CHAVELOT (Schawlow), Arthur L.( American physicist, Nobel Prize in Physics, 1981)
Comments for CHAVELOT (Schawlow), Arthur L.
Biography CHAVELOT (Schawlow), Arthur L.
born May 5, 1921
American physicist Arthur Leonard Schawlow was born in g. Mount Vernon (New York). During the ten years prior to this event, his father, Arthur Schawlow, who immigrated to the United States from Riga (Latvia). Settling in New York, he began working as an agent for insurance and married a Canadian citizen, Helen Mason. When Arthur was three years old, the family (along with born daughter) moved to Canada.
Growing up in Toronto, W. Winchester attended primary school. The normal exemplary school at Teachers College and Vaughan Road College secondary school where he graduated in 1937. He hoped to continue his education and in accordance with yet manifested themselves in his childhood interest in natural sciences chosen specialty radio engineer at the University of Toronto, . but because of the difficulties, . caused depression, . parents could not provide him with adequate material support,
. The dream of a professional radio engineer was not destined to come true, but W. won an honorary scholarship in mathematics and physics. In his own memoirs, 'physics seemed to me very close to radiodelu, so I decided to study physics. "
By that time, when W. received a bachelor's degree (1941), . Canada entered the war, . and he taught courses for military personnel at the University of Toronto until 1944, . then participated in the drafting of a microwave antenna at the factory, . engaged in the manufacture of radar equipment,
. In 1945, Mr.. He returned to the University of Toronto, where the process of performing on the optical spectroscopy under the direction of Mal-kolm F. Crawford, about which he spoke afterwards about how 'extraordinarily creative person'. Stpen doctorate in physics W. received in 1949
Scholarship for post-doctoral companies 'Carbide End Carbon CHEMICALS' allows him to spend two years at Columbia University, working with Charles X. Townes on the problems of microwave spectroscopy.
In 1951, Mr.. SH. is from the laboratory of the company 'Bell' in Murray Hill (New Jersey). The main area of his research is the phenomenon of superconductivity, discovered in 1911. Netherlands physicist Kamerlingh Onnes and consisting in the complete disappearance of electrical resistance in certain substances by cooling them to temperatures close to absolute zero (-273 б¦ C). SH. not broke with Townes. They met at the end of the week and worked on the completion of the book 'Microwave Spectroscopy' ( "Microwave Spectroscopy"), began during the tenure Z. Columbia University. The book was published in 1955
. In the two years before that Townes and his two colleagues have developed a device which they called Mather the first letters of English words: microwave enhancement using induced (stimulated) radiation
. Stimulated emission was predicted by Albert Einstein in 1917. Based on overturning the usual presentation of the new quantum theory, scientists have shown that an atom consists of electrons circulating around the dense central core (model of Niels Bohr). The motion of electrons is limited only allowed discrete orbits, ie. strictly defined energy values. In such cases we say that an atom exists in certain energy states (or at certain energy levels), due to the electron and the nucleus. The lowest level is called the ground state. By absorbing or emitting radiation, electrons can be excited and move to higher levels. As Max Planck showed, . that the radiation consists of individual servings, . which Einstein called quanta (they are now called photons), . energy difference between the levels correspond to a specific quantum, . or photons Planck also showed, . that the frequency of radiation is proportional to the photon energy,
. The excited electron is quickly transferred to a lower energy level, . emitting a photon, . whose energy is equal to the energy difference between these levels, . and giving rise to the characteristic emission spectra, . strictly correlated with the energy difference between levels, . forming a single system for each atom.,
. The excited atoms emit photons are usually random and different wavelengths
. Einstein demonstrated theoretically, . that if a sufficient number of atoms could bring up to a certain energy level, . the radiation, . photons which have energy, . equal to the energy difference between this and any other lower-level atomic, . could cause a cascade of transitions,
. The excited atoms that populate the upper level, stimulated transitions to the lower level with the simultaneous emission of a large number of photons of the same frequency and at the same phase (in the same frequency point of the cycle). Townes experimentally confirmed this theoretical prediction, using microwaves, the photons which have the energy equal to the energy difference between the two atomic levels of ammonia substance with which he worked Towns. (The molecules also have the energy levels, . associated with states of atoms, . constituent molecules, . and the resulting interaction of atoms.) Because the relatively weak microwave signal induces a relatively high yield of photons with the same frequency, . result can be interpreted as a signal gain,
. Some of the released photons excite atoms, forcing them to go back to the upper energy level, resulting in power becomes a generator capable of maintaining sustained oscillations, and not just a single burst.
