Alfred Landé
Encyclopedia
Alfred Landé was a German-American physicist known for his contributions to quantum theory
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

. He is responsible for the Landé g-factor
Landé g-factor
In physics, the Landé g-factor is a particular example of a g-factor, namely for an electron with both spin and orbital angular momenta. It is named after Alfred Landé, who first described it in 1921....

 an explanation of the Zeeman Effect
Zeeman effect
The Zeeman effect is the splitting of a spectral line into several components in the presence of a static magnetic field. It is analogous to the Stark effect, the splitting of a spectral line into several components in the presence of an electric field...

.

Life and Achievements

Alfred Landé was born on 13 December 1888 in Elberfeld
Elberfeld
Elberfeld is a municipal subdivision of the German city of Wuppertal; it was an independent town until 1929.-History:The first official mentioning of the geographic area on the banks of today's Wupper River as "elverfelde" was in a document of 1161...

, Germany.

In 1913 Landé was sent by Arnold Sommerfeld
Arnold Sommerfeld
Arnold Johannes Wilhelm Sommerfeld was a German theoretical physicist who pioneered developments in atomic and quantum physics, and also educated and groomed a large number of students for the new era of theoretical physics...

, his thesis advisor at the University of Munich, to be a special assistant for physics to David Hilbert
David Hilbert
David Hilbert was a German mathematician. He is recognized as one of the most influential and universal mathematicians of the 19th and early 20th centuries. Hilbert discovered and developed a broad range of fundamental ideas in many areas, including invariant theory and the axiomatization of...

 at the University of Göttingen, to replace Paul Peter Ewald
Paul Peter Ewald
Paul Peter Ewald was a German-born U.S. crystallographer and physicist, a pioneer of X-ray diffraction methods.-Education:...

, whom Sommerfeld had sent to the same position in 1912. There, Landé also came in close contact with Max Born
Max Born
Max Born was a German-born physicist and mathematician who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics and supervised the work of a number of notable physicists in the 1920s and 30s...

. In physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

, it was the era of the Bohr
Niels Bohr
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...

 atom model. The leaders of Göttinger science included many greats that Landé was to come in contact with including Hilbert, Edmund Landau
Edmund Landau
Edmund Georg Hermann Landau was a German Jewish mathematician who worked in the fields of number theory and complex analysis.-Biography:...

, Carl Runge and Ludwig Prandtl (the noted aerodynamics theoreticist). Also Niels Bohr
Niels Bohr
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...

 and Hendrik Lorentz
Hendrik Lorentz
Hendrik Antoon Lorentz was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect...

 visited Goettingen frequently.

Landé obtained his doctorate under Sommerfeld at the University of Munich, two weeks prior to the start of the First World War
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

. He joined the Red Cross and served for two years on the eastern front before being invited by Max Born to join him at the Artillery Testing Commission, one of the few scientific sections of the army. Apart from their work on artillery location by sound ranging, they began to examine the cohesive forces and compressibility of crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

s. This work led to the unexpected result that the electron trajectories in atoms were not at all like planetary orbits, which at the time was the usual understanding of the electron in an atom.

Landé studied atomic structure intensively for the next seven years. In 1916 Sommerfeld had begun to apply the new atomic theory to form a general quantization rule. Landé's work over cubic and tetrahedral electron trajectories ("cube atoms") became of great interest to Sommerfeld, Peter Debye
Peter Debye
Peter Joseph William Debye FRS was a Dutch physicist and physical chemist, and Nobel laureate in Chemistry.-Early life:...

 and Bohr.

In 1919 Landé unexpectedly turned to spectroscopy
Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...

 even though the continuation of the study of the spatial orientation of the atoms was the most pressing problem of the time. He turned to the problem of atoms with several electrons, in particular to the simplest case, the spectrum of helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

. The spectroscopy of helium had been examined experimentally by Friedrich Paschen
Friedrich Paschen
Louis Karl Heinrich Friedrich Paschen , was a German physicist, known for his work on electrical discharges. He is also known for the Paschen series, a series of hydrogen spectral lines in the infrared region that he first observed in 1908...

, but there did not exist a theoretical interpretation. The spectrum showed non-combining single and double (actually triplet, as it turned out later) terms so that it seemed as if helium was made of two different substances (which is explained today as the result of electron spin
Spin (physics)
In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,...

).

