Energy levels of Si⁺ ions and different channels of excitation and de-excitation from the ground-state or the fine-structure level (fluorescence) for Si II* λ1265, 1309, 1533 lines in panels (a) to (c), respectively. The probabilities (P) of related transitions and their wavelengths are also shown. The ionization energies of these LIS lines are close to that of H I. The Si II* lines can be regarded as an escape channel of photons from Si II resonant scattering.