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Lifetime |
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lifetime
1. a. the length of time a person or animal is alive b. (as modifier): a lifetime supply 2. Physics the average time of existence of an unstable or reactive entity, such as a nucleus, excited state, elementary particle, etc.; mean life lifetime [′līf‚tīm] (physics) Lifetime in physics, the average duration τ of existence of (1) excited states of atoms and molecules, which end with the spontaneous transition of particles to a less excited or basic (unexcited) state; the lifetime is an important characteristic of the energy levels of particles (the lifetime on a level); (2) unstable (radioactive) atomic nuclei as well as elementary particles; their lifetime is linked with their half-life period T by the formula τ = T/In 2; and (3) quasiparticles (elementary excitations) in solids and in liquid helium, particularly electrons and holes in semiconductors. Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content. |
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