|Born||February 5, 1915|
New York City
|Died||November 17, 1990 75) (aged|
|Alma mater|| City College of New York (BS)|
Princeton University (MS, PhD)
|Known for|| Electron scattering |
Sodium iodide scintillator
|Spouse(s)||Nancy (Givan) Hofstadter (1920–2007) (3 children including Douglas Hofstadter)|
|Awards|| Nobel Prize in Physics (1961)|
National Medal of Science (1986)
Dirac Medal (1987)
|Institutions|| Stanford University |
University of Pennsylvania
|Doctoral students||Carol Jo Crannell|
Robert Hofstadter (February 5, 1915 – November 17, 1990)was an American physicist. He was the joint winner of the 1961 Nobel Prize in Physics (together with Rudolf Mössbauer) "for his pioneering studies of electron scattering in atomic nuclei and for his consequent discoveries concerning the structure of nucleons".
Hofstadter was born into a Jewish family [ citation needed ]in New York City on February 5, 1915, to Polish immigrants, Louis Hofstadter, a salesman, and née Henrietta Koenigsberg. He attended elementary and high schools in New York City and entered City College of New York, graduating with a B.S. degree magna cum laude in 1935 at the age of 20, and was awarded the Kenyon Prize in Mathematics and Physics. He also received a Charles A. Coffin Foundation Fellowship from the General Electric Company, which enabled him to attend graduate school at Princeton University, where he earned his M.S. and Ph.D. degrees at the age of 23. His doctoral dissertation was titled "Infra-red absorption by light and heavy formic and acetic acids." He did his post-doctoral research at the University of Pennsylvania and was an assistant professor at Princeton before joining Stanford University. Hofstadter taught at Stanford from 1950 to 1985.
In 1942 he married Nancy Givan (1920–2007), a native of Baltimore.They had three children: Laura, Molly (who was disabled and not able to communicate), and Pulitzer Prize-winner Douglas Hofstadter.
In 1948 Hofstadter filed a patent on this for the detection of ionizing radiation by this crystal.These detectors are widely used for gamma ray detection to this day.
Robert Hofstadter coined the term fermi, symbol fm,in honor of the Italian physicist Enrico Fermi (1901–1954), one of the founders of nuclear physics, in Hofstadter's 1956 paper published in the Reviews of Modern Physics journal, "Electron Scattering and Nuclear Structure". The term is widely used by nuclear and particle physicists. When Hofstadter was awarded the 1961 Nobel Prize in Physics, it subsequently appears in the text of his 1961 Nobel Lecture, "The electron-scattering method and its application to the structure of nuclei and nucleons" (December 11, 1961).
In his last few years, Hofstadter became interested in astrophysics and applied his knowledge of scintillators to the design of the EGRET gamma-ray telescope of the Compton Gamma Ray Observatory named for fellow Nobel Laureate in Physics (1927), Arthur Holly Compton. Stanford University's Department of Physics credits Hofstadter with being "one of the principal scientists who developed the Compton Observatory."
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino; or, conversely a proton is converted into a neutron by the emission of a positron with a neutrino in so-called positron emission. Neither the beta particle nor its associated (anti-)neutrino exist within the nucleus prior to beta decay, but are created in the decay process. By this process, unstable atoms obtain a more stable ratio of protons to neutrons. The probability of a nuclide decaying due to beta and other forms of decay is determined by its nuclear binding energy. The binding energies of all existing nuclides form what is called the nuclear band or valley of stability. For either electron or positron emission to be energetically possible, the energy release or Q value must be positive.
Felix Bloch was a Swiss-American physicist and Nobel physics laureate who worked mainly in the U.S. He and Edward Mills Purcell were awarded the 1952 Nobel Prize for Physics for "their development of new ways and methods for nuclear magnetic precision measurements." In 1954–1955, he served for one year as the first Director-General of CERN. Felix Bloch made fundamental theoretical contributions to the understanding of ferromagnetism and electron behavior in crystal lattices. He is also considered one of the developers of nuclear magnetic resonance.
The neutron is a subatomic particle, symbol
, which has a neutral charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave similarly within the nucleus, and each has a mass of approximately one atomic mass unit, they are both referred to as nucleons. Their properties and interactions are described by nuclear physics.
Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter.
A timeline of atomic and subatomic physics.
Frederick Reines was an American physicist. He was awarded the 1995 Nobel Prize in Physics for his co-detection of the neutrino with Clyde Cowan in the neutrino experiment. He may be the only scientist in history "so intimately associated with the discovery of an elementary particle and the subsequent thorough investigation of its fundamental properties."
The femtometre symbol fm derived from the Danish and Norwegian word femten, "fifteen" (15), Ancient Greek: μέτρον, metrοn, "unit of measurement") is an SI unit of length equal to 10−15 metres, which means a quadrillionth of one. This distance can also be called a fermi and was so named in honour of Italian-American physicist Enrico Fermi, as it is a typical length-scale of nuclear physics.
