Kastler (Kastler), Alfred( French physicist, Nobel Prize in Physics, 1966)
Comments for Kastler (Kastler), Alfred
Biography Kastler (Kastler), Alfred
May 3, 1902, Mr.. - January 7, 1984
French physicist Alfred Kastler was born in a village Gebviller in Alsace, then belonged to Germany, the family of Frederick and Kastler nee Anna Frey. Children's curiosity and a strong impression produced by the solar eclipse early aroused his interest in science. After graduating from elementary school boy entered Oberrealshule - a real school, renamed after the accession of Alsace to France after the First World War, the Lyceum Bartholdy. In 1920, Mr.. K. was admitted to the Ecole normal syuperer.
At the end of its K. taught physics in secondary schools Myulhausa, Colmar and Bordeaux, and then took a postgraduate course and simultaneously work as an assistant to the University of Bordeaux (1931). In 1936, Mr.. He successfully defended in the same university doctorate in physics, devoted to the excitation of mercury atoms. The next two years to. teaches at the University of Clermont-Ferrand in 1938. appointed full professor of physics at the University of Bordeaux. Upon his return in 1941, in Paris to. taught at the Ecole syuperer normal, and in 1945. was approved at the rank of professor. In this school, he worked until retirement. From 1953 to 1954. K. was a visiting professor at the University of Louvain (Belgium).
The first work to. focused on the interaction between light and electrons in atoms. Speaking simplistically, one can assume that the electrons orbit around the atomic nucleus in different orbits, while rotating around its own axis, like the tops. Quantum theory allows the electrons to move on to definite orbits corresponding to discrete energy levels. Absorbing energy from the incident light, they move to higher energy levels. In reverse transitions at lower levels, the electrons release the previously absorbed energy by emitting light. Like any other form of electromagnetic radiation, light is composed of portions of energy called photons. The energy absorbed or emitted photon is proportional to the frequency of absorbed or emitted light, is equal to the energy difference between the levels between which the transition occurs.
. Atoms of each chemical element has its own special, peculiar only to him a set of allowed energy levels
. Since the excited atoms emit light only at frequencies, . corresponding energy difference between levels, . emission spectrum, . observed, . example, . with the spectroscope, . consist of a series of colored lines (color line corresponds to the frequency of visible light),
. The spectrum allows not only to identify the chemical element, but also to obtain information about the characteristic of its atomic arrangement of energy levels, ie. the structure of its atoms. A closer examination shows that the spectral lines in fact represent a strip of thin, closely spaced lines (fine or hyperfine structure of the atom). Atomic energy levels are a whole set of sublevels. The splitting of the levels of sublevels is determined by various properties of the electron, such as its spin. Details of the atomic structure can be detected from the shift of spectral lines sublevels is happening under the influence of electromagnetic fields. However, optical spectroscopy is not able to accurately separate closely spaced lines.
The late 40-ies. the most sophisticated experiments were done using radiofrequency spectroscopy. One such method, known as the method of magnetic resonance in an atomic beam, is associated with Isidore A. Rabi and his team at Columbia University. Rabi and his colleagues used their method for precise measurements of atomic energy levels in the ground state (ie. in the state with the lowest energy). The ground state can have several magnetic substates, which are slightly separated by a magnetic field. Therefore, acting on the atoms using a magnetic field suitably selected frequency can be induced transition from one sublevel to another. Under properly chosen frequency electromagnetic field is understood as such, in which the photon energy is equal to the energy difference between the sublevels. It is these frequencies lie in the radio. With a special way the magnets and slits, the Colombian team was able to get a narrow beam of atoms in just a few magnetic substates, and the detector can reach only atoms in certain states. If the field is set to the correct frequency, the change in the number of atoms reaching the detector indicates that the transition from one level to another in committing. Knowing the energy of the photons causing transitions, Rabi's group was able to calculate the energy levels corresponding to substates. Such a correspondence between the radio frequency field, causing the transition, and the energy difference between the sublevels is called resonance Hertz (in honor of Heinrich Hertz, who proposed the first experimental proof of the existence of radio waves). Herzen now named and unit frequency.
