A diagram which shows the relative energies of orbitals, configurations, valence
bond structures, or states of reactants and products of a reaction, as a function
of the molecular geometry, or another suitable parameter. An example involves the
interpolation between the energies obtained for the united atoms and the values for
the separated atoms limits.
PAC, 1996, 68, 2223
(Glossary of terms used in photochemistry (IUPAC Recommendations 1996))
on page 2234