LiF(200), LiF(220), LiF(420)LiF crystal types exist in a variety of lattice planes (200, 220, 420, etc.). In the sequence (200) -- (220) -- (420), resolution increases and reflectivity decreases (Fig. 17).Fig. 17: Intensities of the crystals LiF(220) and LiF(420) in relation to LiF(200). (Intensity LiF(200) =1)LiF(200):A universally usable crystal for the element range atomic number 19 (K) onwards high reflectivity, highsensitivity.LiF(220):Lower reflectivity than LiF(200) but higher resolution can be used for the element range atomic number23 (V) onwards particularly suitable for better peak separation where peaks overlap.Examples of the application of the LiF(220) for reducing peak overlaps:Cr Ka1,2 - V Kb1Mn Ka1,2 - Cr Kb1U La1 - Rb Ka1,2LiF(420):One of the special crystals can be used for the element range atomic number 28 (Ni or Co Kb1) onwards best resolution but low reflectivity.Figure 17 shows a reflectivity of only 10% of that of LiF(200) for LiF(420) in the energy range around 10keV.PET:A universal crystal for the elements Al to Ti (K-peaks), Kr to Xe (L-peaks) and Hf to Bi (M-peaks).ATTENTIONThe PET is the crystal with the greatest heat-expansion coefficients, i.e. temperature fluctuations aremost noticeable here.Fundamental Principles Introduction to X-Ray Fluorescence (XRF)
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