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Atomic physics

April 21, 2023

For the classical view of the atom which developed into atomic physics, see atomic theory.

Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. Atomic physics typically refers to the study of atomic structure and the interaction between atoms.[1] It is primarily concerned with the way in which electrons are arranged around the nucleus and the processes by which these arrangements change. This comprises ions, neutral atoms and, unless otherwise stated, it can be assumed that the term atom includes ions.

The term atomic physics can be associated with nuclear power and nuclear weapons, due to the synonymous use of atomic and nuclear in standard English. Physicists distinguish between atomic physics—which deals with the atom as a system consisting of a nucleus and electrons—and nuclear physics, which studies nuclear reactions and special properties of atomic nuclei.

As with many scientific fields, strict delineation can be highly contrived and atomic physics is often considered in the wider context of atomic, molecular, and optical physics. Physics research groups are usually so classified.

Isolated atoms

Atomic physics primarily considers atoms in isolation. Atomic models will consist of a single nucleus that may be surrounded by one or more bound electrons. It is not concerned with the formation of molecules (although much of the physics is identical), nor does it examine atoms in a solid state as condensed matter. It is concerned with processes such as ionization and excitation by photons or collisions with atomic particles.

While modelling atoms in isolation may not seem realistic, if one considers atoms in a gas or plasma then the time-scales for atom-atom interactions are huge in comparison to the atomic processes that are generally considered. This means that the individual atoms can be treated as if each were in isolation, as the vast majority of the time they are. By this consideration, atomic physics provides the underlying theory in plasma physics and atmospheric physics, even though both deal with very large numbers of atoms.

Electronic configuration

Electrons form notional shells around the nucleus. These are normally in a ground state but can be excited by the absorption of energy from light (photons), magnetic fields, or interaction with a colliding particle (typically ions or other electrons).

 
In the Bohr model, the transition of an electron with n=3 to the shell n=2 is shown, where a photon is emitted. An electron from shell (n=2) must have been removed beforehand by ionization

Electrons that populate a shell are said to be in a bound state. The energy necessary to remove an electron from its shell (taking it to infinity) is called the binding energy. Any quantity of energy absorbed by the electron in excess of this amount is converted to kinetic energy according to the conservation of energy. The atom is said to have undergone the process of ionization.

If the electron absorbs a quantity of energy less than the binding energy, it will be transferred to an excited state. After a certain time, the electron in an excited state will "jump" (undergo a transition) to a lower state. In a neutral atom, the system will emit a photon of the difference in energy, since energy is conserved.

If an inner electron has absorbed more than the binding energy (so that the atom ionizes), then a more outer electron may undergo a transition to fill the inner orbital. In this case, a visible photon or a characteristic X-ray is emitted, or a phenomenon known as the Auger effect may take place, where the released energy is transferred to another bound electron, causing it to go into the continuum. The Auger effect allows one to multiply ionize an atom with a single photon.

There are rather strict selection rules as to the electronic configurations that can be reached by excitation by light — however, there are no such rules for excitation by collision processes.

History and developments

Main article: Atomic theory

One of the earliest steps towards atomic physics was the recognition that matter was composed of atoms. It forms a part of the texts written in 6th century BC to 2nd century BC, such as those of Democritus or Vaiśeṣika Sūtra written by Kaṇāda. This theory was later developed in the modern sense of the basic unit of a chemical element by the British chemist and physicist John Dalton in the 18th century. At this stage, it wasn't clear what atoms were, although they could be described and classified by their properties (in bulk). The invention of the periodic system of elements by Dmitri Mendeleev was another great step forward.

The true beginning of atomic physics is marked by the discovery of spectral lines and attempts to describe the phenomenon, most notably by Joseph von Fraunhofer. The study of these lines led to the Bohr atom model and to the birth of quantum mechanics. In seeking to explain atomic spectra, an entirely new mathematical model of matter was revealed. As far as atoms and their electron shells were concerned, not only did this yield a better overall description, i.e. the atomic orbital model, but it also provided a new theoretical basis for chemistry (quantum chemistry) and spectroscopy.

