Takeshi Soga

Uranium-oxygen lattice vibrations of triuranium octoxide

Abstract A tentative assignment of the i.r. spectrum for triuranium octoxide has been made by assuming two structure models of infinite hexagonal UO 3 and UO 2 . It has been found that all the i.r. absorption bands previously observed in the region from 4000 to 90 cm −1 are well explained by the assumption of such models. In order to obtain the approximate force constants of the uranium-oxygen bonds in triuranium octoxide, the normal coordinate analysis of the optically active U-O lattice vibrations has been made on the basis of the two models. The force constants of U-O bonds have been obtained and discussed in some detail.

The resonance Raman effect of uranyl formate in dimethyl sulfoxide.

The resonance Raman scattering spectra of uranyl formate (UO(2)(HCOO)(2)) in dimethyl sulfoxide ((CH(3))(2)SO, DMSO) have been measured under laser excitation of the uranyl ion in resonance with the 1Sigma(g)(+)-->(1)Phi(g) Laport forbidden f-f electronic transitions (ranging from 510 to 450 nm) by using ten output lines with wavelength ranging from 528.7 to 454.5 nm of the argon-ion laser at room temperature. The observed resonance excitation profile resembles the vibronic structure of the electronic absorption spectrum (ABS) but does not completely superimpose on it. Such a discrepancy is quantitatively explained by the interference effect, which occurs noticeably in the UO(2)L(2) (L=NO(3), CH(3)COO, Cl or HCOO)-DMSO system. Transform theory that makes use of the electronic ABS of the resonant electronic state has been applied to predict the Raman excitation profile (REP) of the uranyl totally symmetric stretching vibrational mode. Comparing the experimental REP with the transform theory prediction, it is found that the resonance Raman intensities of this stretching mode depend mainly on the vibronic interaction (non-Condon effect) in excited electronic states. Reliable value of the nuclear displacement on going the 1Sigma(g)(+)-->(1)Phi(g) electronic transition and the amount of charge transferred from the ligand to uranium of uranyl ion both in the ground and excited states are obtained. Elongation of the U-O equilibrium bond length due to the electronic transition is related to the magnitude of the change in the excitation profile, and has linear relation to the change in the amount of charge transferred from the ligand to uranium of uranyl ion in UO(2)L(2) type uranyl compounds in DMSO.

New in-situ parallel-detection electron energy-loss spectroscopy of SiC crystals irradiated with hydrogen ions

Abstract Structural and compositional changes in SiC crystal due to hydrogen irradiation are examined by electron microscopy and electron energy-loss spectroscopy. Amorphization was observed for a fluence above a value of 3 × 10 21 ions / m 2 . The plasmon loss peaks at 22.7 eV were found to shift to the lower energy side for the hydrogen-ion fluence of above 1.5 × 10 21 / m 2 by use of parallel-EELS. From the shift of the plasmon loss peak, the ratio of composition. Si/C was estimated to be about 1.2 after hydrogen-ion irradiation to a fluence of 6.5 × 10 21 ions / m 2 . Furthermore, a shoulder appearing in the lower energy side of this plasmon loss peak was observed. From the differential curves of these spectra, it is considered that hydrogen atoms implanted into SiC crystals exist in the forms of both hydrogen molecules and C-H compounds.

Oxygen K-Edge Fine Structure of Tl1Ba2Can-1CunO2n+3 Studied by Electron Energy Loss Spectroscopy

The fine structures of the oxygen K-edge in the Tl1Ba2Can-1CunO2n+3 with single Tl-O layers were investigated by electron energy loss spectroscopy (EELS). The peak corresponding to the hole state near the Fermi energy was sensitive to the number of Cu-O layers and the direction of momentum excitation. It was shown that the hole content in Tl1Ba2Can-1CunO2n+3 decreases with the increase of n (n=2–4) and that most holes exist in the O 2px,y orbitals of 2-dimensional Cu-O planes.

