The Spectrometer Slit

Fixed slits or variable-width slits are available for spectrometers. The fixed slit widths are adjusted by the manufacturer. If fixed slits are used, the monochromator case has a mounting position in which interchangeable slits are mounted. Slits usually are constructed of stainless steel with the inner 

FIGURE 5-1. Bilateral variable slit mechanism. [Courtesy Jarrell-Ash Division, Fisher Scientific Co.] 

Slit mountings usually include arrangements to mount optical devices next to the slit. These devices may include neutral filters to limit exposure intensity, to limit the length of the spectral line, to view only a part of the total spectral line length, or to provide a gradation in line intensity over the length of the slit. 

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A mirror is placed past the focusing lens to reflect the beam vertically into the flame and parallel to the spectrometer slits. The fluorescence is collected by a 10 cm focal length lens and focused onto the entrance slit of a Spex 1800-11 spectrometer operated in second order. The spectral resolution is 0.1 nm. 

Figure 2-23 Schematic diagram of a rotating surface scanning device Li, rotating lens that focuses the laser beam on the surface of the sample and simultaneously collects the backscattered Raman light L2, focusing lens that focuses the Raman light on the spectrometer slit /, focal length of the lens. (Reproduced with permission from Ref. 48.)...

Figure 12.5. Two methods for directing light exiting the collection fiber into the spectrometer slit or aperture. Case A is simple and direct but does not allow adjustment of the numerical aperture of the fiber to match the // of the spectrometer. Case B is more common both because of greater flexibility and because it provides a parallel path region in which to place a BR filter.

In this work uniaxially oriented specimens of polyethylene terephthalate were studied, most of which were from the first series used in the work of Nobbs et al. described in Section 5.3.1. The Raman intensity measurements were made using a Coderg PHO spectrometer and a CRL 52A argon ion laser tuned to 488 nm. The tape samples were mounted parallel to the spectrometer slit. The partially focused laser beam was incident normally on them and the scattered light was collected in directions making approximately 180° with the incident light direction. The incident and scattered light polarisation vectors could be chosen parallel or... 

For high intensity work a spherical light collecting mirror can alternatively be used to reflect and focus a very large solid angle of the UV light to a position in front of the spectrometer slit where the gas beam is passing, see Fig.38. 

We have at present a maximum of 25 spherically bent quartz crystals (c )=30 mm) mounted for simultaneous focusing of the AlKa radiation onto the sample in front of the spectrometer slit. The result of the monochromatization is shown in Fig.40. It is fortuitous that at an almost identical Bragg angle ( > 78 ) as first order focusing of AlKa 2 occurs, second order focusing of AgLa, third order ScKg ... 

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