Under the condition of laboratory control, the interaction between electrons and other particles can be used with particle detectors. Take a closer look. The characteristics of electrons, such as mass, spin and charge, can be measured and tested. Quadrupole ion trap and Pan Ning trap. Charged particles can be confined to a small area for a long time. In this way, scientists can accurately measure the properties of charged particles. For example, in one experiment, an electron was confined in the Pan Ning trap for 10 months.
In 1980, the experimental value of electron magnetic moment has been accurate to 1 1 digit. At that time, it was the most accurate of all measured physical constants. In February, 2008, a group of physics teams from Lund University took the video image of electron energy distribution for the first time. Scientists use very short flashes of light, called atto seconds. Pulse, the first to capture the actual movement of electrons.
In solid matter, the distribution of electrons can be visualized by angle-resolved photoelectron spectroscopy. This technology applies the photoelectric effect theory, irradiates high-energy radiation on the sample, and then measures the data of electron kinetic energy distribution and direction distribution of photoelectric emission. By analyzing these data carefully, we can infer the electronic structure of solid matter. American physicist robert millikan made a famous experiment in 1909, and accurately measured the charge of electrons. This experiment is called oil drop experiment. In this experiment, he used the coulomb force of electric field to balance the gravity felt by charged oil droplets. According to the strength of the electric field, he calculated the charge of the oil droplet. His instrument can measure the charge of oil droplets containing 1 ~ 150 ions with an error of less than 0.3%. He found that the charge of each oil droplet is a multiple of the same constant, so he deduced that this constant must be the charge of an electron.
Thomson and student John Thomson. Using electrolytic ionic gas to condense supersaturated water vapor, he obtained similar results by measuring the charge of charged water droplets. 19 1 1 year, Abram Effie. Using charged metal particles, the same results are obtained independently. He published this result in 19 1 1. Oil droplets are more stable than water droplets, and the evaporation rate of oil droplets is lower, which is more suitable for more lasting and accurate experiments.
At the beginning of the 20th century, experimenters found that fast-moving charged particles would condense supercooled and supersaturated water vapor into small fog beads on their paths. 19 1 1 year, Charlie Wilson applied this theory to design the cloud chamber instrument. The experimenter can shoot the trajectory of fast moving electrons with a camera. This is an important instrument for the early study of elementary particles. In different times, people have made various speculations about the existence of electrons in atoms.
The earliest atomic model is Tom Musun's plum pudding model. Published in 1904, Thomson thinks that electrons are evenly arranged in atoms, just like negatively charged plums in positively charged pudding. 1909, the famous Rutherford scattering experiment completely overthrew this model.
Rutherford designed the Rutherford model in 19 1 1 year according to his experimental results. In this model, most of the mass of atoms is concentrated in a small nucleus, and most atoms are in a vacuum. On the other hand, electrons revolve around the nucleus just as planets revolve around the sun. This model has a great influence on later generations. Until now, many high-tech organizations and units still use atomic images of electrons around the nucleus to express themselves.
Under the framework of classical mechanics, the planetary orbit model has a serious problem that cannot be explained: electrons move at an acceleration to generate electromagnetic waves, which will consume energy; Eventually, energy-exhausted electrons will hit the nucleus (just as energy-exhausted satellites will eventually enter the earth's atmosphere). 19 13 years, niels bohr put forward Bohr model. In this model, electrons move in a specific orbital region outside the nucleus. The farther away from the nucleus, the higher the orbital energy. When electrons jump to the orbital region closer to the nucleus, they will release energy in the form of photons. On the contrary, energy will be absorbed from the low-level orbital domain to the high-level orbital domain. Using these quantized orbital domains, Bohr correctly calculated the spectrum of hydrogen atoms. But Bohr model can not explain the relative intensity of spectral lines, nor can it calculate the spectra of more complex atoms. These problems have yet to be explained by quantum mechanics.
In 19 16, American physical chemist gilbert lewis successfully explained the interaction between atoms. He proposed that a pair of electrons between two atoms formed a valence bond. 1923, Walter Hayrett, Walter Hai Telei and Fritz London applied the theory of quantum mechanics to fully explain the reasons for the formation of electron pairs and chemical bonds. Irving langmuir introduced Louis' cubic atomic model in 19 19. It is proposed that all electrons are distributed in concentric (nearly concentric) spherical shells with the same thickness. He divided these spherical shells into several parts, and each part contained a pair of electrons. Using this model, he can explain the periodic chemical properties of each element in the periodic table.
