J/A+A/582/A43 Line lists of a nitrogen discharge (Boesch+, 2015)
Spectral line lists of a nitrogen gas discharge for wavelength calibration
in the range 4500-11000 cm-1.
Boesch A., Reiners A.
<Astron. Astrophys. 582, A43 (2015)>
=2015A&A...582A..43B 2015A&A...582A..43B (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: techniques: spectroscopic - methods: laboratory: molecular -
methods: data analysis
Abstract:
A discharge of nitrogen gas, as created in a microwave-induced plasma,
exhibits a very dense molecular emission line spectrum. Emission
spectra of this kind could serve as wavelength calibrators for
high-resolution astrophysical spectrographs in the near-infrared,
where only very few calibration sources are currently available.
The compilation of a spectral line list and the characterization of
line intensities and line density belong to the initial steps when
investigating the feasibility of potential wavelength calibration
sources. Although the molecular nitrogen spectrum was extensively
studied in the past, to our knowledge, no line list exists that covers
a continuous range of several thousand wavenumbers in the
near-infrared.
We recorded three high-resolution spectra of a nitrogen gas discharge
operated at different microwave powers. The nitrogen gas is kept
inside a sealed glass cell at a pressure of 2mbar. The emission lines
in the spectra were fitted by a superposition of Gaussian profiles to
determine their position, relative intensity, and width. The line
parameters were corrected for an absolute wavelength scale,
instrumental line broadening, and intensity modulation. Molecular and
atomic transitions of nitrogen were identified with available line
positions from the literature. We report line lists with more than
40000 emission lines in the spectral range 4500-11000cm-1
(0.9-2.2µm). The spectra exhibit emission lines over the complete
spectral range under investigation with about 350-1300 lines per
100cm-1. Depending on the microwave power, a fraction of 35%-55% of
all lines are blended. The total dynamic range of the detected lines
covers about four orders of magnitude.
Line density and peak intensities qualify the recorded discharge as a
useful wavelength calibrator, and the line list provides an empirical
reference for nitrogen spectra in the near-infrared.
Description:
The three FITS files (data_025.fit, data_050.fit and data_100.fit)
contain the spectra of the nitrogen discharge operated at a microwave
power of 25W, 50W, and 100W, respectively. The data format is a 1D
image of the flux values. The linear wavenumber scale can be
constructed from the XSTART and XEND values in the header.
The line lists (tab3_025.dat, tab3_050.dat and tab3_100.dat) contain
properties of the emission lines as determined from a simultaneous fit
with a superposition of Gaussian profiles. See Table 3 of the
associated paper for a more detailed column description.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tab3_025.dat 173 40408 Line list for discharge operated at 25W
tab3_050.dat 173 51776 Line list for discharge operated at 50W
tab3_100.dat 173 58274 Line list for discharge operated at 100W
list.dat 133 3 List of fits spectra
fits/* . 3 Individual fits files
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Byte-by-byte Description of file (#): tab3_025.dat tab3_050.dat tab3_100.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Designation of atom or molecule
13- 24 F12.6 cm-1 nu0c Line center, calibrated
26- 37 F12.6 cm-1 nu0 Line center
39- 53 F15.6 cm-1 e_nu0 Error on line center
55- 64 F10.6 --- Ic Line intensity, flat-field corrected
66- 75 F10.6 --- I Line intensity
77- 86 F10.6 --- e_I Error on line intensity
88- 97 F10.6 cm-1 sigma Width of Gaussian line profile
99-109 F11.6 cm-1 e_sigma Error on width of Gaussian line profile
111-120 F10.6 cm-1 FWHMc Full width at half maximum of line, corrected
122-131 F10.6 cm-1 FWHM Full width at half maximum of line
133-144 F12.6 cm-1 e_FWHM Error on full width at half maximum
146-155 F10.6 cm-1 Dist Distance of line center to reference line
157-161 A5 --- flags Indicates problems encountered during
analysis (1)
163-173 A11 --- Trans Transition as identified from literature
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Note (1): Flags as follows:
x = fit has failed or a fit parameter is at boundary condition.
y = fit residuals exceed at least 11 times (=intensity threshold+noise value)
the noise level and are larger than 5% of the peak intensity.
b = the neighboring line is closer than the sum of their FWHM and has more
than half of the line's peak intensity I (blend).
r = FWHM is narrower than the resolution set for the FTS.
f = σ(FWHM) is more than five time larger than the average error on
FWHM (for unidentified lines) or FWHMc scatters more than five times
from a linear trend for its species (for identified lines).
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 17 F17.12 cm-1 Xstar X value of the first data point
19- 34 F16.10 cm-1 Ystar X value of the last data point
36- 42 I7 --- Nx Number of data points
44- 47 I4 Kibyte Size Size of the file
49- 60 A12 --- FileName Name of the fits file in subdirectory fits
62-133 A72 --- Title Title of the file
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Acknowledgements:
Andreas Boesch, aboesch(at)astro.physik.uni-goettingen.de
(End) Andreas Boesch [Univ. Goettingen], Patricia Vannier [CDS] 23-Jul-2015