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Laser Spectroscopic Investigations of Decay Properties in Stored Ions
Stockholm University, Faculty of Science, Department of Physics.
Responsible organisation
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Investigations and measurements of metastable states are in many ways very important. Spectroscopists, theorists and astrophysicists have all great interest and requirements regarding knowledge about such states and their properties. One of the interesting properties is the lifetime of each state and lifetime measurements are therefore of great importance. It is necessary to have a long observation time when performing investigations on metastable states in ions and there are some different methods to fulfill this requirement. One method to store ions is to use an ion storage ring in which the ions are bent in circle by a magnetic or an electrostatic field. The storage ring method combined with a laser probing technique constitutes the basis for the papers described in this thesis. The thesis also contains some theoretical background to the experiments together with explanations regarding the experimental setup, the procedure for the laser probing technique and the systematic effects that have to be considered. The thesis includes results from nine different positive and negative singly charged ions. The experimental and theoretical results are presented and compared.

The experiments have been done in collaboration with E. Biémont's theoretical group in Belgium, with S. Johansson's astrophysical group in Lund and D. Hanstorp's group in Gothenburg.

Place, publisher, year, edition, pages
Stockholm: Fysikum , 2008. , 221 p.
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-7768ISBN: 978-91-7155-680-6 (print)OAI: oai:DiVA.org:su-7768DiVA: diva2:199022
Public defence
2008-06-17, sal FD5, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Available from: 2008-05-27 Created: 2008-05-20 Last updated: 2010-09-14Bibliographically approved
List of papers
1. Importance of an M2 Depopulating Channel for a Kr II Metastable State
Open this publication in new window or tab >>Importance of an M2 Depopulating Channel for a Kr II Metastable State
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2004 In: Physical Review Letters, Vol. 93, 063003- p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25154 (URN)
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20Bibliographically approved
2. Disentanglement of magnetic field mixing reveals the spontaneous M2 decay rate for a metastable level in Xe+
Open this publication in new window or tab >>Disentanglement of magnetic field mixing reveals the spontaneous M2 decay rate for a metastable level in Xe+
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2005 In: Physical Review A, Vol. 72, 020501- p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25155 (URN)
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20Bibliographically approved
3. Inclusion of Electric Octupole Contributions Explains the Fast Radiative Decays of Two Metastable States in Ar+
Open this publication in new window or tab >>Inclusion of Electric Octupole Contributions Explains the Fast Radiative Decays of Two Metastable States in Ar+
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2007 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 99, 213001- p.Article in journal (Refereed) Published
Abstract [en]

A laser probing investigation has yielded the lifetimes of the 3s23p4(1D)3d 2G7/2,9/2 metastable doublet states of Ar+. The results, obtained with the CRYRING ion storage ring of Stockholm, are 3.0±0.4 and 2.1±0.1  s, respectively. Comparisons with theoretical values calculated with two independent theoretical approaches, i.e., the pseudorelativistic Hartree-Fock method and the multiconfiguration Breit-Pauli approach, have allowed us to establish the unexpected and extraordinary strong contribution of an electric octupole (E3) transition to the ground state, in addition to the M1 decay channels to the 3d 2,4F states and the E2 contributions to the 4s 2P, 2D states.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-12437 (URN)10.1103/PhysRevLett.99.213001 (DOI)000251107500017 ()
Available from: 2008-01-15 Created: 2008-01-15 Last updated: 2017-12-13Bibliographically approved
4. The FERRUM project: an extremely long radiative lifetime in Ti II measured in an ion storage ring
Open this publication in new window or tab >>The FERRUM project: an extremely long radiative lifetime in Ti II measured in an ion storage ring
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2003 In: J. Phys. B: At. Mol. Opt. Phys, Vol. 36, L197-L202 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25157 (URN)
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20Bibliographically approved
5. The FERRUM project: experimentally determined metastable lifetimes and transition probabilities for forbidden [Ti II] lines observed in Eta Carinae
Open this publication in new window or tab >>The FERRUM project: experimentally determined metastable lifetimes and transition probabilities for forbidden [Ti II] lines observed in Eta Carinae
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2005 In: Mon. Not. R. Astron. Soc., Vol. 361, 206-210 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25158 (URN)
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20Bibliographically approved
6. Experimental Oscillator Strengths for Forbidden Lines in Complex Spectra
Open this publication in new window or tab >>Experimental Oscillator Strengths for Forbidden Lines in Complex Spectra
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2005 In: Physica Scripta, Vol. T119, 40-44 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25159 (URN)
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20Bibliographically approved
7. The FERRUM project: Experimental and theoretical transition rates of forbidden [Sc II] lines and radiative lifetimes of metastable Sc II levels
Open this publication in new window or tab >>The FERRUM project: Experimental and theoretical transition rates of forbidden [Sc II] lines and radiative lifetimes of metastable Sc II levels
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2008 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 480, no 2, 575-580 p.Article in journal (Refereed) Published
Abstract [en]

