| 1. |
- Johansson, Sveneric, et al.
(författare)
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The FERRUM Project: New f-value Data for Fe II and Astrophysical Applications
- 2002
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Ingår i: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0281-1847 .- 0031-8949 .- 1402-4896. ; T100, s. 71-80
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Konferensbidrag (refereegranskat)abstract
- We present the FERRUM Project, an international collaboration aiming at a production and evaluation of oscillator strengths (transition probabilities) of selected spectral lines of singly ionized iron group elements, that are of astrophysical relevance. The results obtained include measurements and calculations of permitted and forbidden lines of Fe II. The data have been applied to both emission and absorption lines in astrophysical spectra. We make comparisons between experimental, theoretical and astrophysical f-values. We give a general review of the various measurements, and discuss the UV8 multiplet of Fe II around 1610 Šin detail.
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| 2. |
- Någård, M. B., et al.
(författare)
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Dissociative recombination of D+(D2O)(2) water cluster ions with free electrons
- 2002
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 117:11, s. 5264-5270
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Tidskriftsartikel (refereegranskat)abstract
- Dissociative recombination (DR) of the water cluster ion D+(D2O)(2) has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). Cluster ions were injected into the ring and accelerated to an energy of 2.28 MeV. The stored ion beam was merged with an almost monoenergetic electron beam, and neutral fragments produced by DR were detected by an energy-sensitive surface barrier detector. The first experimental determinations of the absolute DR cross section and branching ratios for a cluster ion are reported. The cross section for the process D+(D2O)(2)+e(-) is large and reaches 6.10(-12) cm(2) at a low center-of-mass collision energy of 0.001 eV. The cross section has an E-1.19+/-0.02 dependence in the energy range 0.001-0.0052 eV, and a steeper slope with an E-1.70+/-0.12 dependence for E=0.052-0.324 eV. The general trends are similar to the results for previously studied molecular ions, but the cross section is higher in absolute numbers for the cluster ion. Thermal rate coefficients for electron temperatures of 50-2000 K are deduced from the cross section data and the rate coefficients are consequently also large. Branching ratios for the product channels are determined with a grid technique. Break-up into 2D(2)O+D is the dominating dissociation channel with a probability of 0.94+/-0.04. The channel resulting in the fragments D2O+OD+D-2 has a probability of 0.04+/-0.02, and the probability for formation of D3O+D2O is 0.02+/-0.03. The results are compared with data for molecular ions, and the cluster dissociation dynamics are discussed.
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