EGAS41 - Swansea University

41 st EGAS CP 158 Gdańsk 2009
Rare low angular momenta energy levels in neutral
praseodymium
S. Khan 1 , S. Tanweer Iqbal 1 , I. Siddiqui 1 , L. Windholz 1,∗
1 Instute of Experimental Physics, Graz University of Technology, Petersgasse 16,
A-8010 Graz, Austria
∗ Corresponding author: windholz@tugraz.at
The interaction between electromagnetic multipole nuclear moments- magnetic moment,
electric quadrupole moment etc. and electromagnetic field produced at the nucleus by
electrons results in hyperfine splitting of fine levels. Nucleus has a compound structure
comprising protons and neutrons each with 1/2 intrinsic spin, giving the nucleus net
angular momentum with nuclear spin quantum number I. In analogy with LS coupling I
and J quantum numbers couple together to produce total angular momentum quantum
number F for the atom. For praseodymium the nuclear spin quantum number I is 2.5.
The number of hyperfine components are determined by 2I + 1 for J > I and by 2J + 1
for J < I.
In the investigation of neutral praseodymium atom in a hollow cathode discharge using
laser spectroscopy, we have discovered large number of previously unknown energy levels
with various angular momentum values. We present here energy levels with quite low
angular momenta, namely 1/2, 3/2 and 5/2. Of special significance are energy levels
with J = 0.5, since for these the resulting hyperfine splitting is due to the interaction
between magnetic field produced by the intrinsic electron spin S with L = 0 and the
nuclear magnetic moment. As an example we discuss the excitation of the line at 5756.49
Å. The S/N ratio for the recorded structure was quite reasonable and we were able to
fit the structure as a transition J = 1/2 to 3/2 with quite good quality factor. From
the determined magnetic interaction constants A, we were able to identify as lower level
13033.471 cm −1 , even parity, J = 1.5 and A = 905(4) MHz. Using the centre of gravity
excitation wavelength, the energy of the upper level was determined to be 30400.353 cm −1 ,
odd parity, J = 0.5 and A = 1885(5) MHz. Following is the recorded structure for the
line 5756.49 Å, observed at fluorescence line 5448 Å, the same structure is also observed
at fluorescence line 5141 Å.
1.0
0.9
Intensity (Arb.)
0.8
0.7
0.6
0.5
0.4
-5000 0 5000 10000 15000 20000 25000 30000 35000
Frequency MHz
218