Energy levels of 4f3 in the Nd3+ free ion from emission spectra

The emission spectrum of neodymium produced by vacuum spark sources was observed in the vacuum ultraviolet on two normal-incidence spectrographs. In an initial result, more than 550 lines have been identified as transitions from 85 4f25d levels to 37 levels of the 4f3 ground configuration in the free ion Nd3+. The levels 4f34F3/2 and 4I11/2, responsible for the well-known 1064 nm laser line, have respective positions of 11 698.57 ±0.1 cm-1 and 1897.07 ±0.1 cm-1 above the ground level 4I9/2. The newly found levels of 4f3 constitute the first isolated 4fN configuration (N > 2) and therefore enable checks of effective parameters that represent far configuration interaction. Slater parameters Fk(4f, 4f) derived from Nd3+:LaCl3 are 3% to 5% smaller than in the free ion. (letter to the editor)