Evidence of the participation of electronic excited states in the mechanism of positronium formation in substitutional Tb(1-x)Eu(x)(dpm)3 solid solutions studied by optical and positron annihilation spectroscopies.
Positronium formation in the bimary molecular solid solutions Tb(1-x)Eu(x) (dpm)(3) (dpm = dipivaloylmethanate) has been investigated. A strong linear correlation between the (5)D(4) Tb(iii) energy level excited state lifetime and the positronium formation probability has been observed. This correlation indicates that the ligand-to-metal charge transfer LMCT states act in both luminescence quenching and positronium formation inhibition, as previously proposed. A kinetic mechanism is proposed to explain this correlation and shows that excited electronic states have a very important role in the positronium formation mechanism.
Laboratório de Espectroscopia de Aniquilação de Pósitrons, Departamento de Química, ICEx, Universidade Federal de Minas Gerais-UFMG, C. P. 702, CEP 31270-901 Belo Horizonte, MG, Brazil.
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Fulgêncio
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de Oliveira
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Windmöller
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Brito
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Malta
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de Sá
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Magalhães
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