. Microwaves have a lower frequency (lower energy photons) and, consequently, longer wavelengths (from 1 to 50 mm) than visible light (from 0.0004 to 0.0007 mm)
. In 1957 ... 1958. Towns and W. engaged in finding ways to obtain maser effect on visible light, and in December 1958. published in the journal 'Fizikal Review' ( "Physical Review") the article 'Infrared and optical masers' ( "Infrared and Optical Masers"), which explained how this can be done. In 1960, Mr.. American physicist of the company, Hughes Aircraft 'Theodore Meimeh demonstrated the first functioning laser - abbreviation formed from initial letters of English words: light enhancement using induced (stimulated) radiation. In the same year, W. and other physicists also managed to build lasers. In the same period masers and lasers have been constructed independently from the American physicist Nikolai Basov and Aleksandr Prokhorov.
In 1960, Mr.. SH. returned to Columbia University, this time as a visiting professor. The following year he became professor of physics at Stanford University, where he remains, after spending over five years the dean of the Faculty of Physics. He continues to improve laser technology in an effort to achieve full output of monochromatic (single frequency) radiation with an adjustable frequency (tunable lasers). However, in most of the works W. uses lasers for the study of atoms and molecules, since the early 60-ies. He became one of the leading figures in the rapidly growing field of laser spectroscopy.
. The basis of laser spectroscopy is the fundamental fact, . that atoms and molecules absorb and emit electromagnetic radiation at characteristic frequencies (photon energies), . corresponding energy difference between their different energy levels,
. The frequency spectrum of radiation, . emitted after excitation and the transition to higher energy states, or preferably absorbed from the incident radiation, . helps to identify the elements, . establish the structure of atoms and molecules and to verify the conclusions of the fundamental theory of matter and radiation,
. Creation of tunable lasers has been an important achievement, . since the radiation of this laser is nearly monochromatic (which allows you to accurately measure the frequency), . has a high intensity (which can take spectra at a relatively small number of atoms or molecules) and facilitate the setting of the laser at the desired frequency.,
. In many types of spectroscopy, the spectral line (narrow band), subject to the Doppler effect
. Under the Doppler effect, we understand the change in the observed frequency of the motion of the radiation source relative to the observer. Frequency increases when the emitter is close to the observer, and decreases with distance from the observer, and the magnitude of increase or decrease the frequency depends on how quickly approaching or removed source. In the case of sound waves the Doppler effect is well-known increase or decrease sound the locomotive whistle or whistle a car moving past the observer. In spectroscopy the frequency emitted by atoms or molecules, which are always in motion, depending on their temperatures are shifted upward or downward depending on the direction of their movement. Because the atoms and molecules are moving in different directions, the spectral line broadens.
. In the case of the absorption spectra of 'observer' is an atom or molecule, which decreases radiation 'received' the frequency is higher or lower than the frequency of an external source, depending on whether the moving atom or molecule to the source or the source
. Spectral 'lines' actually represent peaks from falling down the edges. Due to the broadening of the lines, two closely spaced peaks may overlap, and a small peak can be a difficult to background of a larger neighbor, and therefore go unnoticed.
Working together with Theodore in. W. Hцгnsch at Stanford, W. developing several ways to overcome the difficulties associated with the Doppler broadening, through the allocation of the absorption spectra emitted by atoms whose velocity does not contain a component parallel to the laser beam. Since these atoms are not close to the radiation source and is not removed from it, the Doppler effect is completely eliminated. In 1972. SH. and his staff received the first optical spectra of atomic hydrogen, which is not affected by the Doppler effect, which allowed to measure with precision previously unattainable Rydberg constant - one of the most important constants in physics.
. The spectra of molecules, generally speaking, much more complex than the spectra of atoms, and W
. used lasers to simplify the molecular spectra by using the so-called laser tag. Molecules 'pumped up' in a certain energy state with the help of laser radiation, tuned to the desired frequency (photon energy), after which the experimenter observes the return of the lower energy levels. Since this upper state allocated from all possible neighboring states, it is labeled. SH. also developed a method of laser spectroscopy, which allows to determine traces of elements in the surrounding material.
In 1981. SH. Nicolaas Bloembergen with was awarded half the Nobel Prize 'for his contribution to the development of laser spectroscopy'. The other half of the prize was awarded to Kai Sigbanu topics for close work in the field of electronic spectroscopy. At the presentation ceremony of the winners of the representative of the Royal Swedish Academy of Sciences Ingvar Lindgren said:
. 'These methods are allowed to explore the internal structure of atoms, molecules and solids in much greater detail than was possible before. "
. In 1951, Mr.
. SH. married younger sister of Charles X. Aurelia Townes. In the couple has one son and two daughters. Clarinet amateur, W. loves traditional jazz, and gathered a large collection of records. He is known as a lecturer, participated in the creation of educational films and television science programs.
In addition to the Nobel Prize, W. awarded medals and prizes Stuart Ballantyne Franklinovskogo Institute (1952), medals of Thomas Young of London Physics Institute (1963), Frederic Ives medal of the American Optical Society (1976). He is a member of the U.S. National Academy of Sciences. American Association of Basic Sciences, the American Physical Society, the American Optical Society and the Institute of Electrical and Electronics. Among the honorary titles Shavlova - an Honorary Doctorate from the State University of Ghent, Bradford University and the University of Toronto.