Schematic view of the model atom for He I. The blue lines represent the transitions present in the model atom file, both collisional and radiative. The red lines indicate the He I 10 830 Å and He I D₃ spectral lines. Energy levels 1s 2p ³P_0, 1, 2 and 3d ³D_1, 2, 3 are each depicted in the diagram as one energy level, but they consist of three levels each. The total number of levels in the model atom is 16, 12 of which belong to He I.