Identification of [Fe III] in the solar ultraviolet spectrum
Solar ultraviolet spectra have been obtained with high spectral and spatial resolution using the Naval Research Laboratory's high-resolution telescope and spectrograph1 (HRTS) flown on rockets since 1975 and most recently on the Spacelab 2 Shuttle flight. Because the solar spectrum between ∼1,170 and 1,719 Å has been well observed for some years, few lines of substantial intensity remain unidentified. (See for example the recent compilation by Sandlin et al.2). The longest exposures during the first rocket flight of the HRTS, which obtained spectra with a spatial resolution of ∼ 1 arc s along the slit, of length ∼ 1 solar radius, and a spectral resolution of ∼0.05 Å, showed a number of weak emission lines at the solar limb, in particular between 1,570 and 1,600 Å (see Plates 16 and 17 in ref. 3), that could not readily be identified. Improved observations of these lines were obtained during the flight of HRTS on the Spacelab 2 Shuttle flight in July–August 1985, by making longer exposures (60,100 and 250 s). The scope of the data obtained has been described4. We have now identified the emission lines concerned as forbidden (electric quadrupole and magnetic dipole) transitions in Fe III, the first detection of these particular transitions in any source. They must now be considered potential candidates for previously unidentified lines in other low-density (Ne ≲ 1010 cm−3) astrophysical sources.
Energy Levels of Iron, Fe I through Fe XXVI. Revision,
Abstract : This is a revision of the compilation of energy levels of iron of all ionization stages made in 1975 by Reader and Sugar. New material has since been provided for all but two of these ions. The present compilation includes electron configurations, energy levels, term designations, calculated leading percentages for most ions, experimental g-values, and ionization energies. (Author)
Best approximation and moduli of smoothness: Computation and equivalence theorems
In this paper we investigate the trigonometric series with the @b-general monotone coefficients. First, we study the uniform convergence criterion. The estimates of best approximations and moduli of smoothness of the series in uniform metrics are obtained in terms of coefficients. These results imply several important relations between moduli of smoothness of different orders (in particular, Marchaud-type inequality) and best approximations.