![]() This partly explained Röntgen’s confusion about the relationship between light and X-rays. In 1911, von Laue, a physics professor in Münich, determined that lines in diffraction gratings were not spaced closely enough to diffract X-rays. Light passing through a grating is dispersed – which means it is separated into different colors that go in different directions (Figure 12.3). The gratings consist of many parallel slits (or sometimes grooves), typically spaced between 0.0002 and 0.03 mm apart. Physicists routinely measured the wavelengths of colored light using finely spaced diffraction gratings. The diffraction of light was well understood at the time. 12.3 Diffraction gratings containing fine slits disperse light into different colors X-rays became inextricably involved with mineralogy when Max von Laue successfully used crystals as a tool in this search. Various physicists searched for an understanding of the nature of X-radiation. Because the radiation seemed to behave differently from light, he thought it a completely different phenomenon, calling it X-radiation. Röntgen deduced that electrons interacting with the walls of the tube produced a high-energy form of radiation, and he showed that the radiation could penetrate paper and even thin metals. By chance, he observed that a nearby piece of barium platinocyanide fluoresced when he turned on the tube. He was studying the relationship between matter and force as charged particles flowed from a heated filament in an evacuated glass tube. Röntgen taught and studied physics at the University of Würzburg in Germany. All this knowledge would have been unobtainable if Röntgen and his coworkers had not recognized the importance of some curious phenomena they observed while studying cathode ray tubes (early versions of television tubes) in 1895. We draw pictures, make enlarged models, and study the details of crystal structures of thousands of minerals. Today we accept without question the idea that atoms bond together in regular arrangements to make crystals. In less than two decades, scientists developed a firm theoretical basis for understanding how atoms are arranged in minerals. Mineralogists quickly discarded many hypotheses disproved by X-ray studies just as quickly, they developed and tested new ones. Wilhelm Conrad Röntgen’s discovery of X-rays in 1895 allowed mineralogists to proceed with their studies and eventually led to a greater understanding of crystal structures. Without a way to test hypotheses, development of an understanding of atomic arrangement and of bonding in crystals was stalled. Some ideas about crystal structure were generally accepted, while others were poorly understood and hotly debated. They hypothesized about atomic arrangements and the nature of crystal structures, but they lacked direct evidence. By the late nineteenth century, mineralogists knew that crystals had ordered and repetitive crystal structures. Scientists studied minerals for hundreds of years before the discovery of X-rays. Other important analytical techniques include X-ray fluorescence, atomic absorption, inductively coupled plasma mass spectrometry, ion microprobe, Mössbauer spectroscopy, visible and infrared spectroscopy, and Raman spectroscopy.ġ2.1 X-ray Diffraction 12.1.1 The Discovery of X-rays and Diffraction. ![]()
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