Osamu Aita

Soft X-Ray Absorption Spectra of Some Metal Chlorides

The Cl - L 23 absorption spectra of thin films of CuCl, ZnCl 2 , CdCl 2 , PbCl 2 , MnCl 2 , FeCl 2 , CoCl 2 , NiCl 2 , MgCl 2 , CaCl 2 , SrCl 2 , and BaCl 2 have been measured by the photographic method using synchrotron radiation from a 1.3 Bev electron synchrotron as a soft X-ray source. In all materials studied, other than CaCl 2 , SrCl 2 , and BaCl 2 , the absorption spectra near the threshold show absorption bands probably due to the creation of excitons with holes in the 2 p level of chlorine. The intense and broad absorption continuum beginning around 211 eV is observed in all materials studied. This absorption is assigned to the atomic excitation of Cl - ions. Discussion is given about the profile of each spectrum.

Soft X-Ray Emission Spectra of Light Elements. : I. Li, Be, B, Al and Si

A grazing incidence spectrometer with a concave grating of 2 m radius operating in the wavelength region from 20 A to 1,000 A has been constructed in order to study the electronic structure of solids. With this spectrometer, the lithium K , beryllium K , boron K , aluminum L 2,3 and silicon L 2,3 emission spectra have been measured under the condition of ultra-high vacuum and low target input. The results are considered to give the intrinsic spectral profile nearly free from influence of oxidation and contamination of the specimen. They are compared with the theoretical density-of state curves. Some of the discontinuities in the beryllium K and aluminum L 2,3 emission spectra are attributed to the Van Hove singularities in the valence band.

Photoemission study of benzene adsorbed on Si surfaces

Abstract Chemisorbed states of C 6 H 6 onSi(111)7 × 7 andSi(100)2 × 1 surfaces are studied by Si2 p core-level photoemission and polarization dependent C K photoabsorption measurements. The Si2 p spectrum of theSi(111)7 × 7 surface shows that charge transfer from the rest atom possibly to the adatom occurs upon C 6 H 6 chemisorption. It is considered that the charge transfer plays an important role in chemisorption of C 6 H 6 on theSi(111)7 × 7 surface. The C K photoabsorption spectra of chemisorbed C 6 H 6 show that the C ring plane is nearly parallel to both surfaces. However, C 6 H 6 on theSi(100)2 × 1 surface is distorted by chemisorption.

Cl-L2,3 Absorption Spectra of Alkali Chlorides, Silver Chloride and Thallous Chloride

The Cl - L 2,3 absorption spectra of alkali chlorides, AgCl and TlCl have been measured using an ordinary X-ray tube with tungsten target as a radiation source. Measurements were performed carefully at 300°K, 90°K and 25°K over the photon energy range from 198 to 220 eV. The counting method for detection was more improved than in the previous report and a toroidal pre-reflector was used. Results are compared with the existing results of energy band calculation. It is concluded that sharp absorption bands near the threshold are caused by core-excitons with holes in the 2 p level of chlorine.

Photoemission Study of CeO2 and SrCeO3

Photoemission spectra of CeO2 and SrCeO3 have been measured in the Ce 4d → 4f photoabsorption region. The yield spectra of these compounds resemble each other in shape. The valence-band emission of SrCeO3 shows the resonant enhancement in the giant absorption region and the 4f-derived emission exhibits a single-peak distribution such as obtained in CeO2. Moreover, the Ce 3d photoemission spectrum of SrCeO3 has a three-peak structure. These results indicate the strength of the hybridization between the Ce 4f and O 2p states in the ground state of SrCeO3 is similar to that in CeO2.

Resonant x-ray emission spectra of CuO and La2CuO4

The 3d → 2p x-ray emission spectra of CuO and La2CuO4 are measured under the selective excitation from the Cu 2p core-level to the Cu 3d level. The main peak is observed at about 1.5 eV below the absorption peak in both materials. The width of the main peak in CuO is somewhat narrower than that in La2CuO4. In La2CuO4, a satellite is observed at 3.5 eV below the main peak, while the spectrum of CuO does not show a satellite clearly. The main peaks in both materials are ascribed to the transition to the 3d9 excited state and the satellite is attributed to the 3d10v-charge-transfer excited state. From the above results, it is confirmed that the hybridization between the 3d9 and 3d10v states is larger in La2CuO4 than in CuO.

3p - 3d resonant photoemission study of at low temperature

We have studied the Co 3d state of in the temperature range 20 - 110 K by using resonant photoemission spectroscopy in the Co photoabsorption region. By raising the sample temperature from 20 to 110 K, the Co 3d derived emission near the top of the valence band is transferred to higher binding-energies, and the relative peak intensity of two peaks in the satellite is changed. This is interpreted by a spin-state transition of the Co ion.

5p→3d X-Ray Emission Spectra under the X-Ray Excitation in LaF3, La2O3 and CeF3

X-ray emission spectra (XES) due to the 5 p →3 d electronic transition in LaF 3 , La 2 O 3 and CeF 3 are investigated by the X-ray excitation and the electron bombardment. Strong variation in the shape of XES in these compounds is observed in the X-ray excitation. It is shown by a theoretical analysis that this variation is mainly due to the difference of the hybridization effect in the excited state with a 3 d core hole. In the electron bombardment, the spectral features are not so much changed among these compounds as in the X-ray excitation, because the 3d 4 f n +1 configuration created by the 3 d →4 f direct excitation hardly hybridizes with the 3d 4 f n +2 L configuration.

Rare-Earth N4,5 Absorption Spectra of Some Rare-Earth Compounds

The rare-earth N 4,5 absorption spectra of rare-earth compounds RCl 3 , (R=La, Ce, Sm, Eu and Gd) and RB 6 (R=La and Sm) were measured to obtain the informationon the excited state 4 d 9 4 f n +1 of these substances, where n equals the number of the 4 f electrons in the ground state. The structures of the absorption spectra are well explained by the multiplet states of the 4 d 9 4 f n +1 configuration in the final state. The Sm N 4,5 absorption spectrum of SmB 6 shows no distinct indication due to the Sm 2+ ion regardless of the valence mixing between the Sm 2+ and Sm 3+ ions. The absorption structure corresponding to the Sm 2+ ion may be smeared owing to the autoionization process of the excited state 4 d 9 4 f 7 of the Sm 2+ ion because this state is located above the 4 d ionization threshold of the Sm 2+ ion.

Sm M4,5 Spectra of Metallic Samarium and Samarium Hexaboride

The samarium M 4,5 emission and absorption spectra of Sm-metal and SmB 6 were studied. It was found that the spectra of these materials are in close resemblance. The emission spectra obtained by higher excitation energies exhibit appreciable effects of self-absorption because of the presence of absorption peaks in the same energy region. Contrary to the case of the L -edge absorption the M 4,5 absorption of SmB 6 showed no distinct indication of the difference due to Sm 3+ and Sm 2+ ions. The spectra of Sm 2 O 3 , SmS and SmSe were also studied, and it was observed that they have common features among themselves regardless of the difference in the valence of Sm ions.