Clinton Davisson

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Clinton Joseph Davisson
Clinton Davisson.jpg
Davisson
Born(1881-10-22)October 22, 1881
DiedFebruary 1, 1958(1958-02-01) (aged 76)
NationalityUnited States
Alma mater University of Chicago (B.S., 1908)
Princeton University (Ph.D, 1911)
Known for Electron diffraction
Spouse(s)Charlotte Davisson
Awards Comstock Prize in Physics (1928) [1]
Elliott Cresson Medal (1931)
Hughes Medal (1935)
Nobel Prize in Physics (1937)
Scientific career
Fields Physics
Institutions Princeton University
Carnegie Institute of Technology
Bell Labs
Doctoral advisor Owen Richardson
InfluencedJoseph A. Becker
Mervin Kelly
William Shockley

Clinton Joseph Davisson (October 22, 1881 – February 1, 1958) was an American physicist who won the 1937 Nobel Prize in Physics for his discovery of electron diffraction in the famous Davisson–Germer experiment. Davisson shared the Nobel Prize with George Paget Thomson, who independently discovered electron diffraction at about the same time as Davisson.

Contents

Early life and education

Davisson was born in Bloomington, Illinois. He graduated from Bloomington High School in 1902, and entered the University of Chicago on scholarship. Upon the recommendation of Robert A. Millikan, in 1905 Davisson was hired by Princeton University as Instructor of Physics. He completed the requirements for his B.S. degree from Chicago in 1908, mainly by working in the summers. While teaching at Princeton, he did doctoral thesis research with Owen Richardson. He received his Ph.D. in physics from Princeton in 1911; in the same year he married Richardson's sister, Charlotte. [2] [3]

Scientific career

Davisson was then appointed as an assistant professor at the Carnegie Institute of Technology. In 1917, he took a leave from the Carnegie Institute to do war-related research with the Engineering Department of the Western Electric Company (later Bell Telephone Laboratories). At the end of the war, Davisson accepted a permanent position at Western Electric after receiving assurances of his freedom there to do basic research. He had found that his teaching responsibilities at the Carnegie Institute largely precluded him from doing research. [2] Davisson remained at Western Electric (and Bell Telephone) until his formal retirement in 1946. He then accepted a research professor appointment at the University of Virginia that continued until his second retirement in 1954. [2]

Electron Diffraction and the Davisson–Germer Experiment

Diffraction is a characteristic effect when a wave is incident upon an aperture or a grating, and is closely associated with the meaning of wave motion itself. In the 19th Century, diffraction was well established for light and for ripples on the surfaces of fluids. In 1927, while working for Bell Labs, Davisson and Lester Germer performed an experiment showing that electrons were diffracted at the surface of a crystal of nickel. This celebrated Davisson–Germer experiment confirmed the de Broglie hypothesis that particles of matter have a wave-like nature, which is a central tenet of quantum mechanics. In particular, their observation of diffraction allowed the first measurement of a wavelength for electrons. The measured wavelength agreed well with de Broglie's equation , where is Planck's constant and is the electron's momentum. [4]

Personal life

While doing his graduate work at Princeton, Davisson met his wife and life companion Charlotte Sara Richardson, who was visiting her brother, Professor Richardson. [5] Richardson is the sister-in-law of Oswald Veblen, a prominent mathematician. [6] Clinton and Charlotte Davisson (d.1984) had one child, the American physicist Richard Davisson.

Death and legacy

Davisson died on February 1, 1958, at the age of 76. [7] [8]

An impact crater on the far side of the moon was named after Davisson in 1970 by the IAU. [9]

See also

Related Research Articles

Diffraction Phenomenon of the motion of waves

Diffraction refers to various phenomena that occur when a wave encounters an obstacle or opening. It is defined as the bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wave. Italian scientist Francesco Maria Grimaldi coined the word diffraction and was the first to record accurate observations of the phenomenon in 1660.

