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New laboratory lifetime measurements of U II for the uranium cosmochronometer

Lundberg, Hans LU ; Johansson, Sveneric LU ; Nilsson, Hampus LU and Zhang, Z (2001) In Astronomy & Astrophysics 372(3). p.50-52
Abstract
We present new measurements of radiative lifetimes for six energy levelsof singly ionized uranium, U II, using laser-induced fluorescencetechnique. One of the levels,5f<SUP>3</SUP>6d7p<SUP>6</SUP>M<SUB>13/2</SUB> at 26191 cm<SUP>-1</SUP>,decays by a transition at 3859.6 Å. This line has recently beenobserved in the spectrum of the metal-poor star CS1082-001, the firstdetection of uranium outside the solar system. The lambda 3859 line canbe used as the presently most accurate cosmochronometer (Cayrel et al.cite{Cayrel}). Our value of the lifetime of the<SUP>6</SUP>M<SUB>13/2</SUB> level is 18.6+/-0.7 ns, and it confirms thef-value used in the Nature article by Cayrel et... (More)
We present new measurements of radiative lifetimes for six energy levelsof singly ionized uranium, U II, using laser-induced fluorescencetechnique. One of the levels,5f<SUP>3</SUP>6d7p<SUP>6</SUP>M<SUB>13/2</SUB> at 26191 cm<SUP>-1</SUP>,decays by a transition at 3859.6 Å. This line has recently beenobserved in the spectrum of the metal-poor star CS1082-001, the firstdetection of uranium outside the solar system. The lambda 3859 line canbe used as the presently most accurate cosmochronometer (Cayrel et al.cite{Cayrel}). Our value of the lifetime of the<SUP>6</SUP>M<SUB>13/2</SUB> level is 18.6+/-0.7 ns, and it confirms thef-value used in the Nature article by Cayrel et al. (cite{Cayrel}),which is based on an experimental lifetime of 20+/-5 ns (Chen &Borzileri cite{Chen}). The new measurement also removes the doubt aboutthe choice between that value and other f-values in the literature,differing by a factor of 3. Adopting the same branching fraction as Chen& Borzileri (cite{Chen}) for the 3859.6 Å line, we derive agf-value of 0.68, which is 8% higher than the value used by Cayrel etal. (cite{Cayrel}). Of significance for the chronometer is also thereduced uncertainty of the radiative lifetime, 4% compared to 25%, andconsequently of the f-value, which should decrease the uncertainty inthe determination of the stellar age considerably. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
STARS: EVOLUTION, ATOMIC DATA, GALAXY: EVOLUTION
in
Astronomy & Astrophysics
volume
372
issue
3
pages
50 - 52
publisher
EDP Sciences
external identifiers
  • scopus:0035373198
ISSN
0004-6361
DOI
10.1051/0004-6361:20010608
language
English
LU publication?
yes
id
6e0bbaf6-d062-4b7f-85a4-04361db4e372 (old id 130188)
date added to LUP
2007-07-13 14:04:51
date last changed
2018-01-07 08:51:54
@article{6e0bbaf6-d062-4b7f-85a4-04361db4e372,
  abstract     = {We present new measurements of radiative lifetimes for six energy levelsof singly ionized uranium, U II, using laser-induced fluorescencetechnique. One of the levels,5f&lt;SUP&gt;3&lt;/SUP&gt;6d7p&lt;SUP&gt;6&lt;/SUP&gt;M&lt;SUB&gt;13/2&lt;/SUB&gt; at 26191 cm&lt;SUP&gt;-1&lt;/SUP&gt;,decays by a transition at 3859.6 Å. This line has recently beenobserved in the spectrum of the metal-poor star CS1082-001, the firstdetection of uranium outside the solar system. The lambda 3859 line canbe used as the presently most accurate cosmochronometer (Cayrel et al.cite{Cayrel}). Our value of the lifetime of the&lt;SUP&gt;6&lt;/SUP&gt;M&lt;SUB&gt;13/2&lt;/SUB&gt; level is 18.6+/-0.7 ns, and it confirms thef-value used in the Nature article by Cayrel et al. (cite{Cayrel}),which is based on an experimental lifetime of 20+/-5 ns (Chen &amp;Borzileri cite{Chen}). The new measurement also removes the doubt aboutthe choice between that value and other f-values in the literature,differing by a factor of 3. Adopting the same branching fraction as Chen&amp; Borzileri (cite{Chen}) for the 3859.6 Å line, we derive agf-value of 0.68, which is 8% higher than the value used by Cayrel etal. (cite{Cayrel}). Of significance for the chronometer is also thereduced uncertainty of the radiative lifetime, 4% compared to 25%, andconsequently of the f-value, which should decrease the uncertainty inthe determination of the stellar age considerably.},
  author       = {Lundberg, Hans and Johansson, Sveneric and Nilsson, Hampus and Zhang, Z},
  issn         = {0004-6361},
  keyword      = {STARS: EVOLUTION,ATOMIC DATA,GALAXY: EVOLUTION},
  language     = {eng},
  number       = {3},
  pages        = {50--52},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {New laboratory lifetime measurements of U II for the uranium cosmochronometer},
  url          = {http://dx.doi.org/10.1051/0004-6361:20010608},
  volume       = {372},
  year         = {2001},
}