X-Ray Wavelengths

Each spectrum is a continuum that extends over a wide range of wavelengths. The curves are left unfinished to call attention to the difficulty of working with long-wavelength x-rays. 

Because the mass of the sample is likely to be small, it is advisable to use long-wavelength x-rays to ensure measurable attenuation of the beam. 

Dry weight of living tissues, determined by long-wavelength x-ray absorptiometry, 297-300 Duane and Hunt, law of, 7 Dynodes, 56... 

Yamamoto, K., Takahashi, Y., Ohshima, K., Okamura, F.P. and Yukino, K. (1996) MEM analysis of electron-density distributions for silicon and diamond using short-wavelength X-rays (WKa, ), Acta Cryst., A52,606-613. 

X rays comprise that portion of the electromagnetic spectrum which lies between ultraviolet and gamma rays. The range of wavelengths is typically from about 0.01 to 100 A. Because of their very short wavelengths, X rays are powerful probes of atomic structure. 

R. Jenkins and J. A. Nicolosi, Long wavelength X-ray diffractometer, North American Phillips Corporation Patent Application, 1987. 

Angular-dispersive X-ray diffraction is used as a standard characterisation technique in the majority of solid-state laboratories. In this method, a constant-wavelength X-ray source is used. A detector sweeps a range of angles, and therefore Bragg reflections are separated by a spatial coordi-... 

Guss, J. M., et al. (1988). Phase determination by multiple-wavelength x-ray diffraction crystal structure of a basic blue copper protein from cucumbers. Science 241, 806-811. 

Fig. 1.7 Scattering of X-rays by successive crystal planes, with a spacing d apart Unless the difference In path length is a whole number of wavelengths, X-rays scattered by dffferent planes wW Interfere destructively.

The term smart material is now used for a rather wide variety of materials, some that have been known and used for many years and some that have been developed only recently. For example, phosphorescent and fluorescent materials are familiar and widely used materials that are sometimes defined as smart materials because they have the capacity to absorb electromagnetic radiation of short wavelengths (X-rays or ultraviolet rays, for example) and re-emit that radiation in the form of visible light. The difference between phosphorescence and fluorescence is that a phosphorescent material continues to emit light after radiation has ceased, while the emission of fluoresced light ends as soon as the source of radiation is removed. 

An electron beam is accelerated through a potential difference of 12 kV and falls onto a copper target. Calculate the shortest-wavelength X-rays that can be generated. [Answer 103 pm]... 

X-rays, electrons, and neutrons all have wavelike as well as particle nature, and each can be generated as a beam of a very limited energy (and therefore of a specific, or monochromatic, wavelength). X-rays and electrons are scattered when they hit electrons, and neutrons are scattered when they hit nuclei. If these electrons and nuclei are arranged in the three-dimensional regular array of a crystal lattice, scattering takes place only in specific directions that is, diffraction occurs. 

Region Wavelength X rays 0.1 j00nm Ultraviolet Tisifcle JOO- 400-400 nm 800 nm Infrared 800 nm 100 im Microwave JOO/itn-30 cm... 

Deformation density maps give some indications of the deformation from sphericity (or ellipticity) of the electrons of the atoms in the model as a result of chemical bonding or the existence of lone-pair electrons. They should, however, be interpreted with caution, especially with respect to the resolution of the electron-density map obtained from them. The maximum value of sin 0/A should be much higher than normally used, generally requiring short-wavelength X rays and low temperatures of measurement. 

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