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Experimental oscillator strengths for forbidden lines in complex spectra

Hartman, Henrik LU ; Johansson, Sveneric LU ; Lundberg, Hans LU ; Lundin, P; Mannervik, S and Schef, P (2005) 8th International Colloquium on Atomic Spectra and Oscillator Strenghts, ASOS 8 In Physica Scripta T119. p.40-44
Abstract
In dilute astrophysical plasmas, such as planetary nebulae and H II regions, strong lines appear that only have weak, if any, correspondence to the spectrum of laboratory light sources. Some of these are parity forbidden lines, i.e. emission from long-lived metastable states that cannot decay via normal electric dipole (E1) routes but only via the slower M1 and E2 transitions. The long lifetime of the upper levels and their sensitivity to collisions make the lines good diagnostics of the emitting plasma, but then the transition probability, or A-value, of these lines must be known. We report on a technique to experimentally determine A-values for forbidden lines using the method of combining the lifetime of the upper level with the... (More)
In dilute astrophysical plasmas, such as planetary nebulae and H II regions, strong lines appear that only have weak, if any, correspondence to the spectrum of laboratory light sources. Some of these are parity forbidden lines, i.e. emission from long-lived metastable states that cannot decay via normal electric dipole (E1) routes but only via the slower M1 and E2 transitions. The long lifetime of the upper levels and their sensitivity to collisions make the lines good diagnostics of the emitting plasma, but then the transition probability, or A-value, of these lines must be known. We report on a technique to experimentally determine A-values for forbidden lines using the method of combining the lifetime of the upper level with the branching fractions for the different decay channels. The lifetime is measured using the laser probing technique (LPT) on a stored ion beam. Since these lines are rarely produced in laboratory plasmas, we use astrophysical spectra to determine the branching fractions (BF). The lifetime and the BF then give the A-value, which is one quantity needed for modeling the spectrum of the plasma emitting the forbidden lines. The present measurements are performed within the FERRUM project, an international collaboration producing and evaluating transition probabilities for iron group element lines of astrophysical importance [Johansson, P. I. S. et al., Physica Scripta T100, 71 (2002).] (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
keywords
Transition probability, Decay channels, Electric dipole, Branching fractions
in
Physica Scripta
volume
T119
pages
40 - 44
publisher
IOP Publishing
conference name
8th International Colloquium on Atomic Spectra and Oscillator Strenghts, ASOS 8
external identifiers
  • wos:000236906900008
  • scopus:33645659504
ISSN
0281-1847
DOI
10.1088/0031-8949/2005/T119/007
language
English
LU publication?
yes
id
bac8cf54-0bd4-452e-87c4-2066bb06d70d (old id 616374)
date added to LUP
2007-11-25 11:24:08
date last changed
2017-01-01 07:02:46
@inproceedings{bac8cf54-0bd4-452e-87c4-2066bb06d70d,
  abstract     = {In dilute astrophysical plasmas, such as planetary nebulae and H II regions, strong lines appear that only have weak, if any, correspondence to the spectrum of laboratory light sources. Some of these are parity forbidden lines, i.e. emission from long-lived metastable states that cannot decay via normal electric dipole (E1) routes but only via the slower M1 and E2 transitions. The long lifetime of the upper levels and their sensitivity to collisions make the lines good diagnostics of the emitting plasma, but then the transition probability, or A-value, of these lines must be known. We report on a technique to experimentally determine A-values for forbidden lines using the method of combining the lifetime of the upper level with the branching fractions for the different decay channels. The lifetime is measured using the laser probing technique (LPT) on a stored ion beam. Since these lines are rarely produced in laboratory plasmas, we use astrophysical spectra to determine the branching fractions (BF). The lifetime and the BF then give the A-value, which is one quantity needed for modeling the spectrum of the plasma emitting the forbidden lines. The present measurements are performed within the FERRUM project, an international collaboration producing and evaluating transition probabilities for iron group element lines of astrophysical importance [Johansson, P. I. S. et al., Physica Scripta T100, 71 (2002).]},
  author       = {Hartman, Henrik and Johansson, Sveneric and Lundberg, Hans and Lundin, P and Mannervik, S and Schef, P},
  booktitle    = {Physica Scripta},
  issn         = {0281-1847},
  keyword      = {Transition probability,Decay channels,Electric dipole,Branching fractions},
  language     = {eng},
  pages        = {40--44},
  publisher    = {IOP Publishing},
  title        = {Experimental oscillator strengths for forbidden lines in complex spectra},
  url          = {http://dx.doi.org/10.1088/0031-8949/2005/T119/007},
  volume       = {T119},
  year         = {2005},
}