Scatter slit selection

As noted above, a scatter slit can be used to reduce the background noise before it reaches the detector. The aperture of the scatter slit should be selected to enable unobstructed passage of the monochromatic diffracted beam at any Bragg angle, see Figure 3.40. In this example, the scatter slit ScS is wide enough to transmit the beam without affecting its intensity. On the contrary, the scatter slit ScS is too narrow, and only a fraction of the diffracted intensity will reach the detector. 

Figure 3.40. Examples of proper (ScS) and improper (ScS ) selection of scatter slit aperture. DS - divergence slits, RS - receiving slits.

The besl isolation of radiant energy can he achieved with flame spectrometers that incorporate either a prism sir grating monochromator, those with prisms having variable gauged entrance and exii slits. Both these spectrometers provide a continuous selection of wavelengths with resolving power sufficient lo separate completely most of the easily excited emission lines, and afford freedom from scattered radiation sufficient lo minimize interferences. Fused silica or quartz optical components are necessary to permit measurements in Ihe ultraviolet portion of the spectrum below 350 nanometers Sec also Analysis (Chemical) Atomic Spectroscopy Photometers and Spectra Instruments. 

Once a single wavelength has been selected, the beam is collimated by passing it through a slit to remove wavelengths other than the desired one, before interaction with the sample and, finally, detection of the scattered X-rays. 

Fig. 3.5 Experimental arrangement for intracavity Raman spectroscopy with an argon laser CM, multiple reflection four-mirror system for efficient collection of scattered light LM, laser-resonator mirror DP, Dove prism, which turns the image of the horizontal interaction plane by 90° in order to match it to the vertical entrance slit S of the spectrograph FPE, Fabry-Perot etalon to enforce single-mode operation of the argon laser LP, Littrow prism for line selection [315]...

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