J T Costello

4s24p2-4s24p5s transitions in Ru XIII, Rh XIV and Pd XV

Spectra of ionised Ru, Rh and Pd have been observed in laser-produced plasmas. From these observations it has been possible to identify 4s24p2-4s24p5s transitions in Ru XIII, Rh XIV and Pd XV which lie near 100 AA in each of these elements.

The 3p photoabsorption spectra of K II and Ca III

The 3p photoabsorption spectra of K II and Ca III have been recorded in the 25-55 eV region using the dual laser plasma technique. With the help of calculations performed with the Cowan code and Rydberg series expansions, many 3p to ns, d transitions have been identified in these ions. Strong LS-term-dependent behaviour arising from 3d wavefunction contraction is seen to influence intensities and quantum defects in the 3p to nd series.

The XUV photoabsorption spectrum of uranium vapour

The XUV photoabsorption spectrum of uranium vapour has been recorded by means of a novel, twin laser-produced plasma technique. The spectrum is dominated by a broad collective resonance and is in good agreement with recent predictions of many-body theory. Within the limits of experimental error, the widths and positions of the peaks are similar to those of the solid but show a slight shift with respect to those observed in UF4 vapour. It is concluded that the 5f potential is largely unaffected on moving from the atom to the solid.

XUV emission from uranium plasmas; the identification of U XIII and U XV

The XUV spectra of uranium in different regimes of conical thickness and in different ion stages have been observed in a laser-produced plasma. The spectra are dominated by 5d-5f transitions which produce an intense compact transition array in the 100 AA region. The profile and extent of this array is strongly sensitive to the density of uranium ions present in the plasma. A number of lines arising from 5d10 to 5d9nl transitions in U VIII and U XV are identified with the aid of Hartree-Fock and Dirac-Fock calculations. The similarities between the spectrum of uranium and those of the lanthanides observed under similar conditions are stressed.

The 1s absorption spectrum of neutral and singly ionized boron

The spectra of neutral and singly ionized boron have been obtained in a dual laser produced plasma experiment. The XUV continuum emitted from the tungsten plasma was used to backlight a boron plasma at variable time delays from 0.40 to 1.5 mu s after its initiation. At the shorter time delays the spectra of both B I and B II were obtained while neutral boron absorption predominated at the longer time delays. In the 60-70 AA region the spectra were found to contain numerous lines arising from K-shell absorption which had not previously been observed. The majority of these features have been identified with the aid of Dirac-Fock calculations.

4p-5s transitions in Cd XII, Cd XIII and Cd XIV

The spectrum of a cadmium plasma produced by a 1.5 J, 25 ns ruby laser is dominated in the 80-110 AA region by 4p-5s transitions in ion stages XII to XIV. A number of lines from the transitions 4p64d-4p54d5s, 4p6-4p55s and 4p5-4p45s have been identified with the aid of Hartree-Fock and Dirac-Fock calculations. In each case isoelectronic extrapolations were also used to assist the analysis.

4s to 4p transitions in As I like Ru XII, Rh XIII and Pd XIV

Analysis of the spectra of laser produced plasmas of ruthenium, rhodium and palladium in the 200-400 AA region has yielded the energies of all the levels of the 4s4p4 configuration in Ru XII and Rh XIII and three of the levels of this configuration in Pd XIV. Improved energy values were obtained for the levels of the 4s24p3 configuration in these ions. The classifications were made by isoelectronic comparison of Dirac-Fock calculations along the As I sequence.

4s24p4-4s24p35s transitions in Ru XI, Rh XII and Pd XIII

The spectra of ionised ruthenium, rhodium and palladium emitted from laser-produced plasmas have been photographed in the 40-250 AA region. From these observations it has been possible to identify the lines arising from 4s24p4-4s24p35s transitions in Ru XI, Rh XII and Pd XIII and establish the levels of these configurations. The classifications are based on Dirac-Fock calculations and isoelectronic extrapolation.

XUV emission from thorium plasmas; the identification of Th XI and Th XIII

The XUV spectra of thorium in three different regimes of optical thickness have been observed in a laser-produced plasma. An intense 5d-5f transition array, the profile and extent of which are strongly sensitive to the thorium ion density, dominates the spectrum. A number of lines belonging to the 5d106s2-5d96s25f, 6p and 5d10-5d95f, 6p transition arrays of Th XI and Th XIII, respectively, are identified with the aid of Hartree-Fock and Dirac-Fock calculations.