1924, Austrian physicist Wolfgang Pao explained the shell structure of atoms with a set of parameters. The four parameters of this group determine the quantum state of electrons. Each quantum state can only be occupied by one electron. This rule which prohibits more than one electron from occupying the same quantum state is called Pauli exclusion principle. The first three parameters of this set of parameters are principal quantum number, angular quantum number and magnetic quantum number. The fourth parameter can have two different values. 1925, Dutch physicists Samuel Gosmitt, George Uhlenbeck and George Uhlenbeck proposed the physical mechanism represented by the fourth parameter. They think that besides the angular momentum of the moving orbital domain, electrons may also have internal angular momentum, called spin, which can be used to explain the mysterious spectral line splitting observed by high-resolution spectrometer in previous experiments. This phenomenon is called fine structure splitting. 1924, the French physicist Louis de Broglie put forward the De Broglie hypothesis in his doctoral thesis "Recherches sur la thé orie des quanta", which assumes that all substances have wave-particle duality like photons; That is to say, under appropriate conditions, substances such as electrons will show the properties of particles or fluctuations. If the physical experiment can show that particles move in the local position of space orbit with the evolution of time, then this experiment clearly shows the properties of particles. After the light wave passes through the double slit of the double slit experiment, the interference pattern will be produced on the detection barrier. This phenomenon undoubtedly distinguishes the essence of fluctuation. 1927, British physicist George Tang Musun used metal thin films, and American physicists Clinton Davidson and Lester Zimmer used nickel crystals to discover the interference effect of electrons respectively.
De Broglie's doctoral thesis gave Erwin Schr?dinger a great inspiration: since a particle fluctuates, there must be a wave equation that can completely describe the physical behavior of the particle. 1926, Schrodinger proposed the Schrodinger equation. This equation can describe the propagation mechanism of electron waves. It can't give the definite trajectory and position of electrons at any time qualitatively. But it can calculate the probability of an electron in a certain position, that is, the probability of finding an electron in a certain position. Schrodinger calculated the spectral line of hydrogen atom with his own equation, and got the same answer as predicted by Bohr model (see hydrogen atom for details). The wave concept of Schrodinger equation creates a new development platform for quantum mechanics. Furthermore, considering the spin of electrons and the interaction of several electrons, the Schrodinger equation can also give the electron configuration of electrons in other atoms with higher atomic order.
1928, paul dirac developed the Dirac equation. This formula can describe the physical behavior of relativistic electrons. Relativistic electrons are electrons moving near the speed of light. In order to explain the abnormal negative energy state problem encountered by the free electron solution of Dirac equation, Dirac proposed a vacuum model called Dirac Sea: vacuum is an infinite sea full of negative energy particles. Therefore, he predicted the existence of positrons (antimatter collocation of electrons) in the universe. 1932, carl anderson first confirmed the existence of positrons in cosmic ray experiments.
1947, willis lamb found in the experiment with Robert Retherford, a graduate student from Robert Rae, that some hydrogen atoms should not have degenerate energy differences, and even have very small energy differences. This phenomenon is called Lamb displacement. About the same time, polykarp kusch's assistant template and Henry Foley. In an experiment completed by * * *, it is found that the abnormal magnetic moment of electrons, that is, the magnetic moment of electrons is slightly larger than the value predicted by Dirac theory. In order to explain these phenomena, Asanaga Ichiro, Julian Schwinger and richard feynman founded quantum electrodynamics in AD1940s. In the first half of the twentieth century, the theory and equipment needed for the operation of particle accelerators have been developed. Physicists can begin to further study the properties of subatomic particles. 1942, Donald Kester Donald Kester. First, electromagnetic induction is successfully used to accelerate electrons to high energy. Under his leadership, the initial energy of the β accelerator reached 2.3MeV；; Later, the energy reached 300MeV. 1947, in the general electric laboratory, using a 70MeV electron synchrotron, physicists discovered synchrotron radiation, which is the radiation emitted by relativistic electrons due to acceleration when they move in a magnetic field.
1968, the first particle collider with a beam energy as high as 1.5GeV was named ADONE. At the Italian National Institute of Nuclear Physics. Start operation. This collider can accelerate electrons and positrons in opposite directions. Compared with the collision of stationary targets with electrons, this method can effectively double the collision energy From 1989 to 2000, the large electron-positron collider of the European Organization for Nuclear Research (CERN) located in the suburb of Geneva, Switzerland, can achieve collision energy as high as 209GeV. This collider has completed many experiments and made great contributions to testing and verifying the correctness of the standard model of particle physics. The mass of electrons appears in many basic laws in the subatomic field, but it is very difficult to measure them directly because of the extremely small mass of particles. A team of physicists overcame these challenges and obtained the most accurate electronic mass measurement to date.
An electron is bound in a hollow carbon atom core, and the synthesized atom is placed in a uniform electromagnetic field called Pan Ning ion trap. In the Pan Ning ion trap, atoms begin to oscillate at a stable frequency. The research team used microwaves to shoot trapped atoms, causing the electron spin to flip up and down. By comparing the frequency of atomic rotation with the frequency of spin-inversion microwave, researchers use quantum electrodynamics equations to obtain the mass of electrons.