R Hallin

Wavelengths and energy levels of the 4d95s-4d95p transition array of Xe IX

The spectrum of Xe IX in the 400-1200 ? wavelength region has been obtained by observing the radiation emitted following electron capture by Xe9+ and Xe8+ ion beams incident on a He gas target. The xenon ions were produced by the Uppsala University ECR ion source. Many of the stronger lines were found to originate from 4d95s-4d95p transitions. All levels of the 4d95s and 4d95p configurations have been established. The analysis was assisted by MCDF calculations and isoelectronic comparison.

Accurate Experimental Lifetimes of Excited Levels in Nd II

Radiative lifetimes of 24 levels in Nd II have been measured with a laser-ion beam technique using intracavity excitation. Of the lifetimes, 8 were measured with current normalization and 16 with an improved experimental setup using fluorescence light normalization. 11 of the levels have not been measured previously. Several levels were found to have a different lifetime than earlier reported. The measured lifetimes were used to correct old gf-values deduced from arc spectra. These new gf-values together with 17 equivalent widths, obtained from high resolution tracings of the solar disc center spectrum, were used in a solar photosphere abundance analysis which confirmed our old Nd abundance value.

Radiative Lifetimes of Excited Levels in the Homologous Ions Ar II, Kr II and Xe II

Radiative lifetimes of nine of the levels np 4P5/20, np 4D7/2,5/20 and np 2D5/20 in the homologous ions Ar II (n = 4), Kr II (n = 5) and Xe II (n = 6) have been measured with the beam-laser method. The measured lifetimes are compared with lifetime values from other experimental and theoretical works and a thorough discussion of the discrepancies between the results obtained with different techniques is made. Older measurements of transition probabilities are put on an accurate scale using the new lifetime values. The f-values of some strong transitions from levels in the np configuration in Ar II, Kr II and Xe II are compared and are found to be approximately equal.

Hyperfine Structure Measurements in Eu II With Collinear Laser-Ion Beam Technique

Hyperfine structure measurements of the 4f7(8S7/20)6p3/2, (7/2, 3/2)3,4 and 4f7(8S0)5d9D2, 3, 4, 50 levels in 151Eu II and 153Eu II have been performed with collinear laser-ion beam technique. The hyperfine structure constants A and B as well as the nuclear electric quadrupole moments Q have been evaluated.

Radiative Lifetimes and Hyperfine Induced Decay of the 1s 2p 3P2 and 3P0 Levels in Al XIII

The transitions 1s2s 3S1-1s2p 3P2 and 1s2s 3S1-1s2p 3P0 in He-like Al have been observed in a beam-foil experiment at 900 ± 1 A and 953 ± 1 A, respectively. The lifetimes of the upper levels have been determined to 5.4 ± 0.2 ns (3P2) and 4.8 ± 0.2 ns (3P0). We have observed a shortening of the 2p 3P0 lifetime in agreement with theories which consider hyperfine quenching effects, and we give an estimate of the quenching of the level. The wavelengths are compared with theoretical values which include Lamb shift.

Channels of energy transfer to atomic nitrogen in excited argon-nitrogen mixtures

The vacuum ultraviolet (VUV) and ultraviolet (UV) emissions of gaseous mixtures of argon with a small amount of nitrogen were investigated in the afterglow of a pulsed transverse discharge. The time dependences of the intensity of the VUV argon continuum at 126.0 nm, the UV nitrogen molecular band at 337.0 nm, and the VUV nitrogen atomic lines at 149.47 and 174.52 nm were analysed in the total pressure range 150–600 hPa and the range 0.125–1.5 hPa of the admixture concentrations. The results show that all these emissions have a common source of excitation energy, namely the atomic metastable 3P2 state of argon. However, atomic nitrogen also receives energy from the atomic 3P1 state of argon and from the excited Ar2* (1u) molecules.

Hydrogenic Terms and the Ionization Potential of Xe VIII

The spectrum of Xe VIII has been obtained using the beam-foil technique in the wavelength range 500-3000 A. Measured wavelengths of specific hydrogenic transitions and the transitions 5f-5g are given. The hydrogenic terms are represented by the polarization formula and the core dipole polarizability of Xe VIII is derived as 0.45a03 = 0.067 A3. With this formula the ionization limit has been determined as 854 705 ± 75 cm-1 (105.97 ± 0.02 eV).

Beam-foil Spectra of Chlorine and Oxygen Ions at Beam Energies of 6-42 MeV

A tandem accelerator has been used for beam-foil excitation of chlorine and oxygen with beam energies from 6 MeV up to 42 MeV. Hydrogen-like transitions in ClVI to ClXIV and OVI to OVIII have been observed in the wavelength region 2 000-5 700 A. The variation in the intensity of the lines with the beam energy has been used to determine the ionization stage of the ions producing the lines.

VUV emission spectra from binary rare gas mixtures near the resonance lines of Xe I and Kr I

Emission spectra of Xe–X (X = He, Ne, Ar and Kr) and of Kr–Y (Y = He, Ne and Ar) mixtures with low concentrations of the heavier gases (0.1–1%) and moderate total pressures (50–200 hPa) have been recorded near each of the two resonance lines of Xe and Kr in DC glow capillary discharges. The recorded intense emissions have narrow spectral profiles with FWHM of about 0.1 nm. The profiles are very similar in shape to profiles of known high resolution absorption spectra recorded at comparable gas pressures. A tentative identification of the emission structures is given, which involves transitions in heteronuclear molecules and quasimolecules between weakly-bound states.

Wavelengths and energy levels of Xe VII and Xe VIII obtained by collision-based spectroscopy

The Xe VII and Xe VIII spectra have been investigated by collision-based spectroscopy. The radiation emitted following electron capture by 10q keV Xe-q+ ions (q = 6-8) impinging on a He (Ar) gas target has, with some exceptions, been recorded in the 350-8