Multiply diffracted light in the Czerny-Turner spectrometer.
At certain small angles of the grating, any in-plane spectrometer will pass stray light that has been returned by the reflecting optics for a second diffraction. Paths of this source of stray light and its strueture have been calculated and confirmed experimentally.
Design criteria for a Raman spectrometer.
A Raman spectrochemical system has been developed based on laser radiation as the parent source. The high intensity of such radiation requires special considerations in the design of the spectrometer to reduce scattered primary radiation to better than one in part in 10(10), and these considerations are discussed. Coupling specimens of differing sizes and types to the incident radiation to optimize the intensity of Raman scattering necessitates differing approaches in optical design, and these are presented. Other design features discussed are the optics employed to collect and relay Raman radiation to the spectrometer, and the photon counting detector system. The performance of the system is typified by spectra obtained from specimens that present difficulties characteristic of Raman spectroscopy.
A Small Plane Grating Monochromator
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.