Wan-Ü Lydia Tchang-Brillet

Analysis of the free ion Nd3+ spectrum (Nd IV)

A recent breakthrough in the analysis of Nd IV resulted in the establishment of 37 energy levels of the ground configuration 4f3. We report here the completion to all 41 levels of this configuration. Wavelength measurements extended to 2800 A and in higher excitation conditions lead to the classification of 1426 lines involving the excited configurations 4f25d, 4f26p, 4f26s. Owing to configuration mixing between 5p64f26p and the core-excited 5p54f4, numerous 5p64f25d–5p54f4 transitions, normally dipole-forbidden, are observed. Altogether 111 odd parity levels and 121 even parity ones have been established. Their parametric least-squares fits have rms deviations of 91 cm−1 and 37 cm−1, respectively. The interaction 5p64f25d–5p54f35d has an impact on the 4f3–4f25d transition probabilities computed by means of the Cowan codes. Theoretical values of lifetimes are reported for all the even parity levels.

Theoretical study of ground-state configurations 4fN in Nd IV, Pr IV and Nd V

Although the trivalent lanthanide ions embedded in compounds have a wealth of applications in laser physics and the lighting industry, the theoretical interpretation of their ground-state configurations 4fN in the free ion spectra was restricted by the lack of experimental data. In the first part of this paper, the present status of their group-theoretical description and prospects for improvement are given. In the second part, this description is applied for the first time to a truly isolated configuration 4f3 in Nd IV by performing a parametric fit of level energies, taking into account Coulomb and spin-dependent interactions beyond the first order of perturbation. A root mean square (rms) deviation 5.39 cm−1 (i.e. 1/13 000 of the energy spread of the configuration) is obtained with 23 free parameters and 41 newly determined levels. The contributions of all parameters to the level energies are detailed for the first time. It is shown that energy shifts caused by the effective electrostatic parameters related to the third order of perturbation amount to about 10−3 of the total energy spread of the configuration 4f3. As concerns spin-dependent operators, the relative contributions of the spin–orbit interaction (SO), of the combined effects of spin–other-orbit and configuration interaction (SOO + CI) and of the spin–spin interaction (SS) are in the ratios 571:12:1. The Marvin integrals derived from the experimental energies are in a very good agreement with Hartree–Fock estimates. The ground-state configurations 4f2 of Pr IV and of the newly analysed spectrum Nd V are studied with the same methods.

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 4f 2 5d levels to 37 levels of the 4f 3 ground configuration in the free ion Nd 3+ . The levels 4f 34 F3/2 and 4 I11/2, responsible for the wellknown 1064 nm laser line, have respective positions of 11 698.57 ±0. 1c m −1 and 1897.07 ±0. 1c m −1 above the ground level 4 I9/2. The newly found levels of 4f 3 constitute the first isolated 4f N configuration (N > 2) and therefore enable checks of effective parameters that represent far configuration interaction. Slater parameters F k (4f, 4f) derived from Nd 3+ :LaCl3 are 3% to 5% smaller

Spectrum and energy levels of the Yb4+ free ion (Yb V)

The spectrum of ionized ytterbium produced by a sliding spark source was recorded on the 10 m high resolution vacuum ultraviolet normal-incidence spectrograph of the Meudon Observatory. About 1080 lines attributed to Yb V, hitherto unknown, have been identified. The analysis of this spectrum established all the energy levels of the ground configuration 4f12 and, respectively 174, 12 and 43 levels of the excited configurations 4f115d,4f116s and 4f116p. The theoretical calculations by means of the Cowan codes included a least-squares optimization of the relevant radial parameters by minimizing the differences between calculated and experimental level energies, which led to mean errors of 55 cm−1 for the 56 even parity levels and 51 cm−1 for the 186 odd parity ones. Interactions with the unknown core-excited configurations 5p54f13, 5p54f126p, 5p54f125d and 5p54f126s were taken into account.

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

The 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.

The 3d4-3d34p Transitions of Triply Ionized Manganese (Mn IV)

The analysis of Mn IV is extended in the wavelength range 473-847 A. A total of 600 classified lines are given, of which 372 are newly observed. All of them are due to 3d4-3d34p transitions. Their classification and the identifiication of 59 new levels are supported by the parametric studies of the 3d4 and 3d34p configurations. The ground configuration 3d4 is calculated by taking into account the effective magnetic interactions which improve by an order of magnitude the theoretical fine structure of the quintet and triplet terms. The analysis was guided by the prediction of relative line strengths in intermediate coupling. Calculated energies and LS composition are given for all levels of the configuration, 3d4 and 3d3 4p.