Dear Feff users, lately, we measured a sample containing Sb and Te at EXAFS beamline CEMO, Hasylab and are wondering whether one can determine the stoichiometry from the height of the different K edges´ steps, if one normalizes the values on the edge steps of the elements (cf. http://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html). The absorption gases and the specimen were not changed for the different K edges. Of course, I have already tried doing so and from statistical reproducibility and from the resulting values compared to the expected ones I would estimate an error of this method of about 1%. A source of error that I could imagine originates from the different beam position at different energies combined with a slight inhomogenity in the pressed sample powder. Now my question is: Are there any other sources of error that I should take into accout? Is there any reference on this method from a more experienced user that I could cite? Kind regards, Peter --- Dipl.-Phys. Peter Zalden I. Physikalisches Institut IA, RWTH Aachen, 52056 Aachen EMAIL: zalden@physik.rwth-aachen.de