Context. In many plasmas, long-lived metastable atomic levels are depopulated by collisions (quenched) before they decay radiatively. In low-density regions, however, the low collision rate may allow depopulation by electric dipole (E1) forbidden radiative transitions, so-called forbidden lines (mainly M1 and E2 transitions). If the atomic transition data are known, these lines are indicators of physical plasma conditions and used for abundance determination.

Aims. Transition rates can be derived by combining relative intensities between the decay channels, so-called branching fractions (BFs), and the radiative lifetime of the common upper level. We use this approach for forbidden [Sc II] lines, along with new calculations.

Methods. Neither BFs for forbidden lines, nor lifetimes of metastable levels, are easily measured in a laboratory. Therefore, astrophysical BFs measured in Space Telescope Imaging Spectrograph (STIS) spectra of the strontium filament of Eta Carinae are combined with lifetime measurements using a laser probing technique on a stored ion-beam (CRYRING facility, MSL, Stockholm). These quantities are used to derive the absolute transition rates (A-values). New theoretical transition rates and lifetimes are calulated using the CIV3 code.

Results. We report experimental lifetimes of the Sc II levels 3d2 a3P0,1,2 with lifetimes 1.28, 1.42, and 1.24 s, respectively, and transition rates for lines from these levels down to 3d4s a3D in the region 8270-8390 Å. These are the most important forbidden [Sc II] transitions. New calculations for lines and metastable lifetimes are also presented, and are in good agreement with the experimental data.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-14409 (URN)10.1051/0004-6361:20079057 (DOI)000253806700034 ()
Available from: 2008-10-03 Created: 2008-10-03 Last updated: 2017-12-13Bibliographically approved
8. Laser-probing measurements and calculations of lifetimes of the 5d 2D3/2 and 5d 2D5/2 metastable levels in Ba II
Open this publication in new window or tab >>Laser-probing measurements and calculations of lifetimes of the 5d 2D3/2 and 5d 2D5/2 metastable levels in Ba II
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2007 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, no 5, 052506- p.Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-25161 (URN)10.1103/PhysRevA.75.052506 (DOI)000246890400083 ()
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20 Last updated: 2017-12-13Bibliographically approved
9. Monitoring the weak collisional excitation of a stored ion beam reveals the radiative decay rate of extremely long-lived metastable levels
Open this publication in new window or tab >>Monitoring the weak collisional excitation of a stored ion beam reveals the radiative decay rate of extremely long-lived metastable levels
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2007 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 76, no 3, 030502- p.Article in journal (Refereed) Published
Abstract [en]

