For a diatomic molecule, the maximum vibrational energy that a molecule can have prior to its decomposition into the ground electronic states of the constituent atoms (spectroscopic bond-dissociation energy, $D_{\text{e}}$). The $D_{\text{e}}$ value is related to the chemical dissociation 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 dissociation of polyatomic molecules into certain molecular fragments through homolytic or heterolytic bond cleavages.