Journal Article

The FERRUM project: metastable lifetimes in Cr <span class="smallCaps">ii</span>

E. Bäckström, J. Gurell, P. Royen, S. Mannervik, L. Norlin, R. Blackwell-Whitehead, H. Hartman and H. Nilsson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 420, issue 2, pages 1636-1639
Published in print February 2012 | ISSN: 0035-8711
Published online January 2012 | e-ISSN: 1365-2966 | DOI:
The FERRUM project: metastable lifetimes in Cr ii

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Parity forbidden radiative transitions from metastable levels are observed in spectra of low-density astrophysical plasmas. These lines are used as probes of the physical conditions, made possible due to the long lifetime of their upper level. In a joint effort, the FERRUM project aims to obtain new and accurate atomic data for the iron-group elements, and part of this project concerns forbidden lines. The radiative lifetimes of the metastable energy levels 3 d4(a 3 D)4 s   c4 D 5/2 and 3 d4(a 3 D)4 s   c4 D 7/2 of singly ionized chromium have been measured. The experiment has been performed at the ion storage ring CRYRING. We employed a laser-probing technique developed for measuring long lifetimes. In this article, we present the lifetimes of these levels to be τ5/2= 1.28(16) s and τ7/2= 1.37(7) s, respectively. A comparison with previous theoretical work shows good agreement and the result is discussed in a theoretical context.

Keywords: atomic data; methods: laboratory; techniques: spectroscopic; astronomical data bases: miscellaneous

Journal Article.  2288 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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