Eugene T. Kennedy

New continua for absorption spectroscopy from 40 to 2000 Å

The spectra of plasmas produced by focusing the output of a Q-switched ruby laser (output 1 J) on the rare-earth metals have been studied. From samarium (Z = 62) to ytterbium (Z = 70), strong quasi-uniform continua are emitted in the wavelength range 40–2000 A. Line emission from the target elements is absent over most of this wavelength region, particularly below about 600 A. The use of these continua as simple, reliable background sources for absorption spectroscopy in the vacuum-ultraviolet and soft x-ray region down to 40 A is demonstrated.

Satellite lines of low-Z elements (Li, Be, B) observed in laser-produced plasmas

Satellite lines (thirty-two in all) to the hydrogen- and helium-like resonance series of the low-Z elements, Li, Be and B, have been observed in the emission and absorption spectra of laser-produced plasmas. Hartree-Fock calculations were carried out for the transitions involved and the results were compared with the observations. The behaviour of satellites generally at low-Z values is surveyed.

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.

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.

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.

3p photoabsorption spectra of Mn{sup 2+} and Mn{sup 3+}

Time-resolved extreme ultraviolet photoabsorption spectra of a manganese plasma have been recorded using the dual laser plasma technique. The 43-73 eV photon energy range is dominated by the 3p-3d giant resonance and to a lesser extent the 3p-4s resonances in both Mn{sup 2+} and Mn{sup 3+}, recorded at interplasma time delays of 80 and 30 ns, respectively. These experimentally observed resonances are well reproduced by synthetic spectra calculated using the Hartree-Fock method. The synthetic spectra allow for absorption from excited states of the Mn{sup 2+} and Mn{sup 3+} ions.