EGAS41 - Swansea University

41 st EGAS CP 4 Gdańsk 2009
Line strength measurements for selected Ne I spectral lines and
comparison with strengths of analogous transitions in Ar I
A. Bac̷lawski ∗ , J. Musielok
Institute of Physics, Opole University, ul. Oleska 48, 45-052 Opole, Poland
∗ Corresponding author: abac@uni.opole.pl,
Applying the emission spectroscopy method line strengths for several selected 3s - 3p and
3s - 4p transitions have been measured. A wall-stabilized high-current arc operated in
neon with some admixture of argon was applied for excitation of neon atoms. The electron
density of the arc plasma (N e = 8 · 10 15 cm −3 ) and temperature (T = 13 000 K) assured
partial local thermal equilibrium conditions among energy levels with principal quantum
number n ≥ 3. Details of the experimental setup, the data acquisition, and determination
of line strengths are described in a paper recently published by one of us [1].
The studied Ne I transitions occur between energy levels belonging to two groups of
terms with different atomic core configurations: 2s 2 2p 5 ( 2 P o 3/2 ) and 2s2 2p 5 ( 2 P o 1/2
). Each
set of measured line strengths: (i) 3s-3p; 3s-3p’; 3s’-3p; 3s’-3p’, and (ii) 3s-4p; 3s-4p’;
3s’-4p; 3s’-4p’, has been individually normalized to the strongest transition within each
set - 3s[3/2] o 2 - 3p[5/2] 3, and 3s[3/2] o 2 - 4p[5/2] 3, respectively.
These measured relative line strengths are compared with (relative) line strengths of
analogous transitions in Ar I. The corresponding line strengths have been taken from
NIST data base [2].
Regular behavior along the homologous sequence (Ne I - Ar I) is encountered in the
case of transitions involving levels belonging to the same parent term, i.e. without changing
the atomic core configuration. This regularity is observed for transitions originating
from upper levels with the principal quantum number n = 3 as well n = 4. Very large
discrepancies (between relative line strengths of neon and argon) are found in the case of
transitions occurring between levels belonging to different parent terms, i.e. for transitions
3s - 3p’, 3s - 4p’, 3s’ - 3p, and 3s’ - 4p.
This observation seems to be in accordance with line strength data reported for the
3p - 3d transition array (3p - 3d; 3p’ - 3d; 3p - 3d’; 3p’ - 3d’) in Ne I [1], where significant
departures from the J-file sum rule are found.
References
[1] A. Bac̷lawski, J. Phys. B: At. Mol. Phys. 41, 225701-2257013 (2008)
[2] NIST Atomic Spectra Database Lines - http://physics.nist.gov/PhysRefData/ASD/
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