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Cluster Decay
Cluster decay, also named heavy particle radioactivity, heavy ion radioactivity or heavy cluster decay," is a rare type of nuclear decay in which an atomic nucleus emits a small "cluster" of neutrons and protons, more than in an alpha particle, but less than a typical binary fission fragment. Ternary fission into three fragments also produces products in the cluster size. Description The loss of protons from the parent nucleus changes it to the nucleus of a different element, the daughter, with a mass number ''Ad'' = ''A'' − ''Ae'' and atomic number ''Zd'' = ''Z'' − ''Ze'', where ''Ae'' = ''Ne'' + ''Ze''. For example: : → + According to "Ronen's golden rule" of cluster decay, the emitted nucleus tends to be one with a high binding energy per nucleon, and especially one with a magic number of nucleons. This type of rare decay mode was observed in radioisotopes that decay predominantly by alpha emission, and it occurs only in a small percentage of the decays for al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Neutron
The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nuclear fission in 1938, the first self-sustaining nuclear reactor (Chicago Pile-1, 1942) and the first nuclear weapon (Trinity (nuclear test), Trinity, 1945). Neutrons are found, together with a similar number of protons in the atomic nucleus, nuclei of atoms. Atoms of a chemical element that differ only in neutron number are called isotopes. Free neutrons are produced copiously in nuclear fission and nuclear fusion, fusion. They are a primary contributor to the nucleosynthesis of chemical elements within stars through fission, fusion, and neutron capture processes. Neutron stars, formed from massive collapsing stars, consist of neutrons at the density of atomic nuclei but a total mass more than the Sun. Neutron properties and interactions ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Alpha Decay
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). The parent nucleus transforms or "decays" into a daughter product, with a mass number that is reduced by four and an atomic number that is reduced by two. An alpha particle is identical to the nucleus of a helium-4 atom, which consists of two protons and two neutrons. It has a charge of and a mass of , and is represented as ^_\alpha. For example, uranium-238 undergoes alpha decay to form thorium-234. While alpha particles have a charge , this is not usually shown because a nuclear equation describes a nuclear reaction without considering the electrons – a convention that does not imply that the nuclei necessarily occur in neutral atoms. Alpha decay typically occurs in the heaviest nuclides. Theoretically, it can occur only in nuclei somewhat heavier than nickel (element 28), where the overall binding energy per nucleon is no longer a maximum a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Fission Isomer
A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy excited state levels (higher energy levels). "Metastable" describes nuclei whose excited states have half-lives of 10−9 seconds or longer, 100 to 1000 times longer than the half-lives of the excited nuclear states that decay with a "prompt" half life (ordinarily on the order of 10−12 seconds). Some references recommend seconds to distinguish the metastable half life from the normal "prompt" gamma-emission half-life. Occasionally the half-lives are far longer than this and can last minutes, hours, or years. For example, the nuclear isomer survives so long (at least years) that it has never been observed to decay spontaneously. The half-life of a nuclear isomer can even exceed that of the ground state of the same nuclide, as shown by as well as , , , , and multiple holmium isomers. Sometimes, the gamma decay from a metastable state is referred to a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Proton Emission
Proton emission (also known as proton radioactivity) is a rare type of radioactive decay in which a proton is ejected from a atomic nucleus, nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, in which case the process is known as beta-delayed proton emission, or can occur from the ground state (or a low-lying nuclear isomer, isomer) of very proton-rich nuclei, in which case the process is very similar to alpha decay. For a proton to escape a nucleus, the proton separation energy must be negative (Sp < 0)—the proton is therefore unbound, and quantum tunneling, tunnels out of the nucleus in a finite time. The rate of proton emission is governed by the nuclear, Coulomb, and centrifugal potentials of the nucleus, where centrifugal potential affects a large part of the rate of proton emission. The half-life of a nucleus with respect to proton emission is affected by the proton energy and its orbital angular momentum. Proton emiss ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Fritz Strassmann
Friedrich Wilhelm Strassmann (; 22 February 1902 – 22 April 1980) was a German chemist who, with Otto Hahn in December 1938, identified the element barium as a product of the bombardment of uranium with neutrons. Their observation was the key piece of evidence necessary to identify the previously unknown phenomenon of nuclear fission, as was subsequently recognized and published by Lise Meitner and Robert Frisch. In their second publication on nuclear fission in February 1939, Strassmann and Hahn predicted the existence and liberation of additional neutrons during the fission process, opening up the possibility of a nuclear chain reaction. Early life Friedrich Wilhelm (Fritz) Strassmann was born in Boppard, Germany, to Richard Strassmann and Julie Strassmann (née Bernsmann). He was the youngest of nine children. Growing up in Düsseldorf, he developed an interest in chemistry at a young age and conducted chemistry experiments in his parents' home. His family was of modes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Lise Meitner
