| 1. |
- Andersson, Pontus, 1971, et al.
(author)
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Radiative lifetimes of metastable states of negative ions
- 2006
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622 .- 2469-9926 .- 2469-9934. ; 73, s. 032705-
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Journal article (peer-reviewed)abstract
- We present a technique for measuring the radiative lifetimes of metastable states of negative ions that involves the use of a heavy-ion storage ring. The method has been applied to investigate the radiative decay of the np(3) P-2(1/2) levels of Te-(n=5) and Se-(n=4) and the 3p(3) D-2 state of Si- for which the J=3/2 and 5/2 levels were unresolved. All of these states are metastable and decay primarily by emission of E2 and M1 radiation. Multi Configuration Dirac-Hartree-Fock calculations of rates for the transitions in Te- and Se- yielded lifetimes of 0.45 s and 4.7 s, respectively. The measured values agree well with these predicted values. In the case of the D-2 state of Si-, however, our measurement was only able to set a lower limit on the lifetime. The upper limit of the lifetime that can be measured with our apparatus is set by how long the ions can be stored in the ring, a limit determined by the rate of collisional detachment. Our lower limit of 1 min for the lifetime of the D-2 state is consistent with both the calculated lifetimes of 162 s for the D-2(3/2) level and 27.3 h for the D-2(5/2) level reported by O'Malley and Beck and 14.5 h and 12.5 h, respectively, from our Breit-Pauli calculations.
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| 2. |
- Biémont, E, et al.
(author)
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Decay of metastable states in Nd II
- 2007
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In: The European physical journal D Atomic, molecular and optical physics. ; 41, s. 211-
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Journal article (peer-reviewed)
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| 3. |
- Biémont, É., et al.
(author)
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Decay of metastable states in NdII
- 2007
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In: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 41:2, s. 211-219
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Journal article (peer-reviewed)abstract
- The difficulty associated with an accurate determination of transition rates for forbidden lines in lowly ionized heavy elements is illustrated in the case of Nd II. We have investigated the radiative decay of the low-lying metastable levels in Nd+ including the two levels 4f(4)(I-5) 5d K-6(11/2) and 4f(4)(I-5) 5d I-6(13/2). In these two particular cases, using di. erent theoretical approaches, we. nd that the decay is dominated by the M1 channels but that the E2 contributions are of the same order of magnitude. These levels have also been studied experimentally by lifetime measurements with the heavy ion storage ring CRYRING of Stockholm University. The difficulties encountered when performing such experiments are underlined and discussed.
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| 4. |
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| 5. |
- Biemont, E, et al.
(author)
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Importance of an M2 depopulating channel for a KrII metastable state
- 2004
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:6, s. 063003-
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Journal article (peer-reviewed)abstract
- An experimental investigation of the radiative lifetime of the metastable 4s(2)4p(4)(P-3)4d D-4(7/2) level in Kr II shows an unusual situation regarding the importance of an M2 depopulation channel. While the first order M1 and E2 channels are expected to contribute in a dominant way to the decay, the experimental result, obtained using a laser probing technique on a stored ion beam, tau=0.57+/-0.03 s, is far too short to be due to these channels according to our relativistic multiconfiguration Dirac-Fock calculation. Only if second order contributions to the decay branches (including essentially the M2 contribution) are taken into account in the calculations could the unexpected short lifetime be explained.
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| 6. |
- Gurell, Jonas, 1981-, et al.
(author)
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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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In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:5, s. 052506-
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Journal article (peer-reviewed)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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| 7. |
- Gurell, J., et al.
(author)
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Laser-probing measurements and calculations of lifetimes of the 5d D-2(3/2) and 5d D-2(5/2) metastable levels in BaII
- 2007
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:5, s. 052506-
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Journal article (peer-reviewed)abstract
- The two metastable levels 5d(2)D(3/2) and 5d(2) D-5/2 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 ??? = 89.4 +/- 15.6 s for the D-2(3/2) level and ??? = 32.0 +/- 4.6 s for the D-2(5/2) level measured in a beam-laser experiment performed at the ion storage ring CRYRING. These values are supported by our new calculations resulting in ???= 82.0 s for the D-2(3/2) level and ???= 31.6 s for the D-2(5/2) level.
