The valence and coordination structure of implanted Cu and Br ions were investigated by x-ray absorption fine structure spectroscopy in (2.4 MeV 6 × 1016 Br2+ ions cm−2+ 2 MeV 6 × 1016 Cu+ ions cm−2)-implanted silica glass. It was found that the implanted Cu and Br atoms were coordinated by oxygen atoms and silicon atoms, respectively, in as-implanted glass. After heating at 600 °C, at least two-thirds of the Cu atoms were coordinated by Br atoms without the formation of crystals. The γCuBr crystal was formed after heating to 1100 °C. It was deduced that the coordination structure of Cu and Br atoms depends on defects as well as thermochemical stability and mass transport processes.

Structure of Cu ions in (Cl+Cu)-, (Br+Cu)-, (I+Cu)-, (S+Cu)- and (Se+Cu)-ion implanted silica glasses has been studied by x-ray absorption and optical absorption spectroscopies. Cu ions formed Cu-O bonds in the as-implanted glasses, due to the homogeneous distribution of Cu ions and the low local concentration of halogen and chalcogen ions in silica glass. Heat treatment at about 600°C caused the formation of bonds between Cu ions and halogen/chalcogen ions without forming Cu halide or chalcogenide crystals. It was deduced that the formation of these bonds was controlled by the diffusion of Cu ions in silica glass. On the other hands, it was inferred that the formation of Cu halide and chalcogenide crystals was controlled not only by the diffusion of halogen/chalcogen ions but also by the diffusion of matrix ions.

Coordination structures of implanted Fe, Co, and Ni ions were studied in 1.78–2.00-MeV 5 × 1016 ions/cm2-implanted silica glasses by x-ray absorption and optical absorption spectroscopies. It was found from x-ray absorption spectra that the implanted Fe, Co, and Ni ions are coordinated by ca.3 oxygen atoms. The implanted ions dispersed in glass matrix and did not form crystals. The valence of the implanted ions was about 1.5. The Fe–O, Co–O, and Ni–O interatomic distances were 190, 191, and 192 pm, respectively. In addition, it was found from optical absorption spectra that one-fifth of implanted Co ions were present as Co2+ ions in tetrahedral symmetry.

180 keV Mn+ ions were implanted in silica glass at doses ranging from 1×1016 to 2×1017 ions/cm2 at room temperature. The coordination structure of implanted Mn atoms was studied by X-ray absorption spectroscopy. It was found that Mn atoms were mainly coordinated by O atoms in silica glasses as-implanted at doses lower than 5×1016Mn+ions/cm2. The Mn-O bond distance was 2.07 Å and the coordination number was 4.3 in average. Mn atoms were mainly coordinated by Mn and O atoms in the glasses as-implanted at doses higher than 1×1017 Mn+ions/cm2. In all the glasses, Mn atoms which are coordinated by O atoms were present as divalent state. After heating at 700 °C in air, Mn atoms were present as trivalent state and tended to form oxide crystals.

Coordination state of gold atoms implanted in silica glass to an energy of 1.5 MeV and a dose of 1 × 1017 ions/cm2 has been studied by x-ray absorption fine structure spectroscopy. It was found that most of the gold atoms form gold clusters in which the nearest neighboring Au–Au interatomic distance is shorter by 0.05 °A than that in bulk gold. The contraction of Au–Au interatomic distance of gold clusters in silica glass is less than that reported in the previous studies on gold clusters within the other substrates. Gold atoms are coordinated by about four gold atoms in average. In addition, it was found that Au–O bonds are formed at the gold clusters/silica glass interface. It was deduced that the formation of Au–O bond at the gold clusters/silica glass interface depresses the contraction of Au–Au interatomic distance.

The local structure and crystallization behavior of Nd15Fe77Bx (x = 2−14) melt-spun alloys were studied by Nd L3 extended x-ray absorption fine structure (EXAFS). The conventional x-ray powder diffractometry studies showed that the Nd–Fe–B melt-spun ribbons had the amorphous structure regardless of the boron content. EXAFS studies of the local structure around the Nd atom confirmed that the Nd–Fe–B melt-spun alloys had the amorphous structure and virtually the same nearest neighbor distance from the Nd atom. The amorphous alloys were heated by a differential scanning calorimetry in order to investigate the variation in the local structure during the crystallization process by EXAFS measurements. Although no appreciable difference was found in the nearest neighbor distance of the Nd atom between the amorphous alloys and the crystallized alloys, the small variation in the nearest neighbor distance during the crystallization process was detected by EXAFS measurements.

The structure of ultrafine gold particles embedded in silica glass by ion implantation has been studied by x-ray absorption fine structure spectroscopy. It is found that the Au–Au interatomic distance in the particles is very similar to that in bulk gold within 0.01 Å. Mean-square relative displacement in the particles is 1.2–1.3 times larger than that in bulk gold.

Thermal relaxation of glass structure has been studied on silica glasses densified by hot isostatic pressing. Density of the glasses relaxed toward the value of an undensified glass by thermal annealing. Relaxation rates of density of the glasses were measured after the annealing at several temperatures. Fast and slow relaxation processes were found from the analysis by using a stretched exponential relaxation function Φ(t)=exp{−(t/τeffβ}). The slow process becomes dominant after the fast process. Raman scattering spectrum also has been measured through the thermal relaxation. The width of the main band at 450cm−1 increased by the annealing and recovered the value for the undensified glass after the fast process. The bands at 1060 and 1200 cm−1 shifted back to the positions for the undensified glass. The high density state(Δρ/ρ∼0.5%), however, was maintained even after the fast process. From these results, it is deduced that the fast process is due to the recovery of the O3Si-O-SiO3 tilt angle and Si-O-Si bond angle to the mean values for the undensified glass.

Degenerate four-wave mixing experiments have been performed for Au colloid-doped glasses prepared by melting and sputtering methods. The nonlinear optical properties of the glasses are discussed from viewpoint of the concentration of the Au colloid particles and the thickness of the glasses. We also discuss the dependence of the nonlinear properties on the pulse duration of laser for the measurements, and a very slow relaxation.