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Delbrück Scattering
Delbrück scattering, the deflection of high-energy photons in the Coulomb field of nuclei as a consequence of vacuum polarization, was observed in 1975. The related process of the scattering of light by light, also a consequence of vacuum polarization, was not observed until 1998. In both cases, it is a process described by quantum electrodynamics. Image:Delbruck scattering.svg, The Feynman diagram of Delbrück scattering. The wavy line represents a photon and the double line an electron in the external field of a nucleus. Image:Delbruke scattering lowest.svg, The lowest order diagram has four vertices and consists of two incoming photons, which annihilate into a virtual electron-positron pair, which then annihilates into two real photons again. Discovery From 1932 to 1937, Max Delbrück worked in Berlin as an assistant to Lise Meitner, who was collaborating with Otto Hahn on the results of irradiating uranium with neutrons. During this period he wrote a few papers, one of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Max Delbrück
Max Ludwig Henning Delbrück (; September 4, 1906 – March 9, 1981) was a German–American biophysicist who participated in launching the molecular biology research program in the late 1930s. He stimulated physical science, physical scientists' interest into biology, especially as to basic research to physically explain genes, mysterious at the time. Formed in 1945 and led by Delbrück along with Salvador Luria and Alfred Hershey, the Phage Group made substantial headway unraveling important aspects of genetics. The three shared the 1969 Nobel Prize in Physiology or Medicine "for their discoveries concerning the replication mechanism and the genetic structure of viruses"."The Nobel Prize in Physiology or Medicine 1969" Nobel Media AB 2013, ''Nobelprize.org'', Web access November 6, 2013. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hans Bethe
Hans Albrecht Bethe (; July 2, 1906 – March 6, 2005) was a German-American theoretical physicist who made major contributions to nuclear physics, astrophysics, quantum electrodynamics, and solid-state physics, and who won the 1967 Nobel Prize in Physics for his work on the theory of stellar nucleosynthesis. For most of his career, Bethe was a professor at Cornell University.Available at www.JamesKeckCollectedWorks.or are the class notes taken by one of his students at Cornell from the graduate courses on Nuclear Physics and on Applications of Quantum Mechanics he taught in the spring of 1947. During World War II, he was head of the Theoretical Division at the secret Los Alamos National Laboratory, Los Alamos laboratory that developed the first atomic bombs. There he played a key role in calculating the critical mass of the weapons and developing the theory behind the implosion method used in both the Trinity test and the "Fat Man" weapon dropped on Nagasaki in August 1945. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giant Resonance
Giant resonance is a high-frequency collective excitation of atomic nuclei, as a property of many-body quantum systems. In the macroscopic interpretation of such an excitation in terms of an oscillation, the most prominent giant resonance is a collective oscillation of all protons against all neutrons in a nucleus. In 1947, G. C. Baldwin and G. S. Klaiber observed the giant dipole resonance (GDR) in photonuclear reactions, and in 1972 the giant quadrupole resonance (GQR) was discovered, and in 1977 the giant monopole resonance (GMR) was discovered in medium and heavy nuclei.Chomaz, section 2.2.2.1 Giant dipole resonance Giant dipole resonances may result in a number of de-excitation events, such as nuclear fission, emission of neutrons or gamma rays, or combinations of these. Giant dipole resonances can be caused by any mechanism that imparts enough energy to the nucleus. Classical causes are irradiation with gamma rays at energies from 7 to 40 MeV, which couple to nuclei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thomson Scattering
Thomson scattering is the elastic scattering of electromagnetic radiation by a free charged particle, as described by classical electromagnetism. It is the low-energy limit of Compton scattering: the particle's kinetic energy and photon frequency do not change as a result of the scattering. This limit is valid as long as the photon energy is much smaller than the mass energy of the particle: \nu\ll mc^2/h , or equivalently, if the wavelength of the light is much greater than the Compton wavelength of the particle (e.g., for electrons, longer wavelengths than hard x-rays). Description of the phenomenon In the low-energy limit, the electric field of the incident wave (photon) accelerates the charged particle, causing it, in turn, to emit radiation at the same frequency as the incident wave, and thus the wave is scattered. Thomson scattering is an important phenomenon in plasma physics and was first explained by the physicist J. J. Thomson. As long as the motion of the particle is no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Novosibirsk
Novosibirsk (, also ; rus, Новосиби́рск, p=nəvəsʲɪˈbʲirsk, a=ru-Новосибирск.ogg) is the largest city and administrative centre of Novosibirsk Oblast and Siberian Federal District in Russia. As of the Russian Census (2021), 2021 Census, it had a population of 1,633,595, making it the most populous city in Siberia and the list of cities and towns in Russia by population, third-most populous city in Russia. The city is located in southwestern Siberia, on the banks of the Ob River. Novosibirsk was founded in 1893 on the Ob River crossing point of the future Trans-Siberian Railway, where the Novosibirsk Rail Bridge was constructed. Originally named Novonikolayevsk ("New Nicholas") in honor of Emperor Nicholas II, the city rapidly grew into a major transport, commercial, and industrial hub. Novosibirsk was ravaged by the Russian Civil War but recovered during the early Soviet Union, Soviet period and gained its present name, Novosibirsk ("New Siberia"), i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Budker Institute Of Nuclear Physics