Emilio Gino Segrè was an Italian-American physicist and Nobel laureate, who discovered the elements technetium and astatine, and the antiproton, a subatomic antiparticle, for which he was awarded the Nobel Prize in Physics in 1959 along with Owen Chamberlain.
Owen Chamberlain was an American physicist who shared with Emilio Segrè the Nobel Prize in Physics for the discovery of the antiproton, a sub-atomic antiparticle.
Burton Richter was an American physicist. He led the Stanford Linear Accelerator Center (SLAC) team which co-discovered the J/ψ meson in 1974, alongside the Brookhaven National Laboratory (BNL) team led by Samuel Ting for which they won Nobel Prize for Physics in 1976. This discovery was part of the November Revolution of particle physics. He was the SLAC director from 1984 to 1999.
Jerome Isaac Friedman is an American physicist. He is Institute Professor and Professor of Physics, Emeritus, at the Massachusetts Institute of Technology. He won the 1990 Nobel Prize in Physics along with Henry Kendall and Richard Taylor, for work showing an internal structure for protons later known to be quarks. Friedman sits on the Board of Sponsors of the Bulletin of the Atomic Scientists.
Henry Way Kendall was an American particle physicist who won the Nobel Prize in Physics in 1990 jointly with Jerome Isaac Friedman and Richard E. Taylor "for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for the development of the quark model in particle physics."
Electron scattering occurs when electrons are deviated from their original trajectory. This is due to the electrostatic forces within matter interaction or, if an external magnetic field is present, the electron may be deflected by the Lorentz force. This scattering typically happens with solids such as metals, semiconductors and insulators; and is a limiting factor in integrated circuits and transistors.
The neutron magnetic moment is the intrinsic magnetic dipole moment of the neutron, symbol μn. Protons and neutrons, both nucleons, comprise the nucleus of atoms, and both nucleons behave as small magnets whose strengths are measured by their magnetic moments. The neutron interacts with normal matter through either the nuclear force or its magnetic moment. The neutron's magnetic moment is exploited to probe the atomic structure of materials using scattering methods and to manipulate the properties of neutron beams in particle accelerators. The neutron was determined to have a magnetic moment by indirect methods in the mid 1930s. Luis Alvarez and Felix Bloch made the first accurate, direct measurement of the neutron's magnetic moment in 1940. The existence of the neutron's magnetic moment indicates the neutron is not an elementary particle, as for an elementary particle to have an intrinsic magnetic moment, it must have both spin and electric charge, and the neutron has spin 1/2 ħ, but no net charge. The existence of the neutron's magnetic moment was puzzling and defied a correct explanation until the quark model for particles was developed in the 1960s. The neutron is composed of three quarks, and the magnetic moments of these elementary particles combine to give the neutron its magnetic moment.
Understanding the structure of the atomic nucleus is one of the central challenges in nuclear physics.
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment. After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg. An atom is composed of a positively-charged nucleus, with a cloud of negatively-charged electrons surrounding it, bound together by electrostatic force. Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud. Protons and neutrons are bound together to form a nucleus by the nuclear force.
The EMC effect is the surprising observation that the cross section for deep inelastic scattering from an atomic nucleus is different from that of the same number of free protons and neutrons. From this observation, it can be inferred that the quark momentum distributions in nucleons bound inside nuclei are different from those of free nucleons. This effect was first observed in 1983 at CERN by the European Muon Collaboration, hence the name "EMC effect". It was unexpected, since the average binding energy of protons and neutrons inside nuclei is insignificant when compared to the energy transferred in deep inelastic scattering reactions that probe quark distributions. While over 1000 scientific papers have been written on the topic and numerous hypotheses have been proposed, no definitive explanation for the cause of the effect has been confirmed. Determining the origin of the EMC effect is one of the major unsolved problems in the field of nuclear physics.
Richard Edward Taylor,, was a Canadian physicist and Stanford University professor. He shared the 1990 Nobel Prize in Physics with Jerome Friedman and Henry Kendall "for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for the development of the quark model in particle physics."
The idea that matter consists of smaller particles and that there exists a limited number of sorts of primary, smallest particles in nature has existed in natural philosophy at least since the 6th century BC. Such ideas gained physical credibility beginning in the 19th century, but the concept of "elementary particle" underwent some changes in its meaning: notably, modern physics no longer deems elementary particles indestructible. Even elementary particles can decay or collide destructively; they can cease to exist and create (other) particles in result.
The discovery of the neutron and its properties was central to the extraordinary developments in atomic physics in the first half of the 20th century. Early in the century, Ernest Rutherford developed a crude model of the atom, based on the gold foil experiment of Hans Geiger and Ernest Marsden. In this model, atoms had their mass and positive electric charge concentrated in a very small nucleus. By 1920 chemical isotopes had been discovered, the atomic masses had been determined to be (approximately) integer multiples of the mass of the hydrogen atom, and the atomic number had been identified as the charge on the nucleus. Throughout the 1920s, the nucleus was viewed as composed of combinations of protons and electrons, the two elementary particles known at the time, but that model presented several experimental and theoretical contradictions.