Spontaneous emission

Spontaneous emission is the process by which an atom or molecule in an excited state drops to the ground state, resulting in the creation of a photon.

Related Topics:
Atom - Molecule - Excited state - Ground state - Photon

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If the atom is in the excited state with energy E_2, it may spontaneously decay into the ground state, with energy E_1, releasing the difference in energies between the two states as a photon. The photon will have frequency u and energy h u, given by:

Related Topics:
Frequency - Energy

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:E_2 - E_1 = h u,

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where h is Planck's constant. The phase of the photon in spontaneous emission is random as is the direction the photon propagates in. This is not true for stimulated emission.

Related Topics:
Planck's constant - Phase - Stimulated emission

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An energy level diagram illustrating the process is shown below:

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Before emission After emission

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