natural width of energy level

natural width of energy level

[′nach·rəl ¦width əv ′en·ər·jē ‚lev·əl]
(physics)
A measure of the spread in energy of an excited state of a quantized system due to spontaneous transitions to other states; quantitatively, it is the difference between the energies for which the intensity of emission from or absorption by the state, or of the scattering cross section associated with it, is one-half its maximum value, in the absence of any external influence on the system.