Curious "doublet" resonances in the KL double photoexcitation spectrum of argon are explained as a strong admixture of 3d' excited states to the principal [1s2p]4p excitation. A simulated "ab initio" EL photoabsorption spectrum including shake-up and shake-off contributions agrees well with the experimental data.
The x-ray absorption of transition metals from Cr to Zn is examined in the energy region of E+L double photoabsorption. A variational procedure is developed to extract correlated components from pairs of spectra. Applied to absorption spectra taken at different sample temperatures, the procedure is used to suppress the extended x-ray-absorption fine-structure oscillations that pervade the E +L region in this range of elements. A relative sensitivity of 2X10 ' to 3X10 of the absorption coefficient, depending on the sample quality, is achieved. No significant features attributable to multiple photoexcitation are found in the spectra on that level, so that previous reports of E +L edges for Co, Ni, and Zn are not confirmed.
The International Atomic Energy Agency maintains a database on internationally available certified reference materials of natural origin. The database was updated in 1998 and prepared for an Internet implementation. A user-friendly structure was created, providing two main pathways for browsing, either according to the matrix classification or the producer's name. The database presently contains over 20,000 values for 480 measurands and 1085 reference materials from 43 different producers. Most of the materials entered contain values for trace and minor elements (66%).
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