Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Accurate laboratory ultraviolet wavelengths for quasar absorption-line
  constraints on varying fundamental constants   The most precise method of investigating possible space-time variations of
the fine-structure constant, 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 MgI, MgII, TiII, CrII, MnII,
FeII and ZnII have been measured using high-resolution Fourier Transform (FT)
spectrometry. The spectra of the different ions (except for one FeII line, one
MgI line and the TiII 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 ArII calibration lines, by possible pressure shifts and by
illumination effects. The absolute wavenumbers have uncertainties of typically
0.001 to 0.002 cm^(-1) (0.06 to 0.1 mAA at 2500 AA), while the relative
wavenumbers for strong, symmetric lines in the same spectral recording have
uncertainties of 0.0005 cm^(-1) (0.03 mAA at 2500 AA) 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 TiII measurements now allow these transitions to be used
in MM analyses.

28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph