EGAS41 - Swansea University

41 st EGAS CP 159 Gdańsk 2009
Discovery of new energy levels in praseodymium
I. Siddiqui 1 , S. Khan 1 , S. Tanweer Iqbal 1 , G.H. Guthöhrlein 1 , L. Windholz 1,∗
1 Instute of Experimental Physics, Graz University of Technology, Petersgasse 16,
A-8010 Graz, Austria
∗ Corresponding author: windholz@tugraz.at
One most important incentive in searching for new energy levels is the high energy level
density of an atom. Praseodymium is such a candidate. Our research group is extensively
involved in the investigation of the fine structure of praseodymium using the hyperfine
structure of the investigated transitions. Apart from some applications in other branches
of Physics, the hyperfine structure studies and complete mapping of energy levels in
praseodymium is of special significance for the theoretical understanding of the interactions
inside the atom.
We have discovered more than 600 new energy levels both in even and odd configurations
in last two years in a hollow cathode discharge using laser spectroscopy. Using
high resolution Fourier Transform Spectra (FTS) [1], one can very precisely tune the laser
wavelength to a hyperfine component to be investigated and then search for fluorescence
from excited levels. The excitation source is a ring-dye laser system pumped by a solid
state diode-pumped, frequency doubled Nd:Vanadate (Nd:YVO 4 ) Verdi V-18 laser system
or by a Krypton ion laser. The spectral region covered during these investigations
lie in the spectral range of Rhodamine 6G, Sulforhodamine B (Keton Red), DCM and
Coumarine Dyes.
As an example we discuss here the excitation of the lines 6092.35 Å and 6048.79 Å in
which we discovered a system of previously unknown lower and upper energy levels. The
signal-to-noise ratio for both the recorded structures was quite good and we were able to
fit both structures as transitions J = 15/2 to 15/2 and J = 17/2 to 15/2, respectively,
with high quality factor. From the determined magnetic interaction constants A we were
unable to indentify lower or upper levels in the data base of known levels. The fluorescence
observed for both transitions were the same and are 6081 Å, 5555 Å, 5387 Å, 5316 Å, 5032
Å. After detailed investigations we concluded that we were exciting the same unknown
upper level from two unknown lower levels. We then made an excitation of the line 6081.51
Å to the same unknown upper level as this line appeared as fluorescence line at the two
first excitations. This time from the determined magnetic interaction constants A we
were able to identify as lower level 17765.348 cm −1 , odd, 6.5 and 490(3) MHz. Using the
center of gravity excitation wavelength, the energy of upper level was determined to be
34204.135 cm −1 . It has even parity, J = 7.5 and A = 442(1) MHz. From the energy of
upper level we determined the data for the two lower levels as 17794.23 cm −1 , odd parity,
J = 7.5 and A = 221(1) MHz and 17676.482, odd parity, J = 8.5 and A = 857(1) MHz.
References
[1] B. Gamper, Diploma Thesis, Graz University of Technology, (2007)
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