THE FUTURE OF THE DIFFRACTION GRATING IN HIGH RESOLUTION INFRARED.
Creators:Neill, Howard W.
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Publisher:Ohio State University
The recent application of Fourier transform spectrometry, principally by Pierre and Janine Connes, to the near infrared has placed a serious question as to the future role of the diffraction grating in applications where the very highest resolving power and the most precise wavelength measurements are required. Although its instrumentation and signal processing are somewhat more formidable than for the usual slit-grating devices, this form of transform spectrometry offers a resolving power of a few millikaysers, even for rather weak sources, and continuous wavelength measurement directly related to rare gas monoisotopic standards. Rather than kill high resolution grating spectrometry, these developments should serve notice to grating spectroscopists to adopt more sophisticated signal processing techniques. This is particularly true if the slit is replaced by the grille so that the luminosity is increased by some two orders of magnitude, although the Fellgett advantage cannot be generally invoked. In many cases it may be advantageous to use repetitive scanning so that successive waveforms from selected spectral intervals are stored and added coherently. Builders of grating instruments should also consider many techniques used by the Connes, as well as those used by builders of ruling engines and large telescopes, as far as bearing lubrication, fabrication of accurate gears, and servo controls are concerned. One particularly useful technique is that of a super-radiant source so that a meaningful apparatus function can be obtained and the spectrum improved by deconvolution using a digital computer. The extent to which some of these techniques have been applied to hot gas, atmospheric, and planetary sources will be discussed.
Author Institution: Naval Ordnance Laboratory
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