Arne Arnesen

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.

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.

Measurements of absolute transition probabilities in Ba ii through optical nutation: erratum

We have developed a method to measure absolute transition probabilities for ions by recording optical nutation. Ions in an accelerated beam are brought into resonance with a counterpropagating laser beam by a rapid Doppler switch. From the time evolution of the population of the upper level in the resonant transition, we determine the Rabi frequency of the transition. An accurate measurement of the electric field strength then yields the transition probability. We report measurements for five transitions in Ba ii. For three of these transitions our values are more accurate than those of earlier published results.

Isotope shifts and hyperfine structure of 134-138Ba II by fast ion beam-laser spectroscopy

We have measured the isotope shifts of the 5d to 6p transitions in 134-138Ba II, of which the 5d3/2 to 6p1/2 transition has not been measured earlier. We have also obtained values with improved accuracy of the magnetic dipole and electric quadrupole hyperfine coupling constants of the 6p 2Po1/2,3/2 levels in 135,137Ba II. The measurements are performed in the red and orange parts of the optical spectrum using fast ion beam-laser spectroscopy with an improved procedure which avoids calibration of the ion velocity. A comparison with theory is made.

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.

Radiative lifetimes in Sm II and the solar samarium abundance

Radiative lifetimes of 18 levels in Sm II have been measured using the beam-laser technique. For 11 of the levels the lifetimes have not been measured before. The measured lifetimes were used to put old relative gf-values obtained from emission measurements on an absolute scale. These absolute gf-values were subsequently used in a determination of the solar photospheric abundance of samarium by means of synthesis of the solar spectrum. The estimated solar samarium abundance is ASm = 1.02 ± 0.11 dex.

Radiative lifetimes in Nd II and the solar neodymium abundance

Radiative lifetimes of the eight levels 4f4(5I)6p 6K9/2,11/2,13/2,15/2,17/2,19/20, 4f4(5I)6p (27 448)13/20 and 4f4(5I)6p (29 027)17/20 in Nd II were measured with a laser-ion beam technique using intracavity excitation. The lifetimes of three of the levels have not been measured previously. Four lifetimes were found to be significantly shorter than earlier reported. The measured lifetimes were used to correct old gf-values deduced from arc spectra. The improved gf-values were subsequently used in a solar photosphere abundance analysis based on modern solar models and high resolution solar spectra. The Nd abundance was found to be almost twice as large as that previously reported from photosphere analysis and in very good agreement with meteoritic data. The abundance is ANd = 1.47 ± 0.07 on the scale where ANd = log (NNd/NH) + 12.

Collision-based spectroscopy of Xe viii Rydberg states

The photon emission from 60-keV Xe6+ colliding with Na or Ar was recorded in the 35–800-nm wavelength region. Several of the observed lines were classified as transitions from singly excited states in Xe5+. The dipole polarizability of Xe6+ and the ionization energy of Xe5+ were determined from a fit with the polarization formula to the experimentally determined energy levels of nonpenetrating states. The analysis was assisted by Hartree–Fock calculations. All Xe5+ lines in the range 35–800 nm, reported in this work or previously, are tabulated.The photon emission from 60-keV Xe6+ colliding with Na or Ar was recorded in the 35–800-nm wavelength region. Several of the observed lines were classified as transitions from singly excited states in Xe5+. The dipole polarizability of Xe6+ and the ionization energy of Xe5+ were determined from a fit with the polarization formula to the experimentally determined energy levels of nonpenetrating states. The analysis was assisted by Hartree–Fock calculations. All Xe5+ lines in the range 35–800 nm, reported in this work or previously, are tabulated.