R. C. M. Learner and A. P. Thorne, "Wavelength calibration of Fourier-transform emission spectra with applications to Fe i," J. Opt. Soc. Am. B 5, 2045-2059 (1988)
Absolute calibration requirements for Fourier-transform and classical grating spectrometers are compared. The methods and precautions needed for good Fourier-transform spectrometer calibration are illustrated by application to the iron hollow-cathode spectrum. Relative wave numbers in the Fe i spectrum can be determined with a precision of 5.8 × 10−9 (±0.00014 cm−1) for lines of good signal-to-noise ratio. The accuracy of calibration is limited by the inadequacy of available standards, by pressure shifts, and by effects of illumination, all of which are found at the 0.0005-cm−1 level. A preliminary list of 300 well-determined Fe i lines in the range 17 350–26 140 cm−1 (5760–3830 Å) is presented. The absolute accuracy is believed to be ±0.001 cm−1.
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The wave numbers in column 1 and the random errors (A) in column 6 are those of Norlén.11 Columns 2–5 and 7 are from this work. For definitions of these parameters see the footnotes to Table 3.
The statistical weight in column 8 is defined by C = 104/(A2 + B2).
Column 9 gives the simplified weight used in evaluating the standard error.
Columns 1, 2, 3, and 4 give the constants derived from the iterative fitting of a Voigt profile to each line. The lines listed are all those in spectrum N1 of Table 1 that (a) are Fe i, (b) have a signal-to-noise ratio greater than 100, and (c) are neither close blends nor self-reversed.
Intensity, in arbitrary units, based on the analytic integral of the fitted profile. The detectors were silicon photodiodes, and the observation range was defined using CuSO4 and GG400 filters.
Damping parameter: 1000 times the ratio of Lorentzian-to-Gaussian component half-widths. A low or zero damping parameter combined with a FWHM well above the Doppler value (4.7 × 10−6σ) indicates a line broadened by self-absorption.
The ratio of the peak intensity of the line to the rms value of the background noise for a window 30 cm−1 wide that includes the line. The noise level is not constant throughout the spectrum.
Calculated from the wave number by using Edlén’s dispersion formula. All observations were made in vacuum.
Wavelength in air from Ref. 6. Only the last three significant digits are quoted.
A percentage figure indicates a weak adjacent (Δσ < 2 × FWHM) line. Ne denotes a neon line. A question mark against the line at 22 382 cm−1 draws attention to the anomalous line-profile parameters. This line may be an accidental and unresolved blend.
Tables (3)
Table 1
Iron Hollow-Cathode Fourier-Transform Spectrometer Observations in the Region of 20 000 cm−1
The wave numbers in column 1 and the random errors (A) in column 6 are those of Norlén.11 Columns 2–5 and 7 are from this work. For definitions of these parameters see the footnotes to Table 3.
The statistical weight in column 8 is defined by C = 104/(A2 + B2).
Column 9 gives the simplified weight used in evaluating the standard error.
Columns 1, 2, 3, and 4 give the constants derived from the iterative fitting of a Voigt profile to each line. The lines listed are all those in spectrum N1 of Table 1 that (a) are Fe i, (b) have a signal-to-noise ratio greater than 100, and (c) are neither close blends nor self-reversed.
Intensity, in arbitrary units, based on the analytic integral of the fitted profile. The detectors were silicon photodiodes, and the observation range was defined using CuSO4 and GG400 filters.
Damping parameter: 1000 times the ratio of Lorentzian-to-Gaussian component half-widths. A low or zero damping parameter combined with a FWHM well above the Doppler value (4.7 × 10−6σ) indicates a line broadened by self-absorption.
The ratio of the peak intensity of the line to the rms value of the background noise for a window 30 cm−1 wide that includes the line. The noise level is not constant throughout the spectrum.
Calculated from the wave number by using Edlén’s dispersion formula. All observations were made in vacuum.
Wavelength in air from Ref. 6. Only the last three significant digits are quoted.
A percentage figure indicates a weak adjacent (Δσ < 2 × FWHM) line. Ne denotes a neon line. A question mark against the line at 22 382 cm−1 draws attention to the anomalous line-profile parameters. This line may be an accidental and unresolved blend.
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