Wavelength calibration of Fourier-transform emission spectra with applications to Fe i

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.