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Accurate laboratory ultraviolet wavelengths for quasar absorption-line constraints on varying fundamental constants

Aldenius, Maria LU ; Johansson, Sveneric LU and Murphy, M. T. (2006) In Monthly Notices of the Royal Astronomical Society 370(1). p.444-452
Abstract
The most precise method of investigating possible space-time variations of the fine-structure constant, alpha equivalent to (1/hc)(e(2)/4 pi epsilon(0)), using high-redshift quasar absorption lines is the many-multiplet (MM) method. For reliable results this method requires very accurate relative laboratory wavelengths for a number of UV resonance transitions from several different ionic species. For this purpose laboratory wavelengths and wavenumbers of 23 UV lines from Mg I, Mg II, Ti II, Cr II, Mn II, Fe II and Zn II have been measured using high-resolution Fourier transform (FT) spectrometry. The spectra of the different ions (except for one Fe II line, one Mg I line and the Ti II lines) are all measured simultaneously in the same FT... (More)
The most precise method of investigating possible space-time variations of the fine-structure constant, alpha equivalent to (1/hc)(e(2)/4 pi epsilon(0)), using high-redshift quasar absorption lines is the many-multiplet (MM) method. For reliable results this method requires very accurate relative laboratory wavelengths for a number of UV resonance transitions from several different ionic species. For this purpose laboratory wavelengths and wavenumbers of 23 UV lines from Mg I, Mg II, Ti II, Cr II, Mn II, Fe II and Zn II have been measured using high-resolution Fourier transform (FT) spectrometry. The spectra of the different ions (except for one Fe II line, one Mg I line and the Ti II lines) are all measured simultaneously in the same FT spectrometry recording by using a composite hollow cathode as a light source. This decreases the relative uncertainties of all the wavelengths. In addition to any measurement uncertainty, the wavelength uncertainty is determined by that of the Ar II calibration lines, by possible pressure shifts and by illumination effects. The absolute wavenumbers have uncertainties of typically +/- 0.001 -+/- 0.002 cm(-1) (Delta lambda approximate to 0.06-0.1 m angstrom at 2500 angstrom), while the relative wavenumbers for strong, symmetric lines in the same spectral recording have uncertainties of +/- 0.0005 cm(-1) (Delta lambda approximate to 0.03 m angstrom at 2500 angstrom) or better, depending mostly on uncertainties in the line-fitting procedure. This high relative precision greatly reduces the potential for systematic effects in the MM method, while the new Ti II measurements now allow these transitions to be used in MM analyses. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
quasars : absorption lines, spectroscopic, techniques :, methods : laboratory, atomic data, line : profiles, ultraviolet : general
in
Monthly Notices of the Royal Astronomical Society
volume
370
issue
1
pages
444 - 452
publisher
Oxford University Press
external identifiers
  • wos:000239116800037
  • scopus:33746089121
ISSN
1365-2966
DOI
10.1111/j.1365-2966.2006.10491.x
language
English
LU publication?
yes
id
dd52c1e3-06b0-4b79-9793-ebc7e8620ac3 (old id 401303)
date added to LUP
2016-04-01 11:54:51
date last changed
2020-01-12 08:51:21
@article{dd52c1e3-06b0-4b79-9793-ebc7e8620ac3,
  abstract     = {The most precise method of investigating possible space-time variations of the fine-structure constant, alpha equivalent to (1/hc)(e(2)/4 pi epsilon(0)), using high-redshift quasar absorption lines is the many-multiplet (MM) method. For reliable results this method requires very accurate relative laboratory wavelengths for a number of UV resonance transitions from several different ionic species. For this purpose laboratory wavelengths and wavenumbers of 23 UV lines from Mg I, Mg II, Ti II, Cr II, Mn II, Fe II and Zn II have been measured using high-resolution Fourier transform (FT) spectrometry. The spectra of the different ions (except for one Fe II line, one Mg I line and the Ti II lines) are all measured simultaneously in the same FT spectrometry recording by using a composite hollow cathode as a light source. This decreases the relative uncertainties of all the wavelengths. In addition to any measurement uncertainty, the wavelength uncertainty is determined by that of the Ar II calibration lines, by possible pressure shifts and by illumination effects. The absolute wavenumbers have uncertainties of typically +/- 0.001 -+/- 0.002 cm(-1) (Delta lambda approximate to 0.06-0.1 m angstrom at 2500 angstrom), while the relative wavenumbers for strong, symmetric lines in the same spectral recording have uncertainties of +/- 0.0005 cm(-1) (Delta lambda approximate to 0.03 m angstrom at 2500 angstrom) or better, depending mostly on uncertainties in the line-fitting procedure. This high relative precision greatly reduces the potential for systematic effects in the MM method, while the new Ti II measurements now allow these transitions to be used in MM analyses.},
  author       = {Aldenius, Maria and Johansson, Sveneric and Murphy, M. T.},
  issn         = {1365-2966},
  language     = {eng},
  number       = {1},
  pages        = {444--452},
  publisher    = {Oxford University Press},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {Accurate laboratory ultraviolet wavelengths for quasar absorption-line constraints on varying fundamental constants},
  url          = {http://dx.doi.org/10.1111/j.1365-2966.2006.10491.x},
  doi          = {10.1111/j.1365-2966.2006.10491.x},
  volume       = {370},
  year         = {2006},
}