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| 8. |
- Hartman, Henrik, et al.
(author)
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The FERRUM project : experimentally determined metastable lifetimes and transition probabilities for forbidden [Ti II] lines observed in eta Carinae
- 2005
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 361:1, s. 206-210
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Journal article (peer-reviewed)abstract
- In the spectrum of an emission-line region ejected from the massive star Eta Carinae, called the strontium filament (SrF), forbidden lines from many elements, in particular [Sr II] and [Ti II], are observed. These lines are strong in this specific region and valuable for plasma diagnostics. Forbidden lines are not easily produced in laboratory light sources and the atomic parameters for these lines can thus not be measured in a straightforward way. We use a combination of laboratory and astrophysical measurements to determine transition probabilities for the [Ti II] lines. Lifetimes for metastable levels in Ti II are measured using a laser probing technique on a stored ion beam at CRYRING, MSL, Stockholm. Branching fractions from some of these levels are derived from Hubble Space Telescope/STIS spectra of the SrF. The astrophysical branching fractions are combined with the experimental lifetimes to determine absolute transition probabilities. We report lifetimes for the Ti II levels b(4)P(3/2), b(2)P(1/2), c(2)D(3/2) and c(2)D(5/2), in the range 0.29-17 s, and transition probabilities for eight parity-forbidden lines from the levels c(2)D(3/2) and c(2)D(5/2), along with uncertainty estimates.
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| 9. |
- Hartman, Henrik, et al.
(author)
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The FERRUM project: an extremely long radiative lifetime in Ti II measured in an ion storage ring
- 2003
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In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36, s. 197-202
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Journal article (peer-reviewed)abstract
- We have extended the laser probing technique at the CRYRING storage ring to measurement of the extremely long lifetime (28 s) of the metastable 3d2(3P)4s b 4P5/2 level in Ti II. The result obtained demonstrates the power of this method for investigation of such long-lived levels. This is the first experimental lifetime investigation of metastable states in Ti II.
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| 10. |
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| 11. |
- Hartman, Henrik, et al.
(author)
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The FERRUM Project: Experimental transition probabilities of [Fe II] and astrophysical applications
- 2003
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In: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 397:3, s. 1143-1149
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Journal article (peer-reviewed)abstract
- We report on experimental transition probabilities for thirteenforbidden [Fe II] lines originating from three different metastable FeIi levels. Radiative lifetimes have been measured of two metastablestates by applying a laser probing technique on a stored ion beam.Branching ratios for the radiative decay channels, i.e. M1 and E2transitions, are derived from observed intensity ratios of forbiddenlines in astrophysical spectra and compared with theoretical data. Thelifetimes and branching ratios are combined to derive absolutetransition probabilities, A-values.We present the first experimental lifetime values for the two Fe IIlevels a4G9/2 and b2H11/2and A-values for 13 forbidden transitions froma6S5/2, a4G9/2 andb4D7/2 in the optical region. A discrepancybetween the measured and calculated values of the lifetime for theb2H11/2 level is discussed in terms of levelmixing. We have used the code CIV3 to calculate transitionprobabilities of the a6D-a6S transitions.We have also studied observational branching ratios for lines from 5other metastable Fe II levels and compared them to calculated values. Aconsistency in the deviation between calibrated observational intensityratios and theoretical branching ratios for lines in a wider wavelengthregion supports the use of [Fe II] lines for determination of reddening.
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| 12. |
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| 13. |
- Johansson, Sveneric, et al.
(author)
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The FERRUM Project: New f-value Data for Fe II and Astrophysical Applications
- 2002
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In: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0281-1847 .- 0031-8949 .- 1402-4896. ; T100, s. 71-80
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Conference paper (peer-reviewed)abstract
- We present the FERRUM Project, an international collaboration aiming at a production and evaluation of oscillator strengths (transition probabilities) of selected spectral lines of singly ionized iron group elements, that are of astrophysical relevance. The results obtained include measurements and calculations of permitted and forbidden lines of Fe II. The data have been applied to both emission and absorption lines in astrophysical spectra. We make comparisons between experimental, theoretical and astrophysical f-values. We give a general review of the various measurements, and discuss the UV8 multiplet of Fe II around 1610 Šin detail.
