Atomic physics

atomic physics Sector of physics which deals with the study of the atom, and precisely its structure, its constituents and the processes by which atoms interact with other atoms, with electromagnetic radiation and, generically, with other particles. Over the past few decades, thanks to the advent of innovative methodologies, the discipline has made substantial progress.

Atomic physics has been revolutionized in recent years by new methods for controlling the speed and position of atoms and cooling atomic gases to temperatures close to absolute zero. In a gas, atoms move in all directions with speeds that depend on temperature. At room temperature, the velocity of the atoms is 102 ÷ 103 m / s, depending on the atomic mass. In many experiments, it is necessary to have atoms with very low velocities and high densities, without this varying their intrinsic properties. The cooling method based on the collisions of the atoms with the walls of a cold container is limited to temperatures above that of the condensation of the gas, while cooling techniques, in which the atoms interact with the radiation emitted by a laser, allow to reach extremely low temperatures, up to 10-6 K: the coherence properties allow to consider laser radiation as a very low temperature system, so as to decrease the kinetic energy of the atoms, transferring it in part to the electromagnetic field. With these techniques, the cooled atoms can be confined in traps, delimited not by material walls, but by electromagnetic fields. Therefore, atomic samples with very low speeds and high densities are available, ideal for high resolution spectroscopy, collision physics and atomic optics experiments. partially transferring it to the electromagnetic field. With these techniques, the cooled atoms can be confined in traps, delimited not by material walls, but by electromagnetic fields. Therefore, atomic samples with very low speeds and high densities are available, ideal for high resolution spectroscopy, collision physics and atomic optics experiments. partially transferring it to the electromagnetic field. With these techniques, the cooled atoms can be confined in traps, delimited not by material walls, but by electromagnetic fields. Therefore, atomic samples with very low speeds and high densities are available, ideal for high resolution spectroscopy, collision physics and atomic optics experiments.

In very high resolution spectroscopy, the use of cooled atoms allows to drastically reduce the causes of enlargement of the atomic lines, up to the limit of their natural width. One possible application is the development of atomic clocks used as time and frequency samples. In several laboratories, work is underway on the cooling and entrapment of neutral atoms or ions and on the study of the most suitable configurations to eliminate the effects that can limit the measurement / “> measurement of the frequency of the optical transitions. For the direct measurement of the frequency of the transitions Atomic, John L. Hall and Theodor W. Hänsch had in 2005 theNobel prize for physics.

Cooling and laser trapping techniques have also allowed the development of atomic optics with atoms instead of photons. Devices similar to those of traditional optics (mirrors, lenses and beam separators) have allowed atomic interferometry experiments to be carried out, e.g., analogous to Young’s experiment, with observation of interference fringes due to the passage of atoms in a double slit.

In recent years, the development of cooling techniques has led to the direct observation of Bose-Einstein condensation, a phenomenon predicted by Einstein in 1924 and obtained for the first time in 1995. Developments in the same cooling techniques have made it possible to obtain also quantum gases of fermions and ultra-cold mixtures of different atomic species.

With the very low temperatures at which atomic samples can be produced, the physics of collisions in unexplored regimes can also be investigated, since the de Broglie wavelength of atoms becomes comparable with their interaction distances. Finally, interesting perspectives opened by the entrapment of atoms over long times arise from the study of radioactive or antimatter samples for the verification of fundamental theories and laws of symmetry.

 

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