caa a22 4500 463217276 CHVBK 20180405153201.0 cr unu---uuuuu 170326e20070901xx s 000 0 eng 10.1007/s00269-007-0160-z doi (NATIONALLICENCE)springer-10.1007/s00269-007-0160-z Color centers in topaz: comparison between neutron and gamma irradiation [Elektronische Daten] [K. Krambrock, L. Ribeiro, M. Pinheiro, A. Leal, M. Menezes, J. Spaeth] Neutron- and gamma irradiation-induced paramagnetic centers in natural colorless topaz from four different Brazilian localities were studied by electron paramagnetic resonance (EPR) and optical absorption as a function of irradiation dose and thermal treatment. Gamma irradiation doses were applied up to 1,000kGy with a dose rate of 15kGyh−1. For the neutron irradiation experiments, a neutron flux of 4×1012cm−2s−1 was used with an integrated flux of up to 1×1018cm−2. From the experiments, it is concluded that brownish colors are induced by gamma-rays and may be associated with a single broad isotropic EPR line with g=2.015(2). Both the EPR line and the related optical absorption band at 460nm (2.7eV) are lost during thermal treatments between 150 and 200°C. Fast neutrons create the paramagnetic peroxyl radicals O2 − and the paramagnetic O− hole centers. The O− centers have the same thermal stability as the optical absorption band at 620nm (2.0eV). It is confirmed that the absorption due to the O− center is responsible for the blue color in topaz. Both color centers and their absorption bands are discussed in the context of O− bound small polarons. Springer-Verlag, 2007 Topaz nationallicence Color nationallicence Color enhancement nationallicence Color centers nationallicence EPR nationallicence Irradiation nationallicence Small polaron nationallicence Krambrock K. Departamento de Física, ICEx, Universidade Federal de Minas Gerais, CP. 702, 30.123-970, Belo Horizonte, Minas Gerais, Brazil aut Ribeiro L. Departamento de Física, ICEx, Universidade Federal de Minas Gerais, CP. 702, 30.123-970, Belo Horizonte, Minas Gerais, Brazil aut Pinheiro M. Departamento de Física, ICEx, Universidade Federal de Minas Gerais, CP. 702, 30.123-970, Belo Horizonte, Minas Gerais, Brazil aut Leal A. Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Comissão Nacional de Energia Nuclear (CNEN), Serviço de Reator e Irradiações - TR3, CP. 941, 30.123-970, Belo Horizonte, Minas Gerais, Brazil aut Menezes M. Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Comissão Nacional de Energia Nuclear (CNEN), Serviço de Reator e Irradiações - TR3, CP. 941, 30.123-970, Belo Horizonte, Minas Gerais, Brazil aut Spaeth J. Universität Paderborn, 33098, Paderborn, Germany aut Physics and Chemistry of Minerals Springer-Verlag 34/7(2007-09-01), 437-444 0342-1791 34:7<437 2007 34 269 https://doi.org/10.1007/s00269-007-0160-z text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00269-007-0160-z text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Krambrock K. Departamento de Física, ICEx, Universidade Federal de Minas Gerais, CP. 702, 30.123-970, Belo Horizonte, Minas Gerais, Brazil aut NATIONALLICENCE 700 1- Ribeiro L. Departamento de Física, ICEx, Universidade Federal de Minas Gerais, CP. 702, 30.123-970, Belo Horizonte, Minas Gerais, Brazil aut NATIONALLICENCE 700 1- Pinheiro M. Departamento de Física, ICEx, Universidade Federal de Minas Gerais, CP. 702, 30.123-970, Belo Horizonte, Minas Gerais, Brazil aut NATIONALLICENCE 700 1- Leal A. Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Comissão Nacional de Energia Nuclear (CNEN), Serviço de Reator e Irradiações - TR3, CP. 941, 30.123-970, Belo Horizonte, Minas Gerais, Brazil aut NATIONALLICENCE 700 1- Menezes M. Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Comissão Nacional de Energia Nuclear (CNEN), Serviço de Reator e Irradiações - TR3, CP. 941, 30.123-970, Belo Horizonte, Minas Gerais, Brazil aut NATIONALLICENCE 700 1- Spaeth J. Universität Paderborn, 33098, Paderborn, Germany aut NATIONALLICENCE 773 0- Physics and Chemistry of Minerals Springer-Verlag 34/7(2007-09-01), 437-444 0342-1791 34:7<437 2007 34 269 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer