Color center

Of main importance for the expected behavior of color centers seems to be ligand field theory.
Basic classification into high spin complex & low spin complex cases.

Main cases include …

• substitutional atoms
• vacancies
• interstitials
• combinations of the above

Imaginable are further exotic cases like e.g. 0D point defects on some type of 1D dislocations or 2D stacking order faults?
Just for one random idea.

For substitutionals atoms the mismatch of atom size can be a factor in energies involved and this frequencies.
Transition metals in silicon being same period similar size and thus rather low energy inclusions => low IR frequencies.

NV centers in diamond

(wiki-TODO: Add some details here.)

Related

• Fluorescence: quick decay right after excitation
• Phosphorescence: very slow decay after excitation ("forbidden" transitions)

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• Ligand field theory
• Fun with spins
• Electronic transitions & Inter system crossing
• Color emulation & Optical effects
• Atomic orbitals

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• mechanooptical conversion
• optomechanical conversion

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• Quasi amorphous structure
• Strained shell structure

External links

• https://en.wikipedia.org/wiki/Ligand_field_theory
• https://en.wikipedia.org/wiki/F-center
• https://en.wikipedia.org/wiki/Crystallographic_defect
• https://en.wikipedia.org/wiki/Solvated_electron (rather exotic case)