The Budker Institute of Nuclear Physics (BINP) is one of the major centres of advanced study of nuclear physics in Russia. It is located in the Siberian town Akademgorodok, on Academician Lavrentiev Avenue. The institute was founded by Gersh Budker in 1959. Following his death in 1977, the institute was renamed in honour of Academician Budker. Despite its name, the centre was not involved either with military atomic science or nuclear reactors instead, its concentration was on high-energy physics (particularly plasma physics) and particle physics. In 1961 the institute began building VEP-1,A. N. Skrinsly"Accelerator field development at Novosibirsk (history, status, prospects)" Particle Accelerator Conference, Proceedings of the 1995.V. N. Baier, "Forty years of acting electron-positron colliders"arXiv:hep-ph/0611201 [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rayleigh Scattering
Rayleigh scattering ( ), named after the 19th-century British physicist Lord Rayleigh (John William Strutt), is the predominantly elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scattering particle (normal dispersion regime), the amount of scattering is inversely proportional to the fourth power of the wavelength. Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency. The particle, therefore, becomes a small radiating dipole whose radiation we see as scattered light. The particles may be individual atoms or molecules; it can occur when light travels through transparent solids and liquids, but is most prominently seen in gases. Rayleigh scattering of sunlight in Earth's atmosphere causes d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Volt
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacuum. When used as a unit of energy, the numerical value of 1 eV in joules (symbol J) is equivalent to the numerical value of the charge of an electron in coulombs (symbol C). Under the 2019 redefinition of the SI base units, this sets 1 eV equal to the exact value Historically, the electronvolt was devised as a standard unit of measure through its usefulness in electrostatic particle accelerator sciences, because a particle with electric charge ''q'' gains an energy after passing through a voltage of ''V.'' Since ''q'' must be an integer multiple of the elementary charge ''e'' for any isolated particle, the gained energy in units of electronvolts conveniently equals that integer times the voltage. It is a common unit of energy within p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert R
Robert Lee Rayford (February 3, 1953 – May 15 1969), sometimes identified as Robert R. due to his age, was an American teenager from Missouri who has been suggested to represent the earliest confirmed case of HIV/AIDS in North America based on evidence which was published in 1988 in which the authors claimed that medical evidence indicated that he was "infected with a virus closely related or identical to human immunodeficiency virus type 1." Rayford died of pneumonia, but his other symptoms baffled the doctors who treated him. A study published in 1988 reported the detection of antibodies against HIV. Results of testing for HIV genetic material were reported once at a scientific conference in Australia in 1999; however, the data has never been published in a peer-reviewed medical or scientific journal. Background Robert Rayford was born on February 3, 1953, in St. Louis, Missouri to Constance Rayford (September 12, 1931 – April 3, 2011) and Joseph Benny Bell (March 24, 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Otto Hahn
Otto Hahn (; 8 March 1879 – 28 July 1968) was a German chemist who was a pioneer in the fields of radioactivity and radiochemistry. He is referred to as the father of nuclear chemistry and father of nuclear fission. Hahn and Lise Meitner discovered radioactive isotopes of radium, thorium, protactinium and uranium. He also discovered the phenomena of atomic recoil and nuclear isomerism, and pioneered rubidium–strontium dating. In 1938, Hahn, Lise Meitner and Fritz Strassmann discovered nuclear fission, for which Hahn received the 1944 Nobel Prize for Chemistry. Nuclear fission was the basis for nuclear reactors and nuclear weapons. A graduate of the University of Marburg, Hahn studied under Sir William Ramsay at University College London and at McGill University in Montreal under Ernest Rutherford, where he discovered several new radioactive isotopes. He returned to Germany in 1906; Emil Fischer placed a former woodworking shop in the basement of the Chemical Institute ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Two-photon Physics
Two-photon physics, also called gamma–gamma physics, is a branch of particle physics that describes the interactions between two photons. Normally, beams of light pass through each other unperturbed. Inside an optical material, and if the intensity of the beams is high enough, the beams may affect each other through a variety of non-linear effects. In pure vacuum, some weak scattering of light by light exists as well. Also, above some threshold of this center-of-mass energy of the system of the two photons, matter can be created. Astronomy Cosmological/intergalactic gamma rays Photon–photon interactions limit the spectrum of observed gamma-ray photons at moderate cosmological distances to a photon energy below around 20 GeV, that is, to a wavelength of greater than approximately . This limit reaches up to around 20 TeV at merely intergalactic distances. An analogy would be light traveling through a fog: At near distances you can see a light source more clearly t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lise Meitner
Elise Meitner ( , ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish physicist who was one of those responsible for the discovery of the element protactinium and nuclear fission. While working at the Kaiser Wilhelm Institute on radioactivity, she discovered the radioactive isotope protactinium-231 in 1917. In 1938, Meitner and her nephew, the physicist Otto Robert Frisch, discovered nuclear fission. She was praised by Albert Einstein as the "German Marie Curie". Completing her doctoral research in 1905, Meitner became the second woman from the University of Vienna to earn a doctorate in physics. She spent most of her scientific career in Berlin, Germany, where she was a physics professor and a department head at the Kaiser Wilhelm Institute; she was the first woman to become a full professor of physics in Germany. She lost these positions in the 1930s because of the anti-Jewish Nuremberg Laws of Nazi Germany, and in 1938 she fled to Sweden, where she lived for many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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