Navegando por Autor "Porto, Arilza de Oliveira"
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Item Analytical application of positron lifetime spectroscopy in the characterization of binary solid solutions.(1995) Porto, Arilza de Oliveira; Magalhães, Welington Ferreira de; Carvalho, Cornélio de Freitas; Machado, José CaetanoPositron Lifetime Spectroscopy (LS) measurements were performed in a series of binary molecular solid solutions of the general formula M1−xGxL3, where L(ligand)=acetylacetone, dipivaloylmethane, or N-benzoyl-N-phenylhydroxylamine, M=Al(III), Ga(III) or In(III), as matrix, and G=Cr(III), Mn(III), Fe(III), Co(III), Ru(III), Rh(III) and Ir(III), as guest molecules, and the corresponding mechanical mixtures. For the solid solutions, the o-Ps yield values (I3) decrease very rapidly with the increase of the guest mole fraction, showing a high efficient Ps inhibition process, while for the corresponding mechanical mixtures, these values decrease linearly with the increase of the “guest” molecule concentration, indicating the presence of two distinct phases. These results confirm our previous proposal that the LS technique is able to characterize solid solutions formed by one matrix, in whichI3 values are high, and one guest, in which theI3 values are very low.Item Positron annihilation studies in binary solid solutions of metal betadiketonates, using lifetime and doppler broadening spectroscopies.(1993) Machado, José Caetano; Porto, Arilza de Oliveira; Carvalho, Cornélio de Freitas; Magalhães, Welington Ferreira de; Netto, Antônio MarquesPositron annihilation lifetime (LS) and Doppler broadening annihilation kadiation lineshape (DBARL) spectroscopies measurements were performed in several binary solid solutions of the general formula M(l-x,Gfx,L,3 where M = Al(II1) , Ga(II1) , or In(II1) , as matrix; G = Cr (111) , Mn (111) , Fe (111) , co (111) , Ru (111) , Rh(III), and Ir(III), as guest molecules, L = acetylacetone (acac) or dipivaloylmethane (dpm), and X = guest molecule mole fraction. The studied systems can be classified in two groups: the first one presenting only inhibition of positronium formation and the second one presenting inhibition and quenching effects. The inhibition and quenching constants were determined.