Issue |
A&A
Volume 462, Number 1, January IV 2007
|
|
---|---|---|
Page(s) | 1 - 6 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361:20066339 | |
Published online | 24 October 2006 |
Role of the He I and He II metastables in the resonance
2p 2P
B III level population
Faculty of Physics, University of Belgrade, PO Box 368, Belgrade, Serbia e-mail: steva@ff.bg.ac.yu
Received:
4
September
2006
Accepted:
13
October
2006
Aims.The aim of this work is to present atomic processes which lead to an extra population
of the B III resonance levels in helium plasma generating
intense radiation in the B III 206.578 nm and 206.723 nm lines.
Methods.The line profiles were recorded using a step-by-step (7.3 pm) technique which provides monitoring of the line shapes continually during the plasma decay and gives the possibility to compare line shapes at various times in the same plasma.
Results. On the basis of the line intensity decays of the doubly
ionized boron resonance spectral lines in laboratory nitrogen and helium plasmas, we have found the
existence of a permanent energy transfer from He I and He II
metastables to the 2p B III resonance levels. The shapes of the
mentioned lines are also observed. At electron temperatures of about 18 000 K and
electron densities about
m-3, the Stark
broadening was found as a main B III line broadening mechanism. The
measured Stark widths
are compared with the Doppler width
and with the splitting in the hyperfine structure
Our measured W data are found to be much higher than results
obtained by means of various theoretical approaches.
Conclusions. The He I and He II metastables over populate the B III resonance levels leading to populations higher than predicted by LTE model. Consequently, the emitted B III resonance lines are more intense than expected from LTE model. This fact can be of importance if B III resonance line intensities are used for abundance determination purposes in astrophysics. Similar behavior can be expected for some lines emitted by astrophysical interesting emitters: Al III, Si III, Sc III, Cr III, V III, Ti III, Fe III, Co III, Ni III, Ga III, Zr III, Y III, Nb III, In III, Sn III, Sb III, Au III, Pb III and Bi III in hot and dense helium plasmas.
Key words: plasmas / atomic data / atomic processes / line: profiles / radiation mechanisms: non-thermal
© ESO, 2007
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.