Species that exhibit charge-transfer absorption are of particular importance because their molar absorptivities are very large (max > 10,000). Thus, these complexes provide a highly sensitive means for detecting and determining absorbing species. Complexes exhibit charge transfer absorption are called charge-transfer complexes. In order for a complex to exhibit a charge-transfer spectrum, it is necessary for one of its components to have electron-donor characteristics and for the other component to have electron-acceptor properties. Absorption of radiation then involves transfer of an electron from the donor to an orbital that is largely associated with the acceptor.