excitation


excitation
/ek'suy tay"sheuhn, -si-/, n.
1. the act of exciting.
2. the state of being excited.
3. Elect.
a. the application of voltage to an electric device, as an electron-tube circuit, an antenna, or a dynamotor, often for producing a magnetic field in the device.
b. the voltage applied.
4. Physics. a process in which a molecule, atom, nucleus, or particle is excited.
5. Also called drive. Electronics. the varying voltage applied to the control electrode of a vacuum tube.
[1350-1400; ME excitacioun < LL excitation- (s. of excitatio), equiv. to L excitat(us) (ptp. of excitare; see EXCITE) + -ion- -ION]

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Addition of a discrete amount of energy to a system that changes it usually from a state of lowest energy (ground state) to one of higher energy (excited state).

For example, in a hydrogen atom, an excitation energy of 10.2 electron volts is required to move the lone electron from its ground state to its first excited state. The excitation energy stored in excited atoms and nuclei is usually emitted as ultraviolet radiation from atoms and as gamma radiation (see gamma ray) from nuclei as they return to their ground states.

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      in physics, the addition of a discrete amount of energy (called excitation energy) to a system—such as an atomic nucleus, an atom, or a molecule—that results in its alteration, ordinarily from the condition of lowest energy (ground state) to one of higher energy (excited state).

      In nuclear, atomic, and molecular systems, the excited states are not continuously distributed but have only certain discrete energy values. Thus, external energy (excitation energy) can be absorbed only in correspondingly discrete amounts.

      Thus, in a hydrogen atom (composed of an orbiting electron bound to a nucleus of one proton), an excitation energy of 10.2 electron volts is required to promote the electron from its ground state to the first excited state. A different excitation energy (12.1 electron volts) is needed to raise the electron from its ground state to the second excited state.

      Similarly, the protons and neutrons in atomic nuclei constitute a system that can be raised to discrete higher energy levels by supplying appropriate excitation energies. Nuclear excitation energies are roughly 1,000,000 times greater than atomic excitation energies. For the nucleus of lead-206, as an example, the excitation energy of the first excited state is 0.80 million electron volts and of the second excited state 1.18 million electron volts.

      The excitation energy stored in excited atoms and nuclei is radiated usually as visible light from atoms and as gamma radiation from nuclei as they return to their ground states. This energy can also be lost by collision.

      The process of excitation is one of the major means by which matter absorbs pulses of electromagnetic energy (photons), such as light, and by which it is heated or ionized by the impact of charged particles, such as electrons and alpha particles. In atoms, the excitation energy is absorbed by the orbiting electrons that are raised to higher distinct energy levels. In atomic nuclei, the energy is absorbed by protons and neutrons that are transferred to excited states. In a molecule, the energy is absorbed not only by the electrons, which are excited to higher energy levels, but also by the whole molecule, which is excited to discrete modes of vibration and rotation.

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Universalium. 2010.

Look at other dictionaries:

  • excitation — [ ɛksitasjɔ̃ ] n. f. • v. 1300, rare jusqu au XIXe; lat. excitatio 1 ♦ Action d exciter (qqn); ce qui excite. ⇒ encouragement, invitation. « Rien n y manque pour aggraver l émeute, ni les excitations plus vives pour la provoquer » (Taine). ⇒… …   Encyclopédie Universelle

  • Excitation — Ex ci*ta tion . [L. excitatio: cf. F. excitation.] 1. The act of exciting or putting in motion; the act of rousing up or awakening. Bacon. [1913 Webster] 2. (Physiol.) The act of producing excitement (stimulation); also, the excitement produced.… …   The Collaborative International Dictionary of English

  • Excitation — or excitement can refer to:* The excited state of an atom * The excitation (magnetic) provided with an electrical generator or alternator * in ethology, provoking of the emotional state of excitement or agitation **Psychomotor agitation **threat… …   Wikipedia

  • excitation — late 14c., from O.Fr. excitation, from L. excitationem (nom. excitatio), noun of action from pp. stem of excitare (see EXCITE (Cf. excite)) …   Etymology dictionary

  • excitation — excitation. См. возбуждение. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • excitation — index aggravation (exacerbation), dispatch (promptness), instigation, provocation Burton s Legal Thesaurus. William C. Burton. 2006 …   Law dictionary

  • excitation — Excitation, Expergefactio …   Thresor de la langue françoyse

  • excitation — [ek΄sī tā′shən] n. [ME excitacioun < LL excitatio] an exciting or being excited: see EXCITE (esp. senses 4, 5, 6) …   English World dictionary

  • EXCITATION — n. f. Action d’exciter. Excitation au meurtre, à la haine et au mépris du gouvernement. Excitation à la débauche. Les excitations de la presse. Il se dit aussi de l’état de ce qui est excité. L’excitation des esprits. En termes de Médecine,… …   Dictionnaire de l'Academie Francaise, 8eme edition (1935)

  • Excitation — Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom. Sur les autres projets Wikimedia : « Excitation », sur le Wiktionnaire (dictionnaire universel) L excitation (physique), L excitation… …   Wikipédia en Français


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