A theoretical study of the absorption spectra of Pb+ and Pb3+ in site K+ of microcline: application to the color of amazonite |
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| Authors: | A Julg |
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| Institution: | (1) Laboratoire de Chimie Théorique (associé au CRMC2-CNRS, LP 7251), Université de Provence, Place Victor Hugo, F-13331 Marseille Cedex 3, France, FR |
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| Abstract: | The blue-green color of amazonite has been assigned by various authors to ions Pb+ (6 s)2 (6 p) and/or Pb3+ (6 s) in site of K+ of microcline. Owing to the complex which forms between the ion Pb3+ and the lone pairs of the oxygen atoms surrounding it, the peripheral electron of Pb3+ passes on the levels (6 p) of the latter, which results in a great similarity of the spectra of Pb+ and Pb3+ in amazonite (the transition energies are multiplied by a factor greater than 1), whereas, in the isolated state, these spectra
are completely different from one another. An analytical development of the crystal field around a site K+ is established. Under the effect of the crystal field, the transition 2
P
1/2→2
P
3/2 (6 p) is split into two double transitions. The lower transition only falls in the visible domain (1.6–1.8 eV for Pb+), the second in U−V. The green color would arise from the ion Pb+, whereas the blue one would be attributed to the ion Pb3+.
Received: 23 January 1997 / Revised, accepted: 10 September 1997 |
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