Double-slit experiment Physics experiment, showing light can be modelled by both waves and particles

In modern physics, the double-slit experiment is a demonstration that light and matter can display characteristics of both classically defined waves and particles; moreover, it displays the fundamentally probabilistic nature of quantum mechanical phenomena. This type of experiment was first performed, using light, by Thomas Young in 1801, as a demonstration of the wave behavior of light. At that time it was thought that light consisted of either waves or particles. With the beginning of modern physics, about a hundred years later, it was realized that light could in fact show behavior characteristic of both waves and particles. In 1927, Davisson and Germer demonstrated that electrons show the same behavior, which was later extended to atoms and molecules. Thomas Young's experiment with light was part of classical physics long before the development of quantum mechanics and the concept of wave-particle duality. He believed it demonstrated that the wave theory of light was correct, and his experiment is sometimes referred to as Young's experiment or Young's slits.

Wavelength Spatial period of the wave—the distance over which the waves shape repeats, and thus the inverse of the spatial frequency

In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter lambda (λ). The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids.

Wave–particle duality is the concept in quantum mechanics that every particle or quantum entity may be described as either a particle or a wave. It expresses the inability of the classical concepts "particle" or "wave" to fully describe the behaviour of quantum-scale objects. As Albert Einstein wrote:

It seems as though we must use sometimes the one theory and sometimes the other, while at times we may use either. We are faced with a new kind of difficulty. We have two contradictory pictures of reality; separately neither of them fully explains the phenomena of light, but together they do.

Arago spot Bright point that appears at the center of a circular objects shadow due to Fresnel diffraction

In optics, the Arago spot, Poisson spot, or Fresnel spot is a bright point that appears at the center of a circular object's shadow due to Fresnel diffraction. This spot played an important role in the discovery of the wave nature of light and is a common way to demonstrate that light behaves as a wave.

Louis de Broglie

Louis Victor Pierre Raymond, 7th Duc de Broglie was a French physicist and aristocrat who made groundbreaking contributions to quantum theory. In his 1924 PhD thesis, he postulated the wave nature of electrons and suggested that all matter has wave properties. This concept is known as the de Broglie hypothesis, an example of wave–particle duality, and forms a central part of the theory of quantum mechanics.

Matter waves are a central part of the theory of quantum mechanics, being an example of wave–particle duality. All matter exhibits wave-like behavior. For example, a beam of electrons can be diffracted just like a beam of light or a water wave. In most cases, however, the wavelength is too small to have a practical impact on day-to-day activities.

Electron diffraction refers to the wave nature of electrons. However, from a technical or practical point of view, it may be regarded as a technique used to study matter by firing electrons at a sample and observing the resulting interference pattern. This phenomenon is commonly known as wave–particle duality, which states that a particle of matter can be described as a wave. For this reason, an electron can be regarded as a wave much like sound or water waves. This technique is similar to X-ray and neutron diffraction.

Edward Victor Appleton English physicist and Nobel Prize recipient (1892–1965)

Sir Edward Victor Appleton was an English physicist, Nobel Prize winner (1947) and pioneer in radiophysics. He studied, and was also employed as a lab technician, at Bradford College from 1909 to 1911.

In physics, Bragg's law, Wulff–Bragg's condition or Laue-Bragg interference, a special case of Laue diffraction, gives the angles for coherent scattering of waves from a crystal lattice. It encompasses the superposition of wave fronts scattered by lattice planes, leading to a strict relation between wavelength and scattering angle, or else to the wavevector transfer with respect to the crystal lattice. Such law had initially been formulated for X-rays upon crystals but is moreover relevant for all kind of quantum beams, such as neutron and electron waves on atomic spacing, as well as for visual light on artificial periodic micro-scale lattices.

Arthur Compton American physicist

Arthur Holly Compton was an American physicist who won the Nobel Prize in Physics in 1927 for his 1923 discovery of the Compton effect, which demonstrated the particle nature of electromagnetic radiation. It was a sensational discovery at the time: the wave nature of light had been well-demonstrated, but the idea that light had both wave and particle properties was not easily accepted. He is also known for his leadership over the Metallurgical Laboratory at the University of Chicago during the Manhattan Project, and served as chancellor of Washington University in St. Louis from 1945 to 1953.

Owen Willans Richardson

Sir Owen Willans Richardson, FRS was a British physicist who won the Nobel Prize in Physics in 1928 for his work on thermionic emission, which led to Richardson's law.

George Paget Thomson British physicist and Nobel laureate in physics

Sir George Paget Thomson, FRS was a British physicist and Nobel laureate in physics recognized for his discovery of the wave properties of the electron by electron diffraction.

