English: Common processes of electron interaction with light. Absorbed radiation may be emitted by vibrational relaxation, fluorescence, or phosphorescence (after intersystem crossing).

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Constants are: ${\displaystyle h}$ Planck's Constant, ${\displaystyle c}$ speed of light, ${\displaystyle D_{e}}$ depth of potential minimum, ${\displaystyle a={\sqrt {m_{\text{eff}}\pi \nu ^{2} \over \hbar cD_{e}}}}$, ${\displaystyle R}$ is the distance from the minimum of the curve ${\displaystyle R_{e}}$ as given by Atkins. ^[1]