Similar to d metal complexes, d octahedral metal complexes have D spectral term.

In spectral terms, orthochromasia refers to maintaining the position of spectral peaks, while metachromasia refers to a shift in wavelength, becoming either shorter or longer.

Considering both weak and strong ligand fields, a Tanabe-Sugano diagram shows the energy splitting of the spectral terms with the increase of the ligand field strength.

In spectral terms this means that new frequencies are generated, the main ones being the sum of the strong and weak frequencies are generated, the main ones being the sum of the strong and weak frequencies and their difference.

On the other hand, when ο is small enough to satisfy and putting the integral becomes In spectral terms the first integral corresponds to a narrow line of infinite amplitude centred on zero frequency and it provides the mean level or direct component of the signal over all time,.