lifetime

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

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

lifetime

[′līf‚tīm]

(physics)

mean life

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.