Davisson (crater)

Davisson is a lunar impact crater that is located on the far side of the Moon from the Earth. This crater lies across the eastern rim of the huge walled plain Leibnitz, and the rim and outer rampart intrudes into the interior floor of Leibnitz. To the east-northeast of Davisson is the walled plain Oppenheimer, a formation only somewhat smaller than Leibnitz.

The Davisson–Germer experiment was a 1923-27 experiment by Clinton Davisson and Lester Germer at Western Electric, in which electrons, scattered by the surface of a crystal of nickel metal, displayed a diffraction pattern. This confirmed the hypothesis, advanced by Louis de Broglie in 1924, of wave-particle duality, and was an experimental milestone in the creation of quantum mechanics.

Lester Germer

Lester Halbert Germer was an American physicist. With Clinton Davisson, he proved the wave-particle duality of matter in the Davisson–Germer experiment, which was important to the development of the electron microscope. These studies supported the theoretical work of De Broglie. He also studied thermionics, erosion of metals, and contact physics. He was awarded the Elliott Cresson Medal in 1931.

Quantum mechanics is the study of very small things. It explains the behavior of matter and its interactions with energy on the scale of atomic and subatomic particles. By contrast, classical physics explains matter and energy only on a scale familiar to human experience, including the behavior of astronomical bodies such as the Moon. Classical physics is still used in much of modern science and technology. However, towards the end of the 19th century, scientists discovered phenomena in both the large (macro) and the small (micro) worlds that classical physics could not explain. The desire to resolve inconsistencies between observed phenomena and classical theory led to two major revolutions in physics that created a shift in the original scientific paradigm: the theory of relativity and the development of quantum mechanics. This article describes how physicists discovered the limitations of classical physics and developed the main concepts of the quantum theory that replaced it in the early decades of the 20th century. It describes these concepts in roughly the order in which they were first discovered. For a more complete history of the subject, see History of quantum mechanics.

Electron scattering Deviation of electrons from their original trajectories

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.

Low-energy electron diffraction A technique for the determination of the surface structure of single-crystalline materials

Low-energy electron diffraction (LEED) is a technique for the determination of the surface structure of single-crystalline materials by bombardment with a collimated beam of low-energy electrons (30–200 eV) and observation of diffracted electrons as spots on a fluorescent screen.

The history of quantum mechanics is a fundamental part of the history of modern physics. Quantum mechanics' history, as it interlaces with the history of quantum chemistry, began essentially with a number of different scientific discoveries: the 1838 discovery of cathode rays by Michael Faraday; the 1859–60 winter statement of the black-body radiation problem by Gustav Kirchhoff; the 1877 suggestion by Ludwig Boltzmann that the energy states of a physical system could be discrete; the discovery of the photoelectric effect by Heinrich Hertz in 1887; and the 1900 quantum hypothesis by Max Planck that any energy-radiating atomic system can theoretically be divided into a number of discrete "energy elements" ε such that each of these energy elements is proportional to the frequency ν with which each of them individually radiate energy, as defined by the following formula:

References

  1. "Comstock Prize in Physics". National Academy of Sciences. Archived from the original on 29 December 2010. Retrieved 13 February 2011.
  2. 1 2 3 Kelly, Mervin J. (1962). "Davisson1881–1958" (PDF). Biographical Memoirs, Vol. XXXVI. US National Academy of Sciences. pp. 51–84. OCLC   20727455 . Retrieved 2012-12-14.
  3. Nobel Foundation (1937). "Clinton Joseph Davisson: The Nobel Prize in Physics 1937". Les Prix Nobel. Retrieved 2007-09-17.
  4. Davisson, Clinton (1965). "The Discovery of Electron Waves". Nobel Lectures, Physics 1922–1941. Amsterdam: Elsevier Publishing Company. Retrieved 2007-09-17.
  5. "Biographical Memoirs" (PDF).
  6. "Memoirs" (PDF).
  7. "O. W. (Owen Willans) Richardson: An Inventory of His Papers at the Harry Ransom Center". norman.hrc.utexas.edu. Retrieved 2016-01-23.
  8. History, Bill Kemp | Historian/archivist, McLean County Museum of. "Bloomington native won Nobel Prize in physics". pantagraph.com. Retrieved 2016-01-23.
  9. Davisson, Gazetteer of Planetary Nomenclature, International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN)