For a diatomic molecule, the maximum vibrational energy that a molecule can have prior to its @[email protected] into the ground electronic states of the @[email protected] atoms (spectroscopic @[email protected], \(D_{\text{e}}\)). The \(D_{\text{e}}\) value is related to the chemical @[email protected] energy: \(D_{\text{0}}=D_{\text{e}}- \mathrm{E}_{\text{vib}}\left(0\right)\), where \(\mathrm{E}_{\text{vib}}\left(0\right)\) is zero-point vibrational energy. This definition is usually extended to the @[email protected] of polyatomic molecules into certain molecular fragments through homolytic or heterolytic bond cleavages.