A fast ion beam stored in an ion storage ring will suffer from collisional interaction with the residual gas even in extreme ultrahigh vacuum. Normally these effects are negligible or easy to correct for. For measurements of extremely long radiative lifetimes of metastable levels we have found that correction for collisional effects is very important and usually limits the accuracy. We now suggest that by monitoring the process of collisional excitation of the metastable level of interest the lifetime value could be determined directly with improved accuracy. The method is applied to available data from our recent measurement of the 5d 2D5∕2 level in Ba+, yielding a value of 32.0±2.9 s, thus squeezing the error bar by 35%.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-25162 (URN)10.1103/PhysRevA.76.030502 (DOI)000249786000010 ()
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20 Last updated: 2017-12-13Bibliographically approved
10. Metastable levels in ScII: Lifetime measurements and calculations
Open this publication in new window or tab >>Metastable levels in ScII: Lifetime measurements and calculations
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2008 (Swedish)In: Physica scripta. T, ISSN 0281-1847, Vol. 78, no 1, 015301- p.Article in journal (Refereed) Published
Abstract [en]

The lifetime of the metastable level 3d2 1G4 in a singly charged scandium has been experimentally investigated at the ion storage ring CRYRING. A laser probing technique has been used for the studies. We also report calculated lifetimes and transition rates for 10 metastable levels in Sc II, including the 3d2 1G4 state, by calculations using configuration interaction wave functions. The lifetime of the 1G4 level is experimentally determined to be τexp=2.64±0.18 s and is in good agreement with the theoretical calculation τth=2.84 s.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-14528 (URN)10.1088/0031-8949/78/01/015301 (DOI)000258143600018 ()
Available from: 2008-10-03 Created: 2008-10-03 Last updated: 2017-12-13Bibliographically approved
11. Lifetimes of metastable levels of singly ionized titanium : theory and experiment
Open this publication in new window or tab >>Lifetimes of metastable levels of singly ionized titanium : theory and experiment
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2008 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 41, no 12Article in journal (Refereed) Published
Abstract [en]

This paper presents new theoretical lifetimes of metastable levels in singly ionized titanium, Ti II. Along with the lifetimes, transition probabilities for several decay channels from these metastable levels are presented. The calculations are supported by experimental lifetime determinations of the 3d3 b 2D5/2 and 3d2(3P)4s b 2P3/2 levels along with revised values of the previously published lifetimes of the 3d2(3P)4s b 4P5/2 and 3d2(3P)4s b 2P1/2 levels originating partly from a reanalysis utilizing a recently developed method applied on the previously recorded data and partly from new measurements. The presented theoretical investigation of lifetimes of metastable levels in Ti II shows that the HFR calculations are in general compatible with measurements performed using the ion storage ring CRYRING of Stockholm University. The transition probabilities of forbidden lines derived from the new lifetime values will be useful for the diagnostics of low density laboratory or astrophysical plasmas, particularly those encountered in the strontium filament found in the ejecta of η Carinae.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-25164 (URN)10.1088/0953-4075/41/12/125703 (DOI)000257177700017 ()
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20 Last updated: 2017-12-13Bibliographically approved
12. Radiative Lifetime of a Bound Excited State of Te-
Open this publication in new window or tab >>Radiative Lifetime of a Bound Excited State of Te-
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2004 (English)In: Physical Review Letters, ISSN 0031-9007, Vol. 92, no 25, 253002- p.Article in journal (Refereed) Published
Abstract [en]

We report on the first experimental study of the lifetime of a bound excited state of a negative ion. A new experimental technique was developed and used to measure the radiative lifetime of the 5p52P1/2 level of Te-. The experiment was performed in a magnetic storage ring, where a laser beam was applied along one of the straight sections. In the experiment the population of the excited J=1/2 level was probed each time the Te- ions passed through the laser field. A decay curve was built up by sampling the population of the excited level of the Te- ions as a function of time after injection into the ring. A multiconfiguration Dirac-Hartree-Fock calculation was performed in conjunction with the experiment. The calculation yielded a radiative lifetime of 0.45 s, in excellent agreement with the measured value of 0.42(5) s.

Identifiers
urn:nbn:se:su:diva-25165 (URN)10.1103/PhysRevLett.92.253002 (DOI)
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20 Last updated: 2010-10-21Bibliographically approved
13. Radiative lifetimes of metastable states of negative ions
Open this publication in new window or tab >>Radiative lifetimes of metastable states of negative ions
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2006 In: Physical Review A, Vol. 73, 032705- p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25166 (URN)
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20Bibliographically approved

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