| 1. |
- Gurell, Jonas, 1981-
(författare)
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High Resolution Spectroscopy of Singly Charged Ions : Applications of Laser and Fourier Transform Techniques
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents measurements of fundamental properties of singly charged ionic systems including spectral wavelengths, lifetimes of excited states and branching fractions with the main focus on time resolved laser spectroscopy of stored ions providing lifetime measurements of metastable states. The results of these measurements have been used to determine energy levels and transition probabilities of the studied systems. The included experimental data are compared with results from calculations which provides evaluations of different theoretical models. The presented results have been applied by others to the field of atomic astrophysics in order to deduce electron densities and elemental abundances in ejecta of the supermassive star eta Carinae and have also been followed by additional work of theoreticians interested in comparisons with laboratory data. The thesis is a result of several collaborations in which Stockholm University has been providing lifetime measurements of metastable states, Lund Observatory and the National Institute of Standards and Technology have been providing wavelength and branching fraction measurements, Lund Laser Centre has been providing lifetime measurements of short-lived states and calculations have been performed by theoretical physicists from Université de Mons-Hainaut, Université de Liège, Queen's University of Belfast and Laboratoire Aimé Cotton.
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| 2. |
- Gurell, Jonas, 1981-
(författare)
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Laboratory studies of forbidden decay processes in stored ions
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Measurements of atomic and ionic data has been an active research area since the beginning of spectroscopic studies. The experimental data deduced from thesestudies are of great interest for our understanding of fundamental as well as applied physics. The metastability of certain energy levels has been used toexplain phenomena in widely different fields ranging from the principles of the laser to observations of forbidden spectral lines originating fromastrophysical objects. Eventhough measurements of radiative lifetimes have been carried out for many decades new interesting results are still found in theexplanation of phenomena observed in these studies. The technological development in the field of atomic physics has provided researchers with several toolswhich have opened up completely new possibilities in recent years. Atoms and ions can now be stored for long times which allows studies of extremely weakprocesses. In this thesis results from studies of weak radiative decays of metastable levels are presented. The measurements were carried out utilizing a laserprobing technique together with ions stored in the ion storage ring CRYRING at the Manne Siegbahn laboratory in Stockholm, Sweden. The longest radiativelifetime measured so far in a storage ring, 89 s in singly ionized barium, is presented along with a completely new method for determining extremelylong radiative lifetimes. The thesis also includes new interesting results from lifetime measurements in argon which revealed the unexpected importance of an E3 decay channel. This is to the best of our knowledge the first ever observation of an E3 transition rate of this magnitude in a singlycharged ion. All lifetime measurements are presented with complementary calculations by our collaborators at Université de Mons-Hainaut and Université de Liège, Belgium. The studies of BaII are also part of a collaboration with the Institute of solid state physics of the Bulgarian Academy of Sciences.
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| 3. |
- Gurell, Jonas, 1981-, et al.
(författare)
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Laser-probing measurements and calculations of lifetimes of the 5d 2D3/2 and 5d 2D5/2 metastable levels in Ba II
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:5, s. 052506-
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Tidskriftsartikel (refereegranskat)abstract
- The two metastable levels 5d 2D3∕2 and 5d 2D5∕2 in Ba II both show extremely long lifetimes of the order of several tens of seconds each. This has been found both by experiments and by theoretical predictions. The small transition probabilities associated with these two levels make them interesting and challenging for theoreticians as well as for experimentalists. Several calculations and measurements of these two lifetimes have been made previously but discrepancies between the results are present. This article presents values of τ=89.4±15.6 s for the 2D3∕2 level and τ=32.0±4.6 s for the 2D5∕2 level measured in a beam-laser experiment performed at the ion storage ring CRYRING. These values are supported by our new calculations resulting in τ=82.0 s for the 2D3∕2 level and τ=31.6 s for the 2D5∕2 level.
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| 4. |
- Gurell, Jonas, 1981-, et al.
(författare)
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The FERRUM project : Laboratory-measured transition probabilities for Cr II
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 511:A68
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Tidskriftsartikel (refereegranskat)abstract
- Aims: We measure transition probabilities for Cr II transitions from the z ^4H_J, z ^2D_J, y ^4F_J, and y ^4G_J levels in the energy range 63000 to 68000 cm^{-1}. Methods:Radiative lifetimes were measured using time-resolved laser-induced fluorescence from a laser-produced plasma. In addition, branching fractions were determined from intensity-calibrated spectra recorded with a UV Fourier transform spectrometer. The branching fractions and radiative lifetimes were combined to yield accurate transition probabilities and oscillator strengths. Results: We present laboratory measured transition probabilities for 145 Cr II lines and radiative lifetimes for 14 Cr II levels. The laboratory-measured transition probabilities are compared to the values from semi-empirical calculations and laboratory measurements in the literature.
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| 5. |
- Gurell, Jonas, 1981-, et al.
(författare)
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The FERRUM project : Transition probabilities for forbidden lines in [Fe II] and experimental metastable lifetimes
- 2009
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 508:1, s. 525-529
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Tidskriftsartikel (refereegranskat)abstract
- Context. Accurate transition probabilities for forbidden lines are important diagnostic parameters for low-density astrophysical plasmas. In this paper we present experimental atomic data for forbidden [Fe II] transitions that are observed as strong features in astrophysical spectra. Aims. We measure lifetimes for the 3d(6)((3)G)4s a (4)G(11/2) and 3d(6)((3)D)4s b (4)D(1/2) metastable levels in Fe II and experimental transition probabilities for the forbidden transitions 3d(7) a (4)F(7/2,9/2)-3d(6)((3)G)4s a (4)G(11/2). Methods. The lifetimes were measured at the ion storage ring facility CRYRING using a laser probing technique. Astrophysical branching fractions were obtained from spectra of Eta Carinae, obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The lifetimes and branching fractions were combined to yield absolute transition probabilities. Results. The lifetimes of the a (4)G(11/2) and the b (4)D(1/2) levels have been measured and have the following values, tau = 0.75 +/- 0.10 s and tau = 0.54 +/- 0.03 s respectively. Furthermore, we have determined the transition probabilities for two forbidden transitions of a (4)F(7/2,9/2)-a (4)G(11/2) at 4243.97 and 4346.85 angstrom. Both the lifetimes and the transition probabilities are compared to calculated values in the literature.
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| 6. |
- Gurell, Jonas, 1981-, et al.
(författare)
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Wavelengths, energy levels and HFS in Ho II
- 2009
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 79:3, s. 035306-
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Tidskriftsartikel (refereegranskat)abstract
- We recorded spectra of Ho II emitted by hollow-cathode lamps, using the ultraviolet Fourier transform spectrometer (FTS) at Lund Observatory and the 2-m FTS at the National Institute of Standards and Technology. The combined wavenumber coverage spans the interval from 8000 cm-1 to 49600 cm-1(12500 Å to 2016 Å). We measured 303 lines in these spectra and used them to determine energies and hyperfine structure constants of 100 levels. Ofthese, 41 energy levels have not been reported previously and hyperfine structure constants have not been reported previously for 83 levels. Comparisonsbetween the hyperfine structure constants and energy levels presented in this article and those previously determined from other studies are included anddiscrepancies are discussed. A theoretical study of the odd-parity levels leads to hyperfine structure parameters and to predictions for unknown excited levelsof the ground-state configuration.
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