Spectrum Decomposition through Maximum Likelihood Common Factor Analysis of the EPR Spectra of Na+ Containing Carbonated Apatites Dried at 400°C

Abstract

X-irradiated carbonated apatites precipitated from aqueous solutions and dried at 400 degrees C until constant weight are investigated with electron paramagnetic resonance (EPR). The carbonate content of the samples studied ranges from 8.12 to 21.0 wt%. The observed multicomponent EPR spectra are analyzed with maximum likelihood common factor analysis (MLCFA), a multivariate statistical technique. Once the correct number of constituents are determined and the factor spectra estimated by MLCFA, a minimization procedure is performed in order to transform the abstract factor spectra linearly into an equal number of real EPR powder spectra. The spin hamiltonian parameters of the component spectra thus obtained are used to characterize and identify the different paramagnetic radicals. A comparison with values from the literature is made. A spectrum decomposition study of all the observed multicomponent EPR spectra in terms of the isolated constituents is successfully performed as a function of the carbonate content of the samples.