Landé's work contained several new important ideas, including the rule of vector addition of two quantum-mechanical angular momenta J1 and J2. His findings and postulates were later confirmed by quantum theory
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

.

Landé's Frankfurt investigations (December 1920 until April 1921) ended with the discovery of the well-known Landé g-formula and an explanation for the anomalous Zeeman Effect
Zeeman effect
The Zeeman effect is the splitting of a spectral line into several components in the presence of a static magnetic field. It is analogous to the Stark effect, the splitting of a spectral line into several components in the presence of an electric field...

. The Landé g-factor
Landé g-factor
In physics, the Landé g-factor is a particular example of a g-factor, namely for an electron with both spin and orbital angular momenta. It is named after Alfred Landé, who first described it in 1921....

 is now defined through mJ, the magnetic quantum number
Magnetic quantum number
In atomic physics, the magnetic quantum number is the third of a set of quantum numbers which describe the unique quantum state of an electron and is designated by the letter m...

.

In 1923, Landé stated the Landé interval rule
Landé interval rule
In atomic physics, the Landé interval rule states that if the spin-orbit interactions of an electron are weak, the energy levels of each are split. Subsequently, each have a different angular momentum...

, a rule dealing with the relation between an electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

's spin and orbit.

During 1925, Ralph Kronig
Ralph Kronig
Ralph Kronig was a German-American physicist . He is noted for the discovery of particle spin and for his theory of x-ray absorption spectroscopy...

 the discoverer of electron spin was working as an assistant to Landé.

In late 1929 Landé was invited to Ohio State University
Ohio State University
The Ohio State University, commonly referred to as Ohio State, is a public research university located in Columbus, Ohio. It was originally founded in 1870 as a land-grant university and is currently the third largest university campus in the United States...

 in Columbus, to present a series of lectures. After a second stay (1930-1931) in Columbus, Ohio
Columbus, Ohio
Columbus is the capital of and the largest city in the U.S. state of Ohio. The broader metropolitan area encompasses several counties and is the third largest in Ohio behind those of Cleveland and Cincinnati. Columbus is the third largest city in the American Midwest, and the fifteenth largest city...

, he decided to establish himself in the United States. Landé was forerunner of a phase of new interpretation of quantum theory, from which concrete physical statements about experimentally verifiable facts can be made. This happened, after the first phase of the interpretation of the theory with well-known discussions between Louis de Broglie, Erwin Schrödinger
Erwin Schrödinger
Erwin Rudolf Josef Alexander Schrödinger was an Austrian physicist and theoretical biologist who was one of the fathers of quantum mechanics, and is famed for a number of important contributions to physics, especially the Schrödinger equation, for which he received the Nobel Prize in Physics in 1933...

, Bohr and Albert Einstein
Albert Einstein
Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...

, who opted provisionally in favor of the Bohr model. Quantum mechanics was providing many theories to be investigated and proved or disproved at the time. The renewed interest expressed itself in new experiments with new technical methods, on individual quantum systems, individual atoms, electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

s and photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...

s. However, after 1950 (and for the rest of his life), Landé turned energetically against the Copenhagen interpretation
Copenhagen interpretation
The Copenhagen interpretation is one of the earliest and most commonly taught interpretations of quantum mechanics. It holds that quantum mechanics does not yield a description of an objective reality but deals only with probabilities of observing, or measuring, various aspects of energy quanta,...

 of quantum theory, very much as Einstein did, based upon Landé's perception that wave-particle duality was unacceptable. The Landé interpretation is considered a minority interpretation of quantum mechanics
Minority interpretations of quantum mechanics
Quantum mechanics is a highly complex field within physics, rife with apparent paradoxes. There are numerous interpretations within the scientific community, some having more academic following than others...

.

Landé died on 30 October 1976 in Columbus, Ohio.

Books

  • Alfred Landé Principles of Quantum Mechanics (Macmillan/Cambridge, 1937)
  • Alfred Landé Quantum Mechanics (Cambridge University Press, 1951)
  • Alfred Landé Quantum Mechanics (Sir Isaac Pitman & Sons, 1951)
  • Alfred Landé Foundations of Quantum Theory: A Study in Continuity and Symmetry (Yale, 1955)
  • Alfred Landé From Dualism to Unity in Quantum Physics (Cambridge University Press, Cambridge, 1960)
  • Alfred Landé New Foundations of Quantum Mechanics (University Press. 1965)
  • Alfred Landé Quantum Mechanics in a New Key (Exposition Press, 1973)
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK