Copper X rays

When an electron beam strikes a block of copper, x-rays with a frequency of 1.2 X lO1 Hz are emitted. How much energy is emitted at this wavelength by (a) an excited copper atom when it generates an x-ray photon (b) 2.00 mol of excited copper atoms (c) 2.00 g of copper atoms ... 

The first XRF spectrometers employed the wavelength dispersive methodology, which is schematically illustrated in the upper half of Fig. 7.17. The x-rays emanating from the source are passed through a suitable filter or filters to remove any undesired wavelengths, and collimated into a beam that is used to irradiate the sample. For instance, one typically uses a thin layer of elemental nickel to isolate the Ka lines of a copper x-ray source from contamination by the Kp lines, since the K-edge absorption of nickel will serve to pass the Kq, radiation but not the Kp radiation. 

The compositions of the basic acetates with varying copper acetate-copper hydroxide-water ratios may be determined by elemental analyses of carbon, hydrogen, oxygen and copper. X-ray and thermogravimetric analyses should provide further information on their compositions. 

XRD was used to identify crystalline mineral phases in the samples. A Rigaku-Geigerflex goniometer was used (copper X-ray source, 45 kV, 35 mA, 1575 W). Samples were run in triplicate and a fourth run was conducted after tungsten was added to one of the replicates as an external standard. The data were evaluated for possible crystalline phases using the PC-based search and match program MICRO-ID (Materials Data Corp., Livermore, CA). 

The x-ray radiation usually employed for protein crystallographic studies is derived from the bombardment of a copper target with high-voltage (50 kV) electrons, producing characteristic copper x-rays with A = 1.54 A. Figure 2 shows, in schematic fashion, the x-ray diffraction pattern from a protein crystal. Several features about this pattern bear explanation. First, as you can see, the diffraction pattern consists of a regular lattice of spots of different intensities. The spots are due to destructive interference of waves... 

X-ray diffraction data were obtained using Rigaku RAD-C with a copper X-ray tube in air atmosphere. X-ray absorption measurements of Cu K-edge were performed with laboratory EXAFS equipment (Technos EXAC-820). The X-ray source with a rotating Mo target and a LaBe filament was operated at 17 kV, 100 mA (EXAFS) and 20 kV 150 mA (XANES). The samples were pressed into wafers with methyl cellulose as a binder. The measurements were carried out in air atmosphere at room temperature. EXAFS Fourier transformations were carried out over the ranges of photoelectron wave vector, k, of 2.5 -10.0 A 1. 

It is suggestive that Ti02 appears to be more sensitive to x-irradiation than to gamma radiation, and more sensitive to x-irradiation than is Si02. A possible explanation, advanced earlier (2), is that the photoelectric ejection of K-electrons from titanium should be about ten times more efficient in the case of copper x-rays than the same process in silicon. K-electron ionization would be followed... 

The X-ray powder diffraction patterns (XRD) were obtained on a Rigaku D/Max 2500 diffractometer fitted with a fine-focus copper X-ray tube and operated at lOOkV and 40mA, respectively. The relative crystallization intensity (RCI) of CAS-1 was calculated following the procedures the five XRD diffraction peaks of the sample... 

X rays from a copper X-ray tube (A = 1.54 A) were diffracted at an angle of 14.22° by a crystal of silicon. Assuming first-order diffraction (n — 1 in the Bragg equation), what is the interplanar spacing in silicon ... 

The decrease for titania occurs at an unexpectedly low dose. The authors note that the copper X-rays should be highly effective for photoelectric ejection of K electrons from titanium, and that the multiply charged ions resulting from the subsequent Auger cascade may be very effective in reducing the surface area, perhaps simply because of the large energy liberation on neutralization. 

More detailed experiments with copper and nickel oxalates (184) confirmed the extensive decomposition under radiation, although the doses required to reach 80 to 90% metal appeared to be somewhat larger (perhaps by a factor of 2 to 3) than in the previous work (183). This could easily arise from differences in the techniques or in the materials. A preliminary irradiation insufficient to cause appreciable decomposition by itself (ca. 4 x 10 2 ev/gm) reduced the induction period and increased the rate of a subsequent thermal decomposition. There is considerable work on the effects of irradiation upon subsequent thermal decomposition of various solids, although not with catalyst preparation in mind (132h, 185-188). In the case of CaO, irradiation of the parent material, Ca(OH)2, did not affect the area of the oxide, although irradiation of the latter (with copper X-rays) decreased the specific surface for samples calcined (before irradiation) between 400 and 900°. 

Use a tungsten or copper X-ray source and a powder diffractometer. Load cmshed NaCl powder into the sample holder. Measure the diffraction pattern of the NaCl. Repeat with powdered KCl. Note the difference in spectra. Make mixtures by varying the amounts of NaCl and KCl. Can you distinguish the mixtures and the relative amounts of each component from the powder patterns ... 

PIXE analysis method has been applied primarily for the nondestructive elemental analysis of ancient copper coins. However, the high 3uelds of the copper X-rays and the high background which is created, cause serious difficulties in the accurate determination of zinc, nickel, iron, and in general for the elements with medium and low atomic numbers (Katsanos et al. 1986). For this reason, the complementary methods of proton-induced prompt y-ray emission and proton activation methods have been explored. PIXE has been used in... 

---