Using magnetically enhanced terahertz radiation from InAs, various naphthols, which exhibits estrogenic like activity and are potentially mimic natural hormones, are studied. The experimental results show that the naphthols, depicted by the position of the hydroxyl (-OH) component at different carbon atom sites of the naphthalene compound, are distinguishable based on the absorption of THz radiation. It is found that the THz radiation absorption is strongly related to the crystal symmetry and dipole moment of these isomers.

At various Ce(IV)/DPP (DPP: diphenyl phosphate) molar ratios, the structure of Ce clusters in aqueous solutions was studied by extended x-ray absorption fine structure measurements. Although the Ce–Ce bond was strong in the absence of DPP, the corresponding signal was significantly reduced when the Ce(IV)/DPP molar ratio was 1. The result indicates the existence of a strong interaction between Ce(IV) ions and DPP, and suggests the formation of a Ce–DPP structure in solution. With an increase in the molar ratio, the signal of Ce–Ce bonds increased again, and exceeded that observed in the absence of DPP, suggesting the formation of a Ce–Ce–DPP structure. Ce(IV) ions in the complexes were found to have ∼0.67 4f electrons. On the other hand, no measurable charge transfer was observed in the case of Ce(III) ions. These results demonstrate the role of the 4f orbital of Ce(IV) ions for its enormous activity for DNA hydrolysis.

Local structures around Mn in Ga1-xMnxAs (x= 0.005 and 0.074) films have been studied using Mn K-edge extended x-ray-absorption fine structure. In the Ga1-xMnxAs films, Mn atoms are substituted into the Ga sites in the zinc-blende-type GaAs lattice. The Mn-As bond length (2.49-2.50 Angstrom) in Ga1-xMnxAs is 2-3% larger than the Ga-As bond length (2.44 Angstrom) in bulk GaAs. The longer;Mn-As bonds cause local disorder in the GaAs lattice, the degree of which increases with the Mn composition. [S0163-1829(98)00527-X].

We report on reflectance difference spectroscopy (RDS) from highly oriented, single-domain (2X1) reconstructed Si(001) surfaces. It is much closer to the "ideal" surface than the vicinal one commonly used in RDS. It was prepared using electromigration technique which resulted in large terraces (5 mu m). Certain features that are attributed to 2X1 and 2X2 structures are significantly changed in spectra obtained from vicinal surfaces. This indicates that the steps suppress formation of the 2X2 structures. The vicinal surfaces may have limited practical utility in RDS studies of the Si(001) surface.

The kinetics of hydrogen adsorption on Si(001) has been studied by reflectance difference spectroscopy (RDS). We measured the hydrogen coverage on Si(001) estimated from the peak intensity of RDS, which is sensitive to hydrogen termination of the dangling bonds of silicon dimers. A detailed study of the adsorption kinetics showed that atomic hydrogen adsorbed on Si(001) with a `hot precursor' mechanism, in which the adsorbed hydrogen can roam across the surface in search of an unoccupied dangling bond to terminate. In the hydrogen termination, the peaks of RDS changed in different ways. This indicates that the peaks have different origins.

The structure of Ge dimers on well-oriented Si(001) has been studied by surface-sensitive X-ray absorption fine structure (XAFS) technique in situ after the growth by molecular beam epitaxy (MBE). The bond lengths values for adatom-adatom and adatom-substrate pairs were determined from the Ge K-extended X-ray absorption fine structure (EXAFS). For 1 monolayer (ML) Ge on Si(001), the elongated Ge dimer structure with the GeGe bond length of 2.51 ± 0.01 Å was observed. The observed local structure around Ge atoms indicates that the adatoms take the p3-like configuration commonly observed for symmetric dimers. The results suggest that a substrate-to-adatom charge transfer is induced by surface strain.

We have investigated the bond length relaxation in monolayer InP1-xAsx epitaxially grown on the InP(001) substrate by use of extended X-ray absorption fine structure with synchrotron radiation. The In-As bond lengths were determined over a wide range in As composition x (0.08

The role of surface strain in interfacg.mi$ng during molecular beam epitaxy (MBE) growth of 9g q9 Slgn Si(001) has been studied.by-syrfacZ-sensitive X-ray ubsoaition-nn""rt ucture (xAFS)r The effect of Bi surfactant on inierfaie mixing *ur rroJ#o ui itt'riroiai oisttiuution around Ge atoms in Gesi heterointerfaces. It was foun? tfrat ni suifu6tunt"iu"li"*uti;"lit suppressinterface mixing bqsed o.n twq pathways of migration aiong th" g;&itt Oitection, i.e., surface segregation and the interch'ange with subslraie. n6results indicate that the :,ult3?e strain opg.n-s up.layerand site-specific migration channels between the iecond and thtrd laygrs. Possible microscopic mechanism of intErface mixing induced bt itfage strain is proposed.

The surface of an organic high-Tc superconductor, (BEDT-TTF)2[Cu(NCS)2] [BEDT-TTF: bis(ethylenedithio)tetrathiafulvalene, Tc=10.4 K under ambient pressure], was observed with a scanning tunneling microscope in air and at room temperature. The step height observed on its surface was 13.2 Å and was very close to the one layer thickness of the (BEDT-TTF)2[Cu(NCS)2] crystal (15.22 Å, determined by x-ray diffraction). Periodic zig-zag structures were observed along the diagonal line of the surface unit cell and agreed well with the two-dimensional BEDT–TFF molecular structure projected onto its crystal b-c plane.