When the energy of the X-ray irradiating the nucleus is of the same order of magnitude as the energy of the inner electrons of the nucleus, the inner electrons of the nucleus undergo a oscillatory transition after absorbing the radiation energy of the ray. A hole is left in the orbit, and the outer electron in the high-energy state jumps back to the hole in the low-energy state, releasing the excess energy in the form of X-rays. The X-rays generated are the X-ray fluorescence spectrum that represents the characteristics of each element. Wire. Its energy is equal to the energy difference between the inner shell electrons of the atom, that is, the specific electron interlayer transition energy of the atom. As long as the wavelengths of a series of X-ray fluorescence spectral lines are measured, the type of element can be determined. The intensity of the spectral lines is measured and compared with the standard sample to determine the content of the element, thus establishing the X-ray fluorescence spectrum.
Before 1895, X-rays produced by cathode ray tubes had been used in experiments for more than 30 years. Before the discovery of rays, there were constant complaints that photo negatives placed near cathode ray tubes were blurry or sensitive. . Such as Crookes in 1879, Goodspeed and others in 1890, but it was the German physicist "William Roentgen" who discovered X-rays
On November 8, 1895, German physicist Rontgen (1845-1923), in an experiment, wrapped the cathode ray discharge tube in thick black paper to prevent external light from disturbing the cathode rays. However, he noticed that there was a phosphor screen made of barium cyanide 1 meter away from the ray tube. This phosphor screen shone brightly with each discharge of the cathode ray tube. R?ntgen moved the fluorescent screen far away, and it still flashed; he also placed books, wooden boards, and aluminum sheets between the cathode ray discharge tube and the fluorescent screen, and the fluorescent screen still flashed; only a lead block or a thick iron plate was placed between them. , the flash will disappear. Obviously, the cathode ray tube emits a very penetrating ray, but it is not a cathode ray.
In the laboratory, Roentgen worked continuously for 6 weeks, carefully studying the relationship between this ray and the voltage applied to the discharge tube, studying the absorption characteristics of various objects for this ray, and the intensity distribution in all directions. He placed his palm between the cathode ray tube and the fluorescent screen, which clearly showed the bones of the palm. This kind of ray will also make the photographic film sensitive. He used the sensitive film to photograph his wife's slender hand with the ring. The result was that the photo was no longer poetic. The fingers on it looked like the phalanges of a skeleton with an irrelevant metal ring. . Later, he announced his research results to the outside world, and the incredible photo shocked the world.
Roentgen called this type of ray of unknown origin "X-ray" because in mathematics people are accustomed to using "X" to represent unknown numbers. Today, people know that "X-rays" are electromagnetic waves emitted by electrons from the cathode that are accelerated in an electric field and then suddenly decelerate and emit when they hit an object.
Using X-rays, people can see many tissue structures inside the body, discover accidental injuries to bones and metal shrapnel embedded in the body, thus helping doctors diagnose diseases. X-ray has great practical value. However, Roentgen did not apply for a technology patent for himself. He hoped that people all over the world could use it. Therefore, X-ray technology quickly spread to all parts of the world, effectively promoting medical progress.
Roentgen won the first Nobel Prize in Physics in 1901. However, he still lived a life of poverty in his later years and died lonely during the years of the Great Depression in Germany.