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| 14. |
- Mannervik, S, et al.
(author)
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Lifetime measurements by laser probing in CRYRING - Recent experimental developments
- 2005
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In: Physica Scripta. - 0031-8949 .- 1402-4896. ; T119, s. 49-54
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Journal article (peer-reviewed)abstract
- A laser probing technique for lifetime measurements of long- lived metastable levels has been developed at the ion storage ring CRYRING. The method has been in use for about eight years and it has been applied to various ions. Levels with radiative lifetimes from a few milliseconds up to 28 s have been measured. The method has been continuously developed and this article is focused on recent experimental developments of the method in order to widen its applicability and to increase its efficiency and accuracy.
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| 15. |
- Rostohar, D, et al.
(author)
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Experimental INvestigation of radiative decay rates of metastable levels in Eu II
- 2001
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In: Physica Scripta. - 0031-8949. ; 64, s. 237-237
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Journal article (peer-reviewed)abstract
- The radiative lifetimes of the metastable a 9DJ (J = 2-5) levels in Eu II have been measured by laser probing of a stored ion beam. The lifetimes of all four J levels are slightly above 1 s. A deviation from the expected energy dependence of the decay rates for electric quadrupole transitions is observed and discussed.
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| 16. |
- Rostohar, D, et al.
(author)
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Lifetime measurements of Metastable States in Fe
- 2001
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In: Physical Review Letters. - 1079-7114. ; 86, s. 1466-1466
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Journal article (peer-reviewed)abstract
- The lifetime of two metastable levels in Fe+ has been measured by laser probing of a stored ion beam. In the dense spectrum of Fe+, the metastable levels a 6S5/2 and b 4D7/2 were selected and their lifetimes were determined to be 230+/-30 and 530+/-30 ms, respectively. The lifetimes are compared with previous theoretical results. Metastable lifetime measurements of Fe+ are of great importance for interpretation of spectra from astronomical objects. The present experiment opens for the possibilities to investigate lifetimes of metastable states in complex atomic ions, which have, so far, been unexplored.
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| 17. |
- Rostohar, D, et al.
(author)
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Studies of lifetimes in an ion storage ring using laser technique
- 2003
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In: Hyperfine Interactions. - 1572-9540 .- 0304-3843. ; 146:1-4, s. 151-159
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Conference paper (peer-reviewed)abstract
- The laser-probing method for lifetime measurements of metastable levels, performed by applying the Fast Ion Beam Laser (FIBLAS) method to ions stored in a storage ring, has been developed by the Stockholm group. Recently, we have applied this method to lifetime measurements of close lying metastable levels. In this paper we discuss experimental studies of ions with complex structure and present the first experimentally obtained lifetimes of selected metastable levels in complex systems as Fe+, Eu+ and La+.
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| 18. |
- Schef, P, et al.
(author)
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Lifetimes of metastable levels in Ar II
- 2004
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In: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 29:2, s. 195-199
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Journal article (peer-reviewed)abstract
- We report on a calculation of five lifetimes of metastable levels in Ar II, obtained with a relativistic Hartree-Fock method in which most of the intravalence correlation is represented within a configuration interaction scheme while core-valence correlation is described by a core-polarization model potential with a core-penetration corrective term. The quality of the calculation has been assessed through an experimental determination of the radiative lifetime of the metastable 3d(4)F(9/2) level. The experiment was performed with a laser probing technique on a stored ion beam at the CRYRING of Stockholm.
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| 19. |
- Somesfalean, Gabriel, et al.
(author)
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Violet diode laser in time-resolved stored-ion spectroscopy
- 2004
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In: Physica Scripta. - 0031-8949 .- 1402-4896. ; 69:2, s. 98-103
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Journal article (peer-reviewed)abstract
- Lifetime measurements of the metastable 3d D-2(3/2) level in singly charged calcium were performed using the newly developed violet diode laser operated in an external cavity arrangement. The laser was employed on stored ions at the CRYRING facility to optically pump the resonance line at 397 nm. In combination with laser probing at 866 nm this detection scheme gave the possibility to record the lifetime of this level. which has a radiative lifetime of about 1 s.
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