Z-dependence of the level intervals in 2s 2 2p 2, 2s 2 2p 3 and 2s 2 2p 4

Values of the level intervals in the ground configurations 2s ² 2p ², 2s ² 2p ³ and 2s ² 2p ⁴ have been critically compiled from laboratory observations and from observations of nebular and coronal forbidden transitions. The data are represented within experimental errors by means of semi-empirical extrapolation formulae which contain from 3 to 5 adjusted parameters. The results provide means for checking laboratory and astrophysical identifications and measurements. Tables of best level values are given for the configurations concerned.