Since the Second World War, both theoretical and experimental fields have advanced at a rapid pace. This can be attributed to progress in computing technology, which has allowed larger and more sophisticated models of atomic structure and associated collision processes. Similar technological advances in accelerators, detectors, magnetic field generation and lasers have greatly assisted experimental work.

Significant atomic physicists

Pre quantum mechanics
Post quantum mechanics

See also

Bibliography

  • Bransden, BH; Joachain, CJ (2002). Physics of Atoms and Molecules (2nd ed.). Prentice Hall. ISBN 978-0-582-35692-4.
  • Foot, CJ (2004). Atomic Physics. Oxford University Press. ISBN 978-0-19-850696-6.
  • Herzberg, Gerhard (1979) [1945]. Atomic Spectra and Atomic Structure. New York: Dover. ISBN 978-0-486-60115-1.
  • Condon, E.U. & Shortley, G.H. (1935). The Theory of Atomic Spectra. Cambridge University Press. ISBN 978-0-521-09209-8.
  • Cowan, Robert D. (1981). The Theory of Atomic Structure and Spectra. University of California Press. ISBN 978-0-520-03821-9.
  • Lindgren, I. & Morrison, J. (1986). Atomic Many-Body Theory (Second ed.). Springer-Verlag. ISBN 978-0-387-16649-0.

References

  1. ^ Demtröder, W. (2006). Atoms, molecules and photons : an introduction to atomic-, molecular-, and quantum-physics. Berlin: Springer. ISBN 978-3-540-32346-4. OCLC 262692011.

External links

 
Wikimedia Commons has media related to Atomic physics.
  • MIT-Harvard Center for Ultracold Atoms
  • Stanford QFARM Initiative for Quantum Science & Enginneering
  • Joint Quantum Institute at University of Maryland and NIST
  • ORNL Physics Division

