The magnetic properties of LnIII and AnIII complexes formed with dipicolinate ligands have been studied by NMR spectroscopy. To know precisely the geometries of these complexes, a crystallographic study by single‐crystal X‐ray diffraction (XRD) and extended X‐ray absorption fine structure (EXAFS) in solution was performed. Several methods to separate the paramagnetic shifts observed in the NMR spectra were applied to these complexes. Methods using a number of nuclei of the dipicolinate ligands revealed an abrupt change in the geometries of the complexes and a metal–ligand interaction in the middle of the lanthanide series. A study of the variation of the paramagnetic shifts with temperature demonstrated that higher‐order terms of the dipolar and contact contributions are required, especially for the lightest LnIII and almost all the studied AnIII. Bleaney's parameters a and CaD relating to the contact and dipolar terms, respectively, were deduced from experimental data and compared with the results of ab initio calculations. Quite a good agreement was found for the temperature dependencies of a and CaD . However, the CaD values obtained from cation magnetic anisotropy calculations showed some discrepancies with the values derived from Bleaney's equation defined for LnIII. Other parameters, such as the crystal field parameter and the hyperfine constants Fi obtained from the experimental data of the [An(ethyl‐dpa)3]3− complexes (ethyl‐dpa=4‐ethyl‐2,6‐dipicolinic acid), are at odds with the assumptions underlying Bleaney's theory.

The MARS beamline at the SOLEIL synchrotron is dedicated to the characterization of radioactive material samples. One great advantage of the beamline is the possibility to characterize about 380 radionuclides by different X-ray techniques in the same place. This facility is unique in Europe. A wide energy range from around 3.5 keV to 36 keV K-edges from K to Cs, and L3 edges from Cd to Am and beyond can be used. The MARS beamline is optimized for X-ray absorption spectroscopy techniques (XANES/EXAFS), powder diffraction (XRD) but x-ray fluorescence (XRF) analysis, High Energy Resolution Fluorescence Detected -XAS (HERFD-XAS), X-ray Emission (XES) and -XAS/XRD are also possible. A description of the beamline as well as its performances are given in a first part. Then some scientific examples of XAS studies from users are presented which cover a wide variety of topics in radiochemistry and nuclear materials.

The complexation of 1,4,7,10-tetrazacyclodecane-1,4,7,10-tetraacetic acid (DOTA) ligand with two trivalent actinides (Am and Pu) was investigated by UV-visible spectrophotometry, NMR spectroscopy, and extended X-ray absorption fine structure in conjunction with computational methods. The complexation process of these two cations is similar to what has been previously observed with lanthanides(III) of similar ionic radius. The complexation takes place in different steps and ends with the formation of a (1:1) complex [(An(III)DOTA)(HO)], where the cation is bonded to the nitrogen atoms of the ring, the four carboxylate arms, and a water molecule to complete the coordination sphere. The formation of An(III)-DOTA complexes is faster than the Ln(III)-DOTA systems of equivalent ionic radius. Furthermore, it is found that An-N distances are slightly shorter than Ln-N distances. Theoretical calculations showed that the slightly higher affinity of DOTA toward Am over Nd is correlated with slightly enhanced ligand-to-metal charge donation arising from oxygen and nitrogen atoms.

This paper reports the characterization of ternary II-VI semiconductor nanocrystals, deposited by the electrochemical atomic layer epitaxy (ECALE) technique.In particular, morphological and structural properties of the ternary compounds of formula Cd x Zn 1−x Se deposited on Ag (1 1 1) have been characterized as a function of composition. The number of the attainable x values is limited by the necessity of using well-defined ZnSe/CdSe deposition sequences. However, the quantitative analysis carried out on the basis of both electrochemical and extended X-ray absorption fine structure (EXAFS) experiments indicates that the ECALE method is a successful way of controlling the composition of Cd x Zn 1−x Se. In addition, the electrochemical measurements show that the amount of deposition is minimum in correspondence to the compound with x = 0.5, thus corroborating the hypothesis of a higher degree of disorder suggested both by morphological and structural investigation. The morphology was studied by atomic force microscopy (AFM). The structure of the films is estimated by EXAFS which is a powerful technique for the analysis of the local structure around chosen atoms.

Abstract