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Jump to navigationJump to searchCreated page with 'File:lighterstill.jpgright|frame ==Origin== Latin ''excitāre'', frequentative of ''exciēre'' to set in motion, awaken, call forth, in...'
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==Origin==
[[Latin]] ''excitāre'', frequentative of ''exciēre'' to set in [[motion]], [[awaken]], call forth, instigate, < ex- out + ciēre to set in [[motion]].
*[http://en.wikipedia.org/wiki/14th_century 14th Century]
==Definitions==
*1a : to call to [[activity]]
:b : to rouse to an [[emotional]] [[response]] <scenes to excite the hardest man to [[pity]]>
:c : to arouse (as a strong [[emotional]] [[response]]) by appropriate [[stimuli]] <excite enthusiasm for the new regime — Arthur Knight>
*2a : energize <excite an [[electromagnet]]>
:b : to produce a [[magnetic]] field in <excite a dynamo>
*3: to increase the [[activity]] of (as a living [[organism]]) : [[stimulate]]
*4: to raise (as an atomic [[nucleus]], an [[atom]], or a [[molecule]]) to a higher [[energy]] level
==Description==
'''Excitation''' is an elevation in [http://en.wikipedia.org/wiki/Energy_level energy level] above an [[arbitrary]] baseline [[energy]] state. In [[physics]] there is a specific technical [[definition]] for energy level which is often associated with an atom being excited to an excited state.
In [[quantum mechanics]] an excited [[state]] of a [[system]] (such as an [[atom]], [[molecule]] or [[nucleus]]) is any quantum state of the system that has a higher [[energy]] than the [http://en.wikipedia.org/wiki/Ground_state ground state] (that is, more energy than the absolute minimum). The [[temperature]] of a group of [[particles]] is indicative of the level of excitation (with the notable exception of systems that exhibit [http://en.wikipedia.org/wiki/Negative_temperature Negative temperature]).
The lifetime of a [[system]] in an excited state is usually short: [[spontaneous]] or induced emission of a quantum of energy (such as a [http://en.wikipedia.org/wiki/Photon photon] or a [http://en.wikipedia.org/wiki/Phonon phonon]) usually occurs shortly after the system is promoted to the excited state, returning the system to a state with lower energy (a less excited state or the ground state). This return to a lower energy level is often loosely described as decay and is the [[inverse]] of excitation.
Long-lived excited states are often called [http://en.wikipedia.org/wiki/Metastable metastable]. Long-lived [http://en.wikipedia.org/wiki/Nuclear_isomer nuclear isomers] and [http://en.wikipedia.org/wiki/Singlet_oxygen singlet oxygen] are two examples of this.[http://en.wikipedia.org/wiki/Excited_state]
[[Category: Physics]]
==Origin==
[[Latin]] ''excitāre'', frequentative of ''exciēre'' to set in [[motion]], [[awaken]], call forth, instigate, < ex- out + ciēre to set in [[motion]].
*[http://en.wikipedia.org/wiki/14th_century 14th Century]
==Definitions==
*1a : to call to [[activity]]
:b : to rouse to an [[emotional]] [[response]] <scenes to excite the hardest man to [[pity]]>
:c : to arouse (as a strong [[emotional]] [[response]]) by appropriate [[stimuli]] <excite enthusiasm for the new regime — Arthur Knight>
*2a : energize <excite an [[electromagnet]]>
:b : to produce a [[magnetic]] field in <excite a dynamo>
*3: to increase the [[activity]] of (as a living [[organism]]) : [[stimulate]]
*4: to raise (as an atomic [[nucleus]], an [[atom]], or a [[molecule]]) to a higher [[energy]] level
==Description==
'''Excitation''' is an elevation in [http://en.wikipedia.org/wiki/Energy_level energy level] above an [[arbitrary]] baseline [[energy]] state. In [[physics]] there is a specific technical [[definition]] for energy level which is often associated with an atom being excited to an excited state.
In [[quantum mechanics]] an excited [[state]] of a [[system]] (such as an [[atom]], [[molecule]] or [[nucleus]]) is any quantum state of the system that has a higher [[energy]] than the [http://en.wikipedia.org/wiki/Ground_state ground state] (that is, more energy than the absolute minimum). The [[temperature]] of a group of [[particles]] is indicative of the level of excitation (with the notable exception of systems that exhibit [http://en.wikipedia.org/wiki/Negative_temperature Negative temperature]).
The lifetime of a [[system]] in an excited state is usually short: [[spontaneous]] or induced emission of a quantum of energy (such as a [http://en.wikipedia.org/wiki/Photon photon] or a [http://en.wikipedia.org/wiki/Phonon phonon]) usually occurs shortly after the system is promoted to the excited state, returning the system to a state with lower energy (a less excited state or the ground state). This return to a lower energy level is often loosely described as decay and is the [[inverse]] of excitation.
Long-lived excited states are often called [http://en.wikipedia.org/wiki/Metastable metastable]. Long-lived [http://en.wikipedia.org/wiki/Nuclear_isomer nuclear isomers] and [http://en.wikipedia.org/wiki/Singlet_oxygen singlet oxygen] are two examples of this.[http://en.wikipedia.org/wiki/Excited_state]
[[Category: Physics]]
