The emission spectra of the tripositive lanthanide ion Eu³⁺ have often been employed to probe its environment in the solid state, and the intensity ratio of magnetic dipole (⁵D₀ → ⁷F₁) and forced electric dipole (⁵D₀ → ⁷F₂) transitions has been used to estimate the “degree of asymmetry” of a crystal site. From the site-selective, low temperature emission spectra of Eu³⁺ doped into a glass, a new empirical relation has been found between the width of spectral features and the relative intensity of the ⁵D₀ → ⁷F₀ zero phonon line. In order to explain the observations from experiments with excitation at different wavelengths, a generic quantitative relation has been developed from basic theory and validated from our experimental results. This work gives a deeper insight and understanding of the spectral characteristics of Eu³⁺ electronic spectra in the visible region.