Slit scattering

Mispositioned slits result in discrete slit scattering. Slit scattering is recognized by thin and intense streaks in horizontal and/or vertical direction that extend outward from the beam stop. Take out the sample or rotate it in order to make sure that the streaks are not resulting from an interaction of the beam with the sample. Horizontal streaks can be affected by moving horizontal slit edges. 

As a result slow variation of the adjustment is observed the intensity of the primary beam will abnormally increase or decrease, the parasitic scattering background will grow, slit scattering will change (cf. Sect. 4.2.3.7). It should be clear that changes of the primary beam intensity which are paralleled by respective changes of the synchrotron current are normal. 

Frequent reasons are that you (1) want to test what exposure will be needed, (2) have to check the slit scattering of the apparatus, (3) want to know if the beam comes through, (4) do not know if the sample is in the beam... 

Chart Speed Divergence Slit Receiving Slit Scatter Slit ... 

Usually, particle size has relatively little effect on Raman line shapes unless the particles are extremely small, less than 100 nm. For this reason, high-quality Raman spectra can be obtained from powders and from polycrystalline bulk specimens like ceramics and rocks by simply reflecting the laser beam from the specimen surface. Solid samples can be measured in the 90° scattering geometry by mounting a slab of the solid sample, or a pressed pellet of a powder sample so that the beam reflects from the surface but not into the entrance slit (Figure 3). 

Fig. 7-12. The curved-crystal spectrometer of Adler and Axelrod, showing a polished ore specimen in position. (1) Microscope stage (2) polished ore sample (3) crystal support block (4) Geiger counter and scatter slits. (Courtesy of Adler and Ayelrod and the U. S. Geological Survey.)...

A modern laser Raman spectrometer consists of four fundamental components a laser source, an optical system for focusing the laser beam on to the sample and for directing the Raman scattered light to the monochromator entrance slit, a double or triple monochromator to disperse the scattered light, and a photoelectric detection system to measure the intensity of the light passing through the monochromator exit slit (Fig. 7). 

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