This element was discovered in 1879 in Paris by P. Lecoq de Boisbaudran. Its name alludes to the mineral Samarskite, named after a Russian mine official, Colonel Samarski.

Ionization energies
SmI 5.6 eV, SmII 11.0 eV, SmIII 23.4 eV, SmIV 41.4 eV.

Absorption lines of SmII

Table 1. Equivalent widths of SmII

  4566(32)   4719(3)   6731(59)

Group V III V III Ib

F5 0.003   0.003    
G0         0.061
G2     0.007    
K0   0.062   0.026  
K1         0.116
K2       0.046  
K5 0.026        
M2         0.l00(Ia)

Sm II lines are visible from F 5 onwards and strengthen monotonically. Gopka et al. (1990) have observed SmII lines in giants K 5 and M 0.

Behavior in non-normal stars
SmII lines are observed in the spectra of many Ap stars of the Cr-Eu-Sr subgroup. Aikman et al. (1979) also observed SmIII lines in the spectra of some stars of this subgroup. SmII and SmIII are also present in one Bp star of the Si subgroup (Cowley and Crosswhite 1978).

SmII lines are enhanced in the spectra of Am stars (Smith 1973, 1974). The W values are larger by factors of 2-3 than in normal stars of the same temperature.

Sm lines are enhanced in some Ba stars, which leads to large overabundances (Lambert 1985). However, this element is not observed in all Ba stars. Typically W(4566) = 0.081 for a KOIII Ba star (Danziger 1965).

Sm lines are enhanced in many C stars cooler than C 3 (Utsumi 1966, 1984).

Numerous Sm II lines have been observed in at least one S-type star (Bidelman 1953). Sm is enhanced in SC stars (Kipper and Wallerstein 1990).

SmII lines have been observed by Gilroy et al. (1988) in the spectra of metal-weak G and K dwarfs. These authors find the element to be overabundant with respect to iron (see also Part Two, section 2.2).

Sm is enhanced in Magellanic Cloud stars (Luck and Lambert 1992).

Sm has seven stable isotopes and isomers, Sm 144, 147, 148, 149, 150, 152 and 154, which occur in the solar system with frequencies of 3%, 15%, 11%, 14%, 7%,27 % and 23 % respectively. There exist also ten short-lived isotopes, among which is Sm146 with a half life of 7 × 107 years. Sm146 can be used for radioactive dating.

Sm144 is a pure p process product, Sm148 and Sm150 are pure s process products and Sm154 is a pure r process product. Sm 147, 149 and 152 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.