The resonance Raman effect of dicaesium uranyl tetrachloride in dimethyl sulfoxide.

The resonance Raman scattering spectra of dicaesium uranyl tetrachloride (Cs2UO2Cl4) in dimethyl sulfoxide ((CH3)2SO) have been measured under laser excitation of the uranyl ion in resonance with the 1sigma(g)+ --> 1phi(g) Laport-forbidden f-f electronic transitions (520-450 nm) by using 10 output lines of the argon-ion laser at room temperature. The excitation profile of the totally symmetric stretching vibrational mode of uranyl observed at 830 cm(-1) is presented and analyzed in terms of the transform methods which are able to formally bypass multimode complexities. The non-Condon model (generalized B, C-terms of scattering) gives a relatively good agreement with the resonance excitation profile of experiment. Reliable value of the nuclear displacement on going the 1sigma(g)+ --> 1phi(g) electronic transition and the amount of charge transferred from the ligand to uranium of uranyl ion both in the ground and excited states are obtained. It is found that the average number of ligands coordinated equatorically to the central uranium atom affects on the amount of charge transferred from the ligand to uranium, especially in the electronic excited state. As increasing the average number of ligands, the amount of charge transferred from the ligand to uranium increases in the ground state, while in the electronic excited state, the charge transferred decreases.

Resonance Raman excitation profile for uranyl acetate in dimethyl sulfoxide

Abstract The intensity of Raman lines of uranyl acetate/UO2(CH3COO)2 in dimethyl sulfoxide has been measured as a function of excitation energy in the region of the Laport-forbidden f–f electronic transitions, using ten output lines of an argon-ion laser. The resonance Raman excitation profile of the totally symmetric stretching vibration of the uranyl observed at 829 cm−1 shows vibrational fine structure, which resembles the vibronic structure of the electronic absorption spectrum but does not completely coincide. Experimental excitation profile is compared to that calculated using transform theory with parameters derived from the observed absorption spectrum of the resonant electronic state of interest. The non-Condon model (generalized B, C-term source of scattering) gives relatively good agreement with experimental results. The disagreement between the experimental data and the calculated resonance Raman excitation profile may be ascribed to interference between the weak scattering from the neighboring forbidden electronic states and strong preresonance scattering from allowed electronic states at higher level. The change in the UO equilibrium bond length resulting from the 1Σ+g→1Φg electronic transition is found to be 0.068 A.

Electron energy loss spectroscopy on oxygen k-edge fine structure of YBa2Cu3Oycontaining dopants (La, Ca, Co)

The fine structures of the oxygen K-edge in the Y-Ba-Cu-O system, in which hole content was controlled by reducing the oxygen content and doping elements (La, Ca and Co), were investigated by electron energy loss spectroscopy (EELS). When Ba(+2) and Y(+3) were replaced by La(+3) and Ca(+2), respectively, the oxygen content of the sample changed and the peak corresponding to the hole state near the Fermi energy sensitively changed with the average hole content. When Cu(+2) was replaced by Co(+3), Tc decreased drastically and the peak at the oxygen K-edge shifted to higher energy.

The resonance Raman effect of UO2L2 (L = NO3, CH3COO or Cl) type uranyl compounds in dimethyl sulfoxide

The resonance Raman scattering spectra of UO2L2 (L = NO3, CH3COO or Cl) type uranyl compounds in dimethyl sulfoxide ((CH3)2SO) have been measured under laser excitation of the UO22+ ion in resonance with the 1Σg+ -->1Φg Laport-forbidden f-f electronic transition. The resonance Raman excitation profiles of the totally symmetric stretching vibrational mode of uranyl are presented and analyzed in terms of transform theory within the non-Condon model It is found that, in the 1Σ+g -->1Φg electronic transition, elongation of the U-O equilibrium bond length is related to the magnitude of the change in the excitation profile and has a linear correlation with the increase in the charge transferred from the ligand to the uranium atom.