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Monitoring the weak collisional excitation of a stored ion beam reveals the radiative decay rate of extremely long-lived metastable levels
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
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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%.

Place, publisher, year, edition, pages
2007. Vol. 76, no 3, 030502- p.
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-25162DOI: 10.1103/PhysRevA.76.030502ISI: 000249786000010OAI: oai:DiVA.org:su-25162DiVA: diva2:199017
Note
Part of urn:nbn:se:su:diva-7768Available from: 2008-05-27 Created: 2008-05-20 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Laser Spectroscopic Investigations of Decay Properties in Stored Ions
Open this publication in new window or tab >>Laser Spectroscopic Investigations of Decay Properties in Stored Ions
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:nbn:se:su:diva-7768 (URN)978-91-7155-680-6 (ISBN)
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
2. Laboratory studies of forbidden decay processes in stored ions
Open this publication in new window or tab >>Laboratory studies of forbidden decay processes in stored ions
2008 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2008. 61 p.
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-30244 (URN)
Presentation
2008-01-30, FA31, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 14:00 (English)
Opponent
Supervisors
Available from: 2010-09-14 Created: 2009-10-07 Last updated: 2010-09-14Bibliographically approved
3. 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

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