Ka doublet

Fig. 2 Aluminum x-ray Ka doublet, widened to partially compensate for energy analyzer broadening. Dotted curves, components solid curve, their sum.

In the present experiment, we took the aluminum Ka doublet components to be separated by 0.430 eV and to have a half-width of 0.35 eV each. The components were given a 2 1 intensity ratio and scaled to normalize the area under the combined peak. Figure 2 shows the resulting widened sx(x). 

The calibration source consists of a 20 keV electron gun and a series of metal targets (Mn, Cr, V, Ti) located on the opposite port to the spectrometer as indicated in Fig. 1. Calibration spectra are collected for a range of Ka and K/3 characteristic wavelengths (1.9A-2.8A) about the helium-like resonances of vanadium. Ka and Ka2 are well resolved in our system and so the Ka doublet provides two reference wavelengths at one detector location. This gives an absolute calibration of detector scale [17,18],... 

We often simply call Ka 1 and Ka2 radiations the Ka doublet. The K doublet is the most widely used monochromatic X-rays for diffraction work. Table 2.1 lists the commonly used Ka doublet, of which the wavelength is an average of Ka and Ka2. 

The wavelength of an unresolved Ka doublet is u of the wavelengths of its components, Aaj being gi is twice as strong. Thus the wavelength of the unrei... 

Fig. 1-5 Spectrum of Mo at 35 kV (schematic). Line widths not to scale. Resolved Ka. doublet is shown on an expanded wavelength scale at right.

What is the smallest value of 9 at which the Cr Ka doublet will be resolved in a 5.73-cm-diameter Debye camera Assume that the line width is 0.03 cm and that the separation must be twice the width for resolution. 

This equation results from the assumption that the diffraction line has the shape of an error curve [9.1].) Once B has been obtained from Eq. (9-1), it can be inserted into Eq. (3-13) to yield the particle size t. There are several other methods of finding B from Bf compared with Warren s method, they are somewhat more accurate and considerably more intricate. These other methods involve Fourier analysis of the diffraction lines from the unknown and from the standard, and considerable computation [G.30, G.39]. Even the approach involving Eq. (9-1) can be difficult if the line from the standard is a resolved Ka. doublet it is then simpler to use a Kfi line. The Fourier methods automatically take care of the existence of a doublet. 

The hardness curve and diffraction patterns of Fig. 9-3 illustrate these changes for an alpha brass, a solid solution of zinc in copper, containing 30 percent zinc by weight. The hardness remains practically constant, for an annealing period of one hour, until a temperature of 200°C is exceeded, and then decreases rapidly with increasing temperature, as shown in (a). The diffraction pattern in (b) exhibits the broad diffuse Debye lines produced by the cold-rolled, unannealed alloy. These lines become somewhat narrower for specimens annealed at 100° and 200°C, and the Ka. doublet becomes partially resolved at 250°C. At 250°, therefore, the re-... 

Best judged by noting whether or not the Ka doublet is resolved in back reflection. 

OET 99] OETZEL M., UEGER G., Laboratory X-ray powder diffraction a comparison of different geometries with special attention to the usage of the Cu Ka doublet , J. Appl. Cryst., vol. 32, p. 799-807,1999. 

Figure 2.3 X-Ray spectrum of molybdenum as a function of applied voltage (schematics). The spectral line widths are not to scale. The Ka doublet consists of unresolved Ka and Ka2 lines, with the former about twice as intense as the latter.

FIGURE 11.6 Typical X-ray map of the spherically-bent Si (220) crystal obtained with the Ka doublet of Cu and an asymmetric cut crystal to provide a highly parallel X-ray beam. 

---