HOFSTEDTER (Hofstadter), Robert( American physicist, Nobel Prize in Physics, 1961)
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Biography HOFSTEDTER (Hofstadter), Robert
genus. February 5, 1915
American physicist Robert Hofstedter was born in New York. In the family of merchant Luis Hofstedtera and nee Henrietta Koenigsberg had four children, X. was the third son. Childhood years he spent in New York, the same was in high school and later enrolled at New York's City College, where he specialized in physics and mathematics. In 1935. H. received a bachelor's degree summa cum laude and the Kenyon Prize in physics and mathematics. All his life he retained thanks to one of the teachers college, who managed to convey to him his passion for the exact sciences - in fact originally the interests of X. lay in the field of philosophy. Scholarship Coffin from the company 'General Electric' allowed X. go to Princeton University. In 1938. he was awarded Master's degrees and Ph.D. in physics. Receiving a scholarship Procter, next year X. held at Princeton University, researching the photoconductivity of crystals. In 1940. He became a teacher of physics at Pennsylvania State University, and in 1941. - City College of New York. Becoming Fellow University of Pennsylvania, X. 1940 ... 1941. participated in the construction of a large Van de Graaff generator.
In 1942 ... 1943. H. worked at the National Bureau of Standards and contributed to the creation of photovoltaic remote detonators for anti-aircraft shells. From 1943 to 1946. he served as assistant principal physics of the company 'Norden Laboratories', organized by the creator of the famous bombsight Nordenia. After the war X. returned to academic life and in 1946. became an assistant professor at Princeton University. During this period his research focused on the crystals used as detectors of high energy particles and radiation. In 1948, Mr.. he developed a scintillation detector based on a crystal of sodium iodide salt, 'doped' a small amount of thallium. When faced with such a crystal of high-atomic particle, or photon (particle of light energy) there is a flash of light, whose intensity is proportional to the energy of particles or photons. By measuring the intensity of light, the experimenter is able to measure the energy and particles. This effect is the basis of the scintillation spectrometer - one of the basic measurement tools in the study of nuclear radiation.
In 1950, Mr.. H. was appointed associate professor of physics at Stanford University. Using a new electron accelerator Laboratory for High Energy Physics of the University, he began to study the structure of the nucleus. By that time, George P. Thompson, Clinton J. Davisson and others have shown that electrons have a wave nature. It was already known that with increasing energy electron wavelength decreases. Stanford accelerator allowed to disperse electrons to energies of 100 to 500 million. electron-volts, which corresponds to the wavelength of the electrons is less than the characteristic size of atomic nuclei. This meant that this accelerator could be used as a giant electron microscope, allows us to investigate the structure of atomic nucleus. In a collision with a nucleus of an electron accelerator at overclocked, is dismissed as a billiard ball. In some cases, the nucleus decays by emitting additional electrons and other particles. Investigating the wreckage of such collisions, X. hoping to get an idea about the structure of the nucleus.
X. measured the deflection of electrons, whose clashes with the nucleus is not accompanied by the emission of new particles. For this purpose he used two massive, weighing 250 tons, magnetic spectrometer - a device that allows to sort electrons by energy and angle of deviation from the original trajectory. With this equipment X. able to measure the magnitude and determine the shape of many nuclei. It turned out that they all have approximately the same average density. The volume of the nucleus is proportional to the total number of protons and neutrons. This means that in large heavy nuclei, these particles are not packed more densely than in the small pulmonary. Almost constant density of nuclei was equal to 150 million kg per m3. If a drop of water had a density, then it would weigh 2 million. tons.
Although X. and found that the average density of all nuclei is about the same, his experiments showed that the nucleus is not a simple sphere with a rigid shell. He has a soft 'hidden', the thickness of which is the same for all nuclei regardless of their size and amounts to about 2,4 бЇ 1013 cm
. After the Stanford accelerator after the renovation began to disperse the electrons to an energy of 1 billion electron-volts, X
. turned to the study of the internal structure of protons and neutrons - particles that make up the atomic nucleus. In 1956 ... 1957. he and his team determined the size and shape of the proton and the neutron. The researchers concluded that protons and neutrons are a variety of one particle, dubbed the nucleon. Although the proton and neutron have different electrical charge (positive in the proton and the neutron zero) in all processes related to the strong interaction, not yielding to disintegrate an atomic nucleus, they behave identically. Opening X. revealed the inadequacy of the then current theory of the nucleus and induced Yoshiro Nambu of the University of Chicago to reconsider its most important concepts. It was believed that the vector of interaction between the nucleons are pi-mesons - a particle with a mass of approximately half the mass of the proton. Nambu led theoretical arguments in favor of the more severe and short-carriers of the strong interaction. Predicted to them the particles were discovered in 1961
In 1961. H. was awarded the Nobel Prize in Physics "for fundamental studies of electron scattering in atomic nuclei and their related discoveries of the structure of the nucleons'. The second winner of the same year was Rudolf L. MцІssbauer. Introducing the new laureates, Ivar Waller of the Royal Swedish Academy of Sciences is particularly praised the distinctive features of the X. - 'Precision previously unattainable in high energy physics'. H. - Professor at Stanford University, where he continued his research on high energy physics. In 1942, Mr.. He joined the barque with Nancy Givon. In the couple had three children. Their son, Douglas became known as an expert on artificial intelligence. Feedback from colleagues, X. calm, quiet man. He loves listening to classical and jazz music, do photography, reading and skiing.
X. member of the National Academy of Sciences of the USA, Italian, American Physical Society and the London. In 1959, Mr.. in California, he was awarded the honorary title of "Scientist of Year '. In 1962. City College of New York snapped a medal in honor of the X. He was awarded honorary degrees from City College, and Carleton University of Padua.