Open AccessThe FERRUM project: metastable lifetimes in Cr ii
Author(s) -
Bäckström E.,
Gurell J.,
Royen P.,
Mannervik S.,
Norlin L.,
BlackwellWhitehead R.,
Hartman H.,
Nilsson H.
Publication year - 2012
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2011.20152.x
Subject(s) - physics , metastability , radiative transfer , atomic physics , plasma , ion , ionization , spectral line , chromium , context (archaeology) , storage ring , parity (physics) , laser , nuclear physics , optics , quantum mechanics , paleontology , beam (structure) , chemistry , organic chemistry , biology
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 d 4 (a 3 D)4 s c 4 D 5/2 and 3 d 4 (a 3 D)4 s c 4 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 τ 5/2 = 1.28(16) s and τ 7/2 = 1.37(7) s, respectively. A comparison with previous theoretical work shows good agreement and the result is discussed in a theoretical context.