The quantized @I03103@ of a molecule in its electronic ground or @E02257@ can be approximated with sufficient accuracy for analytical purposes by: \[E_{\text{int}}=E_{\text{el}}+E_{\text{vib}}+E_{\text{rot}}\] where \(E_{\mathrm{el}}\) is the electronic, \(E_{\mathrm{vib}}\) the vibrational and \(E_{\mathrm{rot}}\) the rotational energy, respectively.