Grotrian diagrams for the N iii doublet (left) and quartet (right) system. Level numbers refer to Table B.1. Levels # 8, 10, 11 refer to the 3s, 3p and 3d levels involved in the formation of N iiiλλ4634 − 4640 − 4642, and # 3, 4, 5 refer to levels 2p² (²D, ²S, ²P) that drain level 3p via “two electron transitions”. Important optical transitions are indicated by green lines and numbers referring to Table 4 in the main section.