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Ruthenium Ra Z = 44

This element was discovered by A. Sniadecki in Vilno (then in Russia) in 1808 and was rediscovered by Osann in 1828 and by Klaus in 1844. Its name comes from Ruthenia (Russia).

Ionization energies
RuI 7.4 eV, RuII 16.8 eV, RuIII 28.5 eV.

Absorption lines of RuI

Table 1. Equivalent width of RuI 4081(7)
Group V
S 0.005
K5 0.044

Absorption lines of RuII
In the sun, RuII 3177(2) has W = 0.014.

Both RuI and RuII are present in the spectra of late type stars. Orlov and Shavrina (1990) have reported observations in G- and K-type giants.

Behavior in non-normal stars
Ru I was detected by Jaschek and Brandi (1972) in at least one Ap star of the Cr-Eu-Sr subgroup. Leckrone et al. (199lb) detected RuII in one star of the Hg-Mn subgroup.

Ru is perhaps enhanced in Ba stars (Warner 1965, Lambert 1985).

Ru is enhanced in subgiant CH stars (Krishnaswamy and Sneden 1985) and in S-type stars (Smith and Wallerstein 1983), leading to an overabundance by one order of magnitude.

Isotopes
Ru has seven stable isotopes, namely Ru 96, 98, 99, 100, 101, 102 and 104, which occur in the solar system with respective frequencies 5%, 2%, 13%, 13%, 17%, 31% and 19%. There exist also nine short-lived isotopes.

Origin
Ru96 and Ru98 are pure p process products, Ru100 is produced by the s process and Ru104 by the r process. Ru 99, 101 and 102 can be produced by both the r process and the s process.


Published in "The Behavior of Chemical Elements in Stars", Carlos Jaschek and Mercedes Jaschek, 1995, Cambridge University Press.

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