absorption spectrum a spectrum produced when electromagnetic radiation is absorbed by a sample. The frequencies of the radiation absorbed are those able to excite the atoms or molecules of the sample from their ground states to excited states. The frequency, ν, at which a particular absorption line occurs depends on the energy difference, ΔE, between that of a particular ground state and that of the corresponding excited state. It is given by ν = ΔE/h, where h is the Planck constant.
