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The FERRUM project: Transition probabilities for forbidden lines in [Fe II] and experimental metastable lifetimes
Stockholm University, Faculty of Science, Department of Physics.
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2009 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 508, no 1, 525-529 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2009. Vol. 508, no 1, 525-529 p.
Keyword [en]
atomic data, methods: laboratory, techniques: spectroscopic, stars: individual: Eta Carinae
National Category
Atom and Molecular Physics and Optics Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-32215DOI: 10.1051/0004-6361/200913233ISI: 000272417700054OAI: oai:DiVA.org:su-32215DiVA: diva2:279810
Available from: 2009-12-07 Created: 2009-12-07 Last updated: 2017-12-12Bibliographically approved
In thesis
1. High Resolution Spectroscopy of Singly Charged Ions: Applications of Laser and Fourier Transform Techniques
Open this publication in new window or tab >>High Resolution Spectroscopy of Singly Charged Ions: Applications of Laser and Fourier Transform Techniques
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2010. 99 p.
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-42627 (URN)978-91-7447-134-2 (ISBN)
Public defence
2010-10-22, FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2010-09-30 Created: 2010-09-10 Last updated: 2010-10-01Bibliographically approved
2. LIfetimes measurement states in ions at an ion storage ring
Open this publication in new window or tab >>LIfetimes measurement states in ions at an ion storage ring
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholms universitet, Fysikum, 2011
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:su:diva-67024 (URN)
Available from: 2011-12-22 Created: 2011-12-22 Last updated: 2011-12-22Bibliographically approved
3. Time-Resolved Spectroscopy and Intensity Measurements of Singly Charged Ions
Open this publication in new window or tab >>Time-Resolved Spectroscopy and Intensity Measurements of Singly Charged Ions
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is mainly concerned with investigations of spontaneous radiatively decaying states in both negative and positive singly charged ions. When possible, the measured lifetime of the state has been combined with branching fractions in order to derive the absolute transition probability (A-value) between different quantum states. The radiative transition probability between two quantum states is a fundamental atomic property. Knowledge of this property can be used as a diagnostic tool in, for example, abundance and temperature determinations with applications in many fields, e.g. astronomy, plasma physics, atomic physics etc.

The focus of the experiments has been on lifetime measurements of long-lived metastable states. Lifetimes of long-lived metastable states are interesting in both theoretical aspects as well as the challenge it poses to the experimentalist. To perform such experiments, impact from the surrounding environment on the stored ions has to be kept to a minimum for extended periods of time. The metastable lifetimes presented here have been measured with time-resolved laser spectroscopic techniques in two different types of ion storage rings. One of them is a new type of unique cryogenically cooled storage ring made of purely electrostatic ion optical elements. As is demonstrated in this thesis, this device opens up a completely new time domain where lifetime measurements now can be performed. In addition, this thesis includes a discussion and preliminary studies of weak interactions otherwise limited by magnetic fields and/or thermal radiation from the environment. When available, the results have been compared to previous measurements and theoretical calculations which enables an evaluation of different methods and theoretical models.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2015. 88 p.
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-113503 (URN)978-91-7649-100-3 (ISBN)
Public defence
2015-03-20, sal FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 6: Accepted.

Available from: 2015-02-26 Created: 2015-02-03 Last updated: 2015-02-26Bibliographically approved

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