Estimation of the experimental standard deviations in EXAFS measurements

Abstract

We have studied the multiple recording method to estimate if it possible to obtain by this way reliable EXAFS data standard deviations. The examination of more than 10 different samples, each of them recorded at least 8 times, gave us the possibility to show that the partial standard deviations follow the expected probability laws. Even when the number of samples is small, it is possible to give a reasonable upper limit of ε wich could be used as the statistical contribution of the experimental error bars. In some cases we have found that a uniform weighting by 1/ε2 may fail to give a good fit, especially in the high part of k space. We present a simple method of weighting which lead to more satisfying fits without loosing the correct normalisation of the fitted Δχ2 necessary to obtain correct fitted parameters error bars.