Spectrum and energy levels of the Nd4+ free ion (Nd V)

International audienceThe spectrum of neodymium excited by a sliding spark source was photographed on two vacuum ultraviolet normal-incidence spectrographs. About 250 lines attributed to Nd V, hitherto unknown, have been identified. The analysis of this spectrum established all the energy levels of the configurations 4f2, 4f5d, 4f6s and 4f6p (except for 4f2 1S0). Altogether, 48 known levels classify about 160 lines. Their theoretical calculation includes a least-squares fit with an rms error of 28 cm-1 for the even-parity levels and 26 cm-1 for the odd-parity ones, as well as the best values for relevant radial interaction parameters. In particular, interactions with the core-excited configurations 5p54f3 and 5p54f25d are discussed. Intensities derived from phosphor image plates are used to estimate an effective temperature in the spark of Teff=3.6 eV