New calculations have been carried out in intermediate coupling of the wavelengths and intensities of the Fe XXIV transitions ls2nℓ-ls2pnℓ with n ≥ 3.

It is shown that some of these lines are situated on the short wave-length side of the helium-like Fe XXV resonance transition. For the intensities new calculations of the rates of autoionization and radiative decay have been made for the levels involved. Only dielectronic capture has been considered because the contribution of direct inner-shell excitation of the doubly excited states with n ≥ 3 is expected to be small in low density astrophysical plasmas.

For this reason both wavelengths and intensities are compared with the only available solar flare Iron spectra of Grineva et al. (1973). Some features not yet identified in these spectra can be explained with the results of the present calculations. These lead to an important new diagnostic capability for solar flare soft X-ray spectra.

O VI resonance line (2s2S - 2p2PO , 103.19 nm) is formed in the chromosphere-corona transition zone with a temperature of maximum ionization of 350 000°C (Jordan, 1969). The OSO-8/LPSP experiment has observed this line with a 0.006 nm resolution, few arcseconds angular resolution and a time resolution up to few seconds. We present the shape of the line in different areas on the sun (quiet and active). As transition lines are used to determine propagation of wave from chromosphere to corona, we compare width of the O VI line with other measurements obtained with lines of lower ionization temperature. From successive profiles we consider the possibility of direct measurements of wave propagating.

The collaboration between the University of Bonn and Imperial College on the use of synchrotron radiation for the observation of atomic absorption spectra has yielded much new data since IAU Colloquium No.27 (see also E. Radtke's paper in the present meeting). Among recently observed spectra are those of Tl I, In I, Ga I, Pb I, Sn I and Ge I, while earlier data on Zn I and Cd I have been extended to include double excitations. The first evidence of strong mixing between the d-np channel and double excitations at the same energy has come for Tl I where some of the expected d-np series are absent and, instead, other additional series appear.

Several hundred hours of observing time with the University of Colorado spectrometer on 0S0-8 was devoted to rapidly repeated scans of one or two spectral lines while the instrument was pointed at a fixed location on the solar disk. These repeated line scans provide time series of line profiles at a given location on the sun from which we extract information on the line intensity, central wavelength and width. The data reported here are for the λ1816.93 and λ1817.45 lines of SiII. These lines are members of the same multiplet and have a gf ratio of 10:1. The lines were scanned with a slit or 1 x 20 arc second size projected on the sun. About half of the experiments were conducted by scanning only the 1816.93 line with a repeat time of about 15 seconds and about half included alternate scans of line λ1816.93 then λ1817.45 with a repeat time for each line of about 28 seconds.

Energy levels and oscillator strengths are calculated for the 3s23pn–3s23pn–13d transition arrays of Fe X, Fe XI, Fe XII and Fe XIII. The Slater radial integrals for these computations are adjusted so as to become consistent with established energy levels. Pertinent configuration interactions are included and the interaction integrals are reduced by up to 35% from values calculated ab initio, to achieve consistency.

Initial theroretical calculations are made using the ab initio Hartree-X, Slater-Condon programme of Cowan (1967, 1968), the second of which now includes configuration interaction. The first programme computes values for the average energy of the configuration Eav, the electrostatic direct integrals Fk and exchange integrals Gk , the spin-orbit parameters ζ, and the configuration interaction integrals Rk. From these the second programme computes energy levels, wavelengths and oscillator strengths for the transition arrays concerned.

The emission spectrum of the Culham Tokamak, DITE, has been photographed between 10 and 300 Å with spatial and, to a limited extent, temporal resolution. The line spectrum throughout this wavelength range has been interpreted in detail. Apart from well known impurity lines of the light elements, 0, N and C, and of metallic ions of Fe, Cr and Ni, the emission spectrum of DITE is found to be overwhelmingly due to high-stripped Mo ions, the identity of which is confirmed from comparisons with a laser-produced plasma spectrum of Mo and with ab initio Hartree Fock calculations.

In DITE it has been found that Mo ions with degrees of ionisation ranging from XIV to XXIV and above are present. The Mo spectrum may be broadly divided into two distinct regions. In the first, 65-90 Å, a strong dense band of emission lines is observed. These lines may all be accounted for as 3p → 3d transitions in Mo XVI and higher degrees of ionisation.

The second group of Mo lines, between 54 and about 20 Å comprises broad well-spaced bands of emission. The 3d → 4p bands extend below o 35 Å, probably at least as far as Mo XXIV, but are overlapped by other n=3→n = 4 bands, notably 3d → 4f, in lower degrees of ionisation. Inner . subshell transitions are shown to be of some importance in accounting forthe complexity of the merging bands at around 20 Å.