A spherical mirror, autocollimating plane grating monochromator is described which is compact, stable, and exhibits spectral resolution which is better than 50 percent of the theoretical value. The spectrometer is 30 inches long and uses a 3-in. wide grating with 30,000 lines/inch. The optical system, although not in use in any modern spectrometer, was described by Ebert in 1889. The aberration corrective arrangement of the spherical mirror leaves only astigmatism as a serious aberration. The use of curved slits to remove this effect of astigmatism is described.
The mechanical-optical system is described in detail, and use of the instrument with a photomultiplier tube to record visible and ultraviolet emission spectra is described. Spectra are presented which demonstrate a second-order spectral resolution of 0.05A in the visible and ultraviolet region.
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