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used during the construction of the model potential (MP) and one-quasi-particle wave functions of the zeroth approximation, for the calculation of one-quasi-particle diagram contributions, and also for the effective Calculation Of some second order two-The relativistic perturbation theory is applied to the solution of the manyelectron Dirac equation. The theoretical consideration is accomplished for Some Mg-like ions: s v, Ca IX, ~i XI and F~ xv; the energies of all the states l?2s22p631, j l , 3 1 j 2 are calculated. The Ne-like spectra are calculated for the ions with Z = 16-26; all the states of configurations ls22s22ps3s, 3p, 3d and ls22s2p63s, 3p, 3d are considered.The Dirac equation with the central one-particle model potential VJr) is accepted as a zeroth approximation; the model potential imitates the core potential of the closed shells. The empirical information about the energy structures of one electron above the core or one vacancy inside the core is used here to construct the zeroth approximation.The perturbation theory first order correction is calculated exactly, the high order contributions are accounted for effectively. Two main types of high order corrections are investigated: "polarization" interaction of two "above core" particles and effect of the mutual screening of these particles.quasi-particle diagram contributions. Calculations previously made for the ions of the Mg-like series and the Fe-l&e series (two vacancies above the core 3p63d1') showed that already an elementary calculation within the first order of the PT yields cated multi-configurational Hartree-Fock-Pauli method.In the present paper a regular method for the effective inclusion of high order corrections is described. F~~ ions of the Mg I-like and Ne I-like series the allowance for these corrections appreciably improves the results for the transition energies.Of the Same quality as the more sophisti-

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Energy levels, wavelengths, and transition probabilities of the first and second spectra of tungsten, W I and W II, have been compiled. Wavelengths of observed transitions and energy levels derived from those wavelengths have been obtained from a critical evaluation of the available literature. Measured transition probabilities for some of the observed transitions have been compiled from the published literature.

In this compilation we have used data from some 20 references, only two of which were available to C. E. Moore for her 1949 Atomic Energy Levels tables. The new compilation thus includes significant revisions, extensions, and improvements of the earlier data for configurations of the types 1s 2 2snl and 1s 2 2 pnl and also extends the energy range to higher configurations, including those involving 1s electron excitation. The observed wavelengths for some 200 lines are given with their energy-level classifications. The wavelength measurements, which extend from 89 to 31 780 Å, were obtained from emission spectra of hollow-cathode and arc discharges, beam-foil spectra, and far-ultraviolet photoabsorption spectra. In addition to the energy levels derived from these spectra, we include levels obtained from multiphoton resonance-ionization mass spectrometry and projectile-Auger spectroscopy. We have evaluated a number of levels by using series formulas and/or theoretical results; these levels are more accurate than values derived from available wavelength measurements. Wavelengths calculated from energy-level differences are given for all lines; these ''Ritz'' wavelengths are more accurate than the observed values wherever the differences are significant.

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ABSRACT In this critical compilation, all known to us experimental data on the spectrum of neutral carbon were methodically evaluated and supplemented by parametric calculations with Cowan's code. The sources of experimental data vary from laboratory to astrophysical objects and employ different instrumentation from classical grating and Fourier transform spectrometers to precise laser spectroscopy setups and various other modern techniques. This comprehensive evaluation provides accurate atomic data on energy levels and wavelengths (observed and Ritz) with their estimated uncertainties, as well as a uniform description of observed line intensities. In total, 412 energy levels were optimized with the help of selected 1221 best observed lines participating in 1365 transitions in the wavelength region 750 Å to 609.14 µm. In addition, 737 possibly observable transitions are predicted. Critically evaluated transition probabilities for 1616 lines are provided, of which 241 are new. With the accurate energy levels obtained,combined with additional observed data on high Rydberg states, the ionization limit was determined to be 90 820.348(9) cm −1 or 11.2602880(11) eV in fair agreement with the previously recommended value, but more accurate.