Narrow Results

Partial M-x-ray production cross sections, which have not been well investigated up to the present, were measured in detail for six heavy lanthanides; Dy, Ho, Er, Tm, Yb and Lu. As a result, it is found that intensities of Mα,β lines, which are dominant among all the M-x-rays, and (M1-N2, M1-N3, M2-N4) lines agree well with those predicted by theory. However, clear discrepancy is found for Mζ and Mγ x-rays. Although it was pointed out by a PIXE analysis with a high-resolution crystal spectrometer that special attention must be paid for an analysis of Mζ and Mγ lines, it is found from the present work that it is possible to perform quantitative analysis using Mα,β lines.

Partial L- and M-x-ray production cross sections for Dy, Er and Lu have been systematically measured over the wide projectile-energy range of 3-40 MeV/amu for proton and ³He-ion impact, and values of partial x-ray production cross sections were compared with those predicted by the ECPSSR theory. As the result, it is confirmed that the ECPSSR theory gives consistent ionization cross sections for each subshell in L- and M-shells. It is also found that values of x-ray transition rate are correct for Mα,β and Lα₁₂ lines which are predominant in M and L x-ray spectra, respectively. However, it is pointed out that some of the values of x-ray transition rates must be revised, and improved values were obtained experimentally for the first time.

X-ray absorption measurements have been made at the CuL₃ and O K-edge on (Hg_0.5Bi_0.5)Sr₂(Ca_1-xPr_x)Cu₂O_7-δ (x=0.35,0.50) and (Hg_0.5Bi_0.5)Sr₂(Ca_0.65Nd_0.35)-Cu₂O_7-δ superconducting systems. Our results clearly indicate that hole density decreases with increase in Pr content. The values of T_c for Pr and Nd (x=0.35) systems are the same but the itinerant hole density is found to be larger in the latter case. In view of the fact that the density of holes depends more upon diamagnetic fraction than the T_c in these superconducting systems, we can conclude that superconducting properties are different for these two cases.

With the advent of modern synchrotron radiation facilities, fluorescence-detected X-ray absorption spectroscopy (XAS) has proven its capability as a highly sensitive local structural tool. Previous applications have been limited to dilute systems and thin films where the absorption of incoming incidence X-ray and outgoing fluorescence X-ray can be neglected. In this chapter we describe unconventional applications beyond this criterion, which are made possible by improving detection efficiency by orders of magnitude combining a high flux insertion devices and highly efficient detectors. In the first application, the non-equilibrium local structure of photo-induced phase of Fe(II) spin crossover complex, [Fe(2-pic)₃]Cl₂EtOH (2-pic=2-aminomethyl pyridine), was investigated under laser illumination. The results indicated no symmetry breaking of FeN₆ clusters upon spin-state switching, establishing the origin of new Raman lines as unrelaxed “frozen-in” distorted outer ligand molecules. Secondly, we demonstrate that polarization-dependent XAS is obtained with a high quality for high temperature superconducting (HTSC) single crystals. The results of temperature-dependent local lattice study on high-quality single crystal of LaSr- CuO revealed doping-induced local lattice distortion $T_d^{\max }$ that maximizes at the superconducting critical temperature $T_c^{\max }$, indicating the strong intimacy of HTSC with local lattice, casting doubts to the purely electronic pairing mechanisms that ignore the contribution of lattice. Lastly, we describe that, combining a microfluidic cell with a fluorescence detection, position-dependent XAS provides time-dependent XAS for dilute systems. The application to CdSe nanocrystal formation demonstrated that such an approach would allow in situ studies on the structural evolution of intermediate state of nanocluster formation known as puzzling state, i.e. “monomers”, in association with molecular orbital calculations. Because of a limited space, unconventional applications are briefly described in this chapter but it could be sufficient to expect more outputs from the 4^th generation synchrotron facilities that would allow higher brilliance and a smaller focus size because the methodology described here is strongly dependent on synchrotron instrumentation.