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Doctoral Thesis
DOI
10.11606/T.43.1993.tde-23082013-141347
Document
Author
Full name
Eduardo di Mauro
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1993
Supervisor
Committee
Sano, Walter (President)
Amaral, Lia Queiroz do
Barberis, Gaston Eduardo
Leite, Jose Roberto
Nascimento, Otaciro Rangel
Title in Portuguese
Centros paramagnéticos do NH4Br:Cu2+
Keywords in Portuguese
Centros paramagnéticos
Matéria condensada
Reações nucleares
Ressonância paramagnética eletrônica
Abstract in Portuguese
Com o objetivo de entendermos como as duas transições de fase, abaixo da temperatura ambiente, modificam o comportamento dos centros paramagnéticos formados em torno do Cu2+, estudamos o NH4BR:Cu2+ crescido em soluções cujo pH variou de zero a 8,26. Utilizando principalmente, a RPE nas bandas X e Q, realizamos um estudo térmico e angular desde 77 K à temperatura ambiente, com o qua1 verificamos que o NH4BR:Cu2+ forma três centros paramagnéticos distintos, de acordo com o pH das soluções, sendo um deles descrito pela primeira vez. Pelas simetrias apresentadas para cada uma das fases do cristal, pudemos propor modelos para estes centros compatíveis com as transições de fase. Mostramos que em virtude da forte covalência apresentada pelos centros, a interação superhiperfina supera a hiperfina.
Title in English
Paramagnetic centers of NH4Br:Cu2+
Keywords in English
Condensed matter
Electron paramagnetic resonance
Nuclear reactions
Paramagnetic centers
Abstract in English
In order to understand how the two phase transitions, below the room temperature, change the behavior of the paramagnetic centres formed around the Cu2+, we have been studying the NH4Br:Cu2+, grown in solutions with pH varying from zero to 8.26. Using mainly EPR at X and Q bands, we performed a thermal and angular study from 77 K to room temperature. We verified that the NH4Br:Cu2+ forms three distinct paramagnetic centres depending on the pH of the solution, one of them we described for the first time. According to the symmetries of each phase, satisfactory models have been proposed for these centres. As a result of the strong covalency exhibited by Cu2+ and its neighbourhood, we have shown that the superhyperfine interaction is greater than the hyperfine one.
 
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40515DiMauro.pdf (39.12 Mbytes)
Publishing Date
2013-08-26
 
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