April 21, 2023
atomic, physics, classical, view, atom, which, developed, into, atomic, physics, atomic, theory, this, article, includes, list, general, references, lacks, sufficient, corresponding, inline, citations, please, help, improve, this, article, introducing, more, p. For the classical view of the atom which developed into atomic physics see atomic theory This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations September 2015 Learn how and when to remove this template message Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus Atomic physics typically refers to the study of atomic structure and the interaction between atoms 1 It is primarily concerned with the way in which electrons are arranged around the nucleus and the processes by which these arrangements change This comprises ions neutral atoms and unless otherwise stated it can be assumed that the term atom includes ions The term atomic physics can be associated with nuclear power and nuclear weapons due to the synonymous use of atomic and nuclear in standard English Physicists distinguish between atomic physics which deals with the atom as a system consisting of a nucleus and electrons and nuclear physics which studies nuclear reactions and special properties of atomic nuclei As with many scientific fields strict delineation can be highly contrived and atomic physics is often considered in the wider context of atomic molecular and optical physics Physics research groups are usually so classified Contents 1 Isolated atoms 2 Electronic configuration 3 History and developments 4 Significant atomic physicists 5 See also 6 Bibliography 7 References 8 External linksIsolated atoms EditAtomic physics primarily considers atoms in isolation Atomic models will consist of a single nucleus that may be surrounded by one or more bound electrons It is not concerned with the formation of molecules although much of the physics is identical nor does it examine atoms in a solid state as condensed matter It is concerned with processes such as ionization and excitation by photons or collisions with atomic particles While modelling atoms in isolation may not seem realistic if one considers atoms in a gas or plasma then the time scales for atom atom interactions are huge in comparison to the atomic processes that are generally considered This means that the individual atoms can be treated as if each were in isolation as the vast majority of the time they are By this consideration atomic physics provides the underlying theory in plasma physics and atmospheric physics even though both deal with very large numbers of atoms Electronic configuration EditElectrons form notional shells around the nucleus These are normally in a ground state but can be excited by the absorption of energy from light photons magnetic fields or interaction with a colliding particle typically ions or other electrons In the Bohr model the transition of an electron with n 3 to the shell n 2 is shown where a photon is emitted An electron from shell n 2 must have been removed beforehand by ionizationElectrons that populate a shell are said to be in a bound state The energy necessary to remove an electron from its shell taking it to infinity is called the binding energy Any quantity of energy absorbed by the electron in excess of this amount is converted to kinetic energy according to the conservation of energy The atom is said to have undergone the process of ionization If the electron absorbs a quantity of energy less than the binding energy it will be transferred to an excited state After a certain time the electron in an excited state will jump undergo a transition to a lower state In a neutral atom the system will emit a photon of the difference in energy since energy is conserved If an inner electron has absorbed more than the binding energy so that the atom ionizes then a more outer electron may undergo a transition to fill the inner orbital In this case a visible photon or a characteristic X ray is emitted or a phenomenon known as the Auger effect may take place where the released energy is transferred to another bound electron causing it to go into the continuum The Auger effect allows one to multiply ionize an atom with a single photon There are rather strict selection rules as to the electronic configurations that can be reached by excitation by light however there are no such rules for excitation by collision processes History and developments EditMain article Atomic theory One of the earliest steps towards atomic physics was the recognition that matter was composed of atoms It forms a part of the texts written in 6th century BC to 2nd century BC such as those of Democritus or Vaiseṣika Sutra code san promoted to code sa written by Kaṇada code san promoted to code sa This theory was later developed in the modern sense of the basic unit of a chemical element by the British chemist and physicist John Dalton in the 18th century At this stage it wasn t clear what atoms were although they could be described and classified by their properties in bulk The invention of the periodic system of elements by Dmitri Mendeleev was another great step forward The true beginning of atomic physics is marked by the discovery of spectral lines and attempts to describe the phenomenon most notably by Joseph von Fraunhofer The study of these lines led to the Bohr atom model and to the birth of quantum mechanics In seeking to explain atomic spectra an entirely new mathematical model of matter was revealed As far as atoms and their electron shells were concerned not only did this yield a better overall description i e the atomic orbital model but it also provided a new theoretical basis for chemistry quantum chemistry and spectroscopy Since the Second World War both theoretical and experimental fields have advanced at a rapid pace This can be attributed to progress in computing technology which has allowed larger and more sophisticated models of atomic structure and associated collision processes Similar technological advances in accelerators detectors magnetic field generation and lasers have greatly assisted experimental work Significant atomic physicists EditPre quantum mechanicsJohn Dalton Joseph von Fraunhofer Johannes Rydberg J J Thomson Ernest Rutherford Democritus Vaiseṣika Sutra code san promoted to code saPost quantum mechanicsAlexander Dalgarno David Bates Niels Bohr Max Born code deu promoted to code de Clinton Joseph Davisson Paul A M Dirac Enrico Fermi code ita promoted to code it Charlotte Froese Fischer Vladimir Fock code rus promoted to code ru Douglas Hartree Ernest M Henley Ratko Janev code mkd promoted to code mk Daniel Kleppner Harrie S Massey Nevill Mott I I Rabi Norman Ramsey Mike Seaton John C Slater George Paget ThomsonSee also EditParticle physics Isomeric shift Atomic engineeringBibliography EditBransden BH Joachain CJ 2002 Physics of Atoms and Molecules 2nd ed Prentice Hall ISBN 978 0 582 35692 4 Foot CJ 2004 Atomic Physics Oxford University Press ISBN 978 0 19 850696 6 Herzberg Gerhard 1979 1945 Atomic Spectra and Atomic Structure New York Dover ISBN 978 0 486 60115 1 Condon E U amp Shortley G H 1935 The Theory of Atomic Spectra Cambridge University Press ISBN 978 0 521 09209 8 Cowan Robert D 1981 The Theory of Atomic Structure and Spectra University of California Press ISBN 978 0 520 03821 9 Lindgren I amp Morrison J 1986 Atomic Many Body Theory Second ed Springer Verlag ISBN 978 0 387 16649 0 References Edit Demtroder W 2006 Atoms molecules and photons an introduction to atomic molecular and quantum physics Berlin Springer ISBN 978 3 540 32346 4 OCLC 262692011 External links Edit Wikimedia Commons has media related to Atomic physics MIT Harvard Center for Ultracold Atoms Stanford QFARM Initiative for Quantum Science amp Enginneering Joint Quantum Institute at University of Maryland and NIST Atomic Physics on the Internet JILA Atomic Physics ORNL Physics Division Retrieved from https en wikipedia org w index php title Atomic physics amp oldid 1147433735, wikipedia, wiki, book, books, library,

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