This element was discovered by B. Courtois in Paris in 1811. Its name comes from the Greek iodes (violet).
II 10.4 eV, III 19.1 eV, IIII 33.2 eV.
No I line is observed in the sun. Ionized iodine was found in one Ap star of the Cr-Eu-Sr subgroup by Jaschek and Brandi (1972).
I occurs in the form of I127. There exist a long-lived isotope, I129, with a half life of 1.7 × 107 years and 22 short-lived isotopes and isomers. I129 in principle could be used for radioactive dating.
I is an r process element.
Published in "The Behavior of Chemical Elements in Stars", Carlos Jaschek and Mercedes Jaschek, 1995, Cambridge University Press.