. Method of magnetic resonance in an atomic beam has its limitations: the average lifetime of the excited state before, . as it will emit energy and will return to the unperturbed ground state, . very small (about one ten millionth seconds), . and only a small number of atoms undergoing induced resonance shift,
. K. with his student, Jean Brossel developed several methods in which light is used to overcome some of the limitations of magnetic resonance in an atomic beam. Method K. called the method of double resonance.
In this method, a beam of light corresponding frequency excites the atoms to a certain energy level. But it is not all sub-levels are occupied. Consequently, when the reverse transitions of atoms in the ground state of the light emitted varies in different directions, in addition, in each direction, it is partially polarized. If the electromagnetic field, . applied to the excited atoms, . has a frequency (energy photons), . necessary, . to induce transitions between the occupied and unoccupied sublevels, . that the emitted light changes as the spatial distribution, . and polarization,
. This change indicates that the radio frequency tuned to the energy difference between the sublevels (which is in resonance with the energy difference). Method K. a means of accurate fixation of the sublevels of the excited atomic states.
In 1950, Mr.. K. reported yet another method, called optical pumping and allow him to move the electrons in atoms with one magnetic sublevel of the ground state to another. In this method, a special way polarized light is directed at a group of atoms. If the ground state has two magnetic sublevels, the atoms on one sublevel absorb light and pass into the excited state, whereas the atoms on the other sublevel do not do. Emits radiation, and returning to the ground state, the atoms occupy and absorbing, and the levels of non-absorbent. In this case we say that light is 'pumped' atoms in a nonabsorbing ground state.
In an effort to further improve their experimental technique, K. and Brossel in 1951. created a special unit in the physics laboratory of the Ecole normal syuperer. Over fifteen years of research of their group and other scientists contributed to the refinement of atomic sublevels and the study of quantum mechanical phenomena.
. In addition to receiving important information about the sublevels of the ground states of many atoms, physicists have learned to orient in the desired direction of the nucleus of atoms in a vapor of mercury and cadmium
. This allowed them to accurately measure some of the magnetic properties of nuclei. Using optical 'pumping', the experimenters were able to create a target, consisting of polarized atoms. Then such a target bombarded by particle beams in experiments on nuclear physics.
To. was awarded the Nobel Prize in Physics 1966. 'for the discovery and development of optical methods for studying Hertzian resonances in atoms'. Introducing the new laureate, Ivar Waller of the Royal Swedish Academy of Sciences focused on describing the nature of the work to. and some conclusions from them. 'A large number of nuclear moments were determined with high accuracy, - said Waller. - Ideas to. relative to the optical 'pumping' played an important role in the creation of the laser. Optical 'pumping' allowed to construct easy to handle and very sensitive magnetometers and atomic clocks. "
Following the resignation in 1968,. K. to 1972. served as head of research at the National Center for Scientific Research.
In 1924, Mr.. K. married schoolteacher Elyse Kosee. In Kastler couple had two sons and a daughter. The unusually modest man abstractedly, K. nonetheless actively participated in a number of political events. He spoke in support of Israel, was a staunch opponent of nuclear weapons, sharply criticized the U.S. role in the Vietnam War. He supported the Algerian independence movement. K. died January 7, 1984, Mr.. Bandol on the French Riviera.
In addition to the Nobel Prize. was awarded Holveka Physical Society of London (1954), award for research of the French Academy of Sciences (1956), an international medal CH.E.K. Misa Optical Society of America (1962) and other honorary awards. He was elected a member of the French Academy of Sciences (1964) and honorary member of scientific societies in Poland, Germany, Hungary and Belgium. In 1952, Mr.. K. become a knight, and in 1977. Commander of the Legion of Honor. K. was an honorary doctorate by the University of Louvain, Pisa and Oxford