EGAS41 - Swansea University

41 st EGAS CP 164 Gdańsk 2009
Investigation of fine and hyperfine structure of neutral La using
highly resolved Fourier transform spectra
L. Windholz 1,∗ , Y. Nighat 1,2 , M. Raith 1 ,
A. Jarmola 3 , M. Tamanis 3 , R. Ferber 3 , S. Kröger 4 , G. Basar 5
1 Inst. of Experimental Physics, Graz University of Technology,
Petersgasse 16, A-8010 Graz, Austria
2 National Institute of Lasers and Optronics, P.O. Nilore 44000, Islamabad, Pakistan
3 University of Latvia, Laser Centre, 19 Rainis Blvd., LV-1586 Riga, Latvia
4 Inst. f. Optik und Atomare Physik, Techn. Univ. Berlin,
Hardenbergstr. 36, D-10623 Berlin
5 Istanbul University, Physics Departement, TR-34134 Vezneciler, Istanbul
∗ Corresponding author: windholz@tugraz.at
Highly resolved Fourier transform spectra (resolution app. 0.03 cm −1 in the spectral range
3800 to 8800 Å have been recorded using a see-through La hollow cathode lamp as light
source, operated with Ar at 1 mbar and 60 mA dc current. The carefully done wavelength
calibration has been checked using standard Ar lines.
With help of these spectra, an improvement in the knowledge of the electronic structure
of the La atom (and also its first ion) can be reached:
• improvement of level energies
• classification of spectral lines by means of their characteristic hyperfine patterns
• determination of the hyperfine constants A and B, if unknown, of certain levels
• finding of new La spectral lines not implemented in commonly used spectral tables
• allowance for setting the excitation wavelength in laser spectroscopic investigations
to the highest peaks of a hyperfine pattern
Figure 1: Small part of the Fourier transform spectrum with La II and La I lines.
The new line 4921.596 Å could be classified as transition 36851.32 cm −1 , J=5/2,
even - 16538.39 cm −1 , J=7/2, odd. The new line at 4921.438 Å could be investigated
by means of laser excitation and detection of laser-induced fluorescence. It is a blend
between the transition 35117.70 cm −1 , J=5/2 even - 14804.08 cm −1 , J=5/2, odd and a
second transition, in which a new, up to now unknown La I energy level is involved.
This new level could be located with help of the recorded hyperfine pattern and excitation
and fluorescence wavelengths. Its data are 36556.76 cm −1 , J=9/2, even, A=472(5)
MHz , and the line is interpreted as transition to 16243.17 cm −1 , J=9/2, odd. This new
level explains also the new lines 4886.825 Å and 4994.019 Å with respect to wavelength
and hyperfine structure.
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