Elise Lise Meitner ( ; ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish nuclear physicist who was instrumental in the discovery of nuclear fission. After completing her doctoral research in 1906, Meitner became the second woman from the University of Vienna to earn a doctorate in physics. She spent much of her scientific career in Berlin, where she was a physics professor and a department head at the Max Planck Institute for Chemistry, Kaiser Wilhelm Institute for Chemistry. She was the first woman to become a full professor of physics in Germany. She lost her positions in 1935 because of the anti-Jewish Nuremberg Laws of Nazi Germany, and the 1938 Anschluss resulted in the loss of her Austrian citizenship. On 13–14 July 1938, she fled to the Netherlands with the help of Dirk Coster. She lived in Stockholm for many years, ultimately becoming a Swedish citizen in 1949, but relocated to Britain in the 1950s to be with family members. In mid-1938, chemists Otto H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Otto Hahn
Otto Hahn (; 8 March 1879 – 28 July 1968) was a German chemist who was a pioneer in the field of radiochemistry. He is referred to as the father of nuclear chemistry and discoverer of nuclear fission, the science behind nuclear reactors and nuclear weapons. Hahn and Lise Meitner discovered isotopes of the radioactive elements isotopes of radium, radium, Isotopes of thorium, thorium, isotopes of protactinium, protactinium and isotopes of uranium, uranium. He also discovered the phenomena of atomic recoil and nuclear isomerism, and pioneered rubidium–strontium dating. In 1938, Hahn, Meitner and Fritz Strassmann Discovery of nuclear fission, discovered nuclear fission, for which Hahn alone was awarded the 1944 Nobel Prize in Chemistry. A graduate of the University of Marburg, which awarded him a doctorate in 1901, Hahn studied under Sir William Ramsay at University College London and at McGill University in Montreal under Ernest Rutherford, where he discovered several new radi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Georgy Flyorov
Georgii Nikolayevich Flyorov (also spelled Flerov, rus, Гео́ргий Никола́евич Флёров, p=gʲɪˈorgʲɪj nʲɪkɐˈlajɪvʲɪtɕ ˈflʲɵrəf; 2 March 1913 – 19 November 1990) was a Soviet physicist who is known for his discovery of spontaneous fission and his important contribution towards the crystallography and material science, for which, he was honored with many awards. In addition, he is also known for his letter directed to Joseph Stalin, during the midst of World War II, to start a program of nuclear weapons in the Soviet Union. In 2012, element 114 was named flerovium after the research laboratory at the Joint Institute for Nuclear Research bearing his name. Biography Flyorov was born on 2 March 1913 in Rostov-on-Don in Russia. His grandfather was a priest in the Russian Orthodox Church—his mother was Jewish. After finishing schooling in 1929, he was trained as a mechanic and later as an electrician, first working as a technician at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Konstantin Petrzhak
Konstantin Antonovich Petrzhak (alternatively Pietrzak; rus, Константи́н Анто́нович Пе́тржак, p=kənstɐnʲˈtʲin ɐnˈtonəvʲɪtɕ ˈpʲedʐək, ; 4 September 1907 – 10 October 1998), , was a Russian physicist of Polish origin, and a professor of physics at the Saint Petersburg State University. Receiving credit with Georgy Flyorov, a physicist, for the fundamental discovery of spontaneous fission of uranium in 1940, Petrzhak's career in physics was then spent mostly in the former Soviet program of nuclear weapons. Konstantin Petrzhak was among of Soviet pioneers in nuclear physics research. Biography Early and personal life Konstantin Petrzhak was born in Łuków, Poland in Russian Empire, on 4 September 1907. Other Russian documented sources noted his birthplace in Dombrovo in Kaliningrad with same birth date. There is very little information known about his early life and started working at the age of 12 (in 1919) as a painter at a glass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Spontaneous Fission
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic process. Spontaneous fission is a dominant decay mode for superheavy elements, with nuclear stability generally falling as nuclear mass increases. It thus forms a practical limit to heavy element nucleon number. Heavier nuclides may be created instantaneously by physical processes, both natural (via the r-process, ''r''-process) and artificial, though rapidly decay to more stable nuclides. As such, apart from minor decay branches in primordial radionuclides, spontaneous fission is not observed in nature. Observed fission half-lives range from 60 nanoseconds () to greater than the current age of the universe (). History Following the discovery of induced fission by Otto Hahn and Fritz Strassmann in 1938, Soviet physicists Georgy Flyorov and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Electromagnetic Force
In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interactions of atoms and molecules. Electromagnetism can be thought of as a combination of electrostatics and magnetism, which are distinct but closely intertwined phenomena. Electromagnetic forces occur between any two charged particles. Electric forces cause an attraction between particles with opposite charges and repulsion between particles with the same charge, while magnetism is an interaction that occurs between charged particles in relative motion. These two forces are described in terms of electromagnetic fields. Macroscopic charged objects are described in terms of Coulomb's law for electricity and Ampère's force law for magnetism; the Lorentz force describes microscopic charged particles. The electromagnetic force is responsible fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Weak Interaction
In nuclear physics and particle physics, the weak interaction, weak force or the weak nuclear force, is one of the four known fundamental interactions, with the others being electromagnetism, the strong interaction, and gravitation. It is the mechanism of interaction between subatomic particles that is responsible for the radioactive decay of atoms: The weak interaction participates in nuclear fission and nuclear fusion. The theory describing its behaviour and effects is sometimes called quantum flavordynamics (QFD); however, the term QFD is rarely used, because the weak force is better understood by Electroweak interaction, electroweak theory (EWT). The effective range of the weak force is limited to subatomic distances and is less than the diameter of a proton. Background The Standard Model of particle physics provides a uniform framework for understanding electromagnetic, weak, and strong interactions. An interaction occurs when two particles (typically, but not necess ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |