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The FERRUM project: Experimental transition probabilities from highly excited even 5s levels in Cr II
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2014 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 570, A34- p.Article in journal (Refereed) Published
Abstract [en]

We report lifetime measurements of the five levels in the 3d(4)(a(5)D)5s e(6)D term in Cr II at an energy around 83 000 cm(-1), and log(gf) values for 38 transitions from the investigated levels. The lifetimes are obtained using time-resolved, laser-induced fluorescence on ions from a laser-produced plasma. Since the levels have the same parity as the low-lying states directly populated in the plasma, we used a two-photon excitation scheme. This process is greatly facilitated by the presence of the 3d(4)(a(5)D)4p z(6)F levels at roughly half the energy difference. The f-values are obtained by combining the experimental lifetimes with branching fractions derived using relative intensities from a hollow cathode lamp recorded with a Fourier transform spectrometer.

Place, publisher, year, edition, pages
2014. Vol. 570, A34- p.
Keyword [en]
atomic data, methods: laboratory: atomic, techniques: spectroscopic
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-110200DOI: 10.1051/0004-6361/201424762ISI: 000344158500140OAI: oai:DiVA.org:su-110200DiVA: diva2:769959
Note

AuthorCount:5;

Available from: 2014-12-09 Created: 2014-12-08 Last updated: 2017-12-05Bibliographically approved
In thesis
1. 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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