Cathodoluminescence in catalysis

When an energetic electron scatters inelastically, an electron from the (filled) valence band can be promoted to the (empty) conduction band creating an electron/hole pair. On recombination, the excess energy is released as a photon, the wavelength of which is well defined by the band-gap transition. The technique is powerful in catalysis it is diagnostic of the electronic/chemical state and is sensitive to point defects. It can be used to probe the distribution of dopants in catalytic oxides. 

In the cathodoluminescence (CL) technique in the EM, the wavelength of light emitted by selective electron stimulation can be directly related to the local band-gap energy of the catalyst material, and the intensity of the signal to the 

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