Polarographic studies on the electrode kinetics of the nickel(II) complexes with glycine and some of its derivatives: I. glycine complexes

D.C. polarograms of the Ni(II)-glycine complexes were measured with varying pH values at constant total glycine concentration (0.05 M) and conversely with varying total glycine concentration at constant pH values (3.5, 4.5, 7.5 and 9.5). The current—voltage curves obtained were analysed to determine the limiting currents, the transfer coefficients, and the half-wave potentials, by using the non-linear least squares method. From the dependence of the half-wave potentials on the free glycine concentration, the mechanism of the electrode processes was elucidated. It was shown that the first wave corresponded to the reduction of the Ni²⁺ aquo-complex, the second to the NiG⁺ complex, the third to the NiG₂ complex and the fourth to the NiG^?₃ complex. The kinetic parameters for the four charge transfer processes were determined.The second and third waves were kinetic in character and the rate constants of the dissociation and association reactions between NiG⁺ and NiG₂ and between NiG₂ and NiG^?₃ were determined by analysing the dependence of the kinetic limiting currents on the free glycine concentration.     

Three-dimensional athermal waveguide at 1.3 μm wavelength for temperature independent lightwave devices

To eliminate the temperature dependence of narrow-band filter, a three-dimensional athermal waveguide of which optical path length is independent of temperature was developed at 1.3 μm wavelength. The temperature coefficient of the refractive index of films made of glass materials was measured at this wavelength, and a strip-loaded athermal waveguide was designed using a scalar finite element method. The temperature coefficient of optical path length was successfully decreased to 9.65X10^-9[/K] (0.1% of the conventional waveguide).     

An analysis of medium noise of Co-Cr double-layer films in perpendicular magnetic recording

The medium noise in perpendicular magnetic recording is discussed. The perpendicular recording mode was expected to prevent zig-zag walls around transitions, and the experimental result of low transition noise in Co-Cr media confirms this. Also, the main origin of the noise is concluded to be irregular clusters of grains in the film.     

Persistence of Si(111)7 × 7 surface structure under air exposure

Changes in Si(111) 7 × 7 pattern with air exposure are studied by RHEED. The relation between exposure time and air-oxidized film thickness is obtained using an ellipsometer. As a result, it is found that the 7 × 7 surface after air exposure (760 Torr, 20 h) still exhibits several 7 × 7 spots near normal ones in the RHEED pattern. The air-oxidized film thickness corresponding to this exposure is about 13 Å. The fact that the 7 × 7 spots do not disappear with HF etching of the oxide film indicates that the superstructure remains not at the oxide surface but at the substrate selvedge. The 7 × 7 spots gradually disappear after longer exposure time and no 7 × 7 spots can be observed after 40 h (about 15 Å in oxide thickness). For a sample exposed longer than 40 h, no 7 × 7 spots reappear, even if the oxide is removed by HF. Therefore, it is concluded that the structure of the substrate selvedge changes with exposure time.     

Temperature dependence of the lattice vibrations of triglycine selenate

The polarized Raman spectra below 300 cm^?1 and the far infrared spectra from 400 to 30 cm^?1 of triglycine selenate were measured at various low temperatures. It was found that the Raman doublet at 44 and 38 cm^-1 observed in the paraelectric phase (space group C²_2h) was reduced to a singlet at 38 cm^?1 in the ferroelectric phase (space group C₂²). This spectral anomaly in the paraelectric phase appears to be due to the splitting of the translational mode of glycine I along the crystallographic b axis, the splitting being caused by the tunneling of glycine I across the barrier between the two potential minima which are located symmetrically on either side of the crystallographic ac plane (i.e. at $\text{b =}\text{1}\text{4}$ and $\text{3}\text{4}\text{)}$. New Raman bands which appear below the Curie temperature are also discussed.