the observation of more than 200 lines which showed laser-induced fluorescence (LIF) signals. Trying to use upper levels of LIF lines with opposite phase (compared to OG in-phase signals) as lower levels of the excited transition did lead to the assumption that a new upper level, 35449.041 cm-1, even, J=13/2, is participating. We applied Doppler-reduced intermodulated OG spectroscopy and were able to find the hf constants A of the involved levels. The angular momentum is 13/2 due to theoretical considerations. The new upper level shows only one combination with known lower levels, located in the infrared region (14908.421 Å).