Toshiteru Maeda

In situ SERS study of water molecules on silver electrodes in alkali-hydroxide solutions

In situ surface enhanced Raman has been used to study water molecules adsorbed on a silver electrode in 0.5 M alkali-hydroxide aqueous solutions. Raman spectra and cyclic voltammograms were measured simultaneously while the electrode potential was swept continuously. The alkali-hydroxide solutions were LiOH, NaOH, KOH and CsOH. Raman lines associated with water molecules are identified by a comparison with those obtained for aqueous solutions with D2O instead of H2O. Strong Raman lines, which are associated with the existence of oxygen species adsorbed on silver electrode, were observed in a limited region of electrode potential. The variation of Raman intensities of water molecules, when the electrode potential is scanned, is discussed in terms of the different roles of the cations of the respective alkali-hydroxide solutions.

Phonon modes in single-wall nanotubes with a small diameter

Abstract Phonon modes in single-walled nanotubes (SWNTs) of carbon are reexamined within the framework of a force constant model. In order to explore the effect of curvature of tubules with a small diameter, the dynamical matrices are formulated in terms of cylindrical coordinates. The curvature effect of tubules is discussed by comparing with the results obtained by the zone folding model. The diameter dependent properties of phonon modes are shown to be useful for analyzing the size distribution of SWNT in the synthesized samples.

Melting and Discharge Phenomena of Breaking Ag Contacts Using a Precisely Controlled Piezoelectric Actuator

Using a laminated ceramic piezoelectric actuator for a very slow (4 m/s) precisely controlled make/break operation, contact voltage Vc and contact current Ic, residue of melt surface and discharge for breaking hinge relays with Ag contacting electrodes are measured. To control mechanical conditions, the movable electrode had a finely shaped convex surface (curvature radius: 0.5 mm) and a flat fixed electrode. Make/break operation was attempted only once due to transformation of contact surface. Then, Vc and Ic were measured at 1.5 to 25 V and 0.1 to 5 A. Fusion spots and residue of electric discharge on the contact surface were quantitatively measured using a laser microscope. Even when Vc and Ic were larger than the minimum arc voltage and minimum arc current, respectively, a continuous arc discharge occasionally did not occur. For the case of Vc=25 V and Ic=1 A, electric discharge was spontaneously suppressed to less than 100 s. The displacement of the movable electrode was estimated to be several nanometers for the discharging time interval. The residues of discharge were multiple damaged spots in the range of 100 m in radius, which had a black and/or white rectangular convex and concave shape.

Brillouin Light Scattering from Thin Albumen of Chicken Egg

Chicken eggs are rich in high-quality proteins and several kinds of trace elements, and have been a very familiar nutriment for human beings since ancient times. Chicken egg white comprises two layers, namely, thin albumen and thick albumen, both surrounding the yolk within a shell. There are two types of thin albumen known as the outer and inner thin albumens. The physical properties of both types of albumen are essentially the same. Thin albumen from chicken egg, hereafter referred to as egg white (EW), gels at a gelation temperature TG of ca. 66 C. The gelation process and the rheological properties of EW have attracted the attention of biological and biochemical scientists, food scientists, and physicists. The gelation process of EW has been studied by the ultrasound pulse technique at 3MHz in the temperature range between 10 and 95 C. The velocity of a longitudinal sound wave (LSW) exhibits a broader peak with a maximum at approximately 66 C as temperature increases through the sol–gel transition. Brillouin light scattering (BLS) measurement is another powerful and convenient technique for studying thermally excited hypersonic sound waves in the GHz frequency region. By utilizing a (3+3)-pass Fabry– Perot interferometer (FPI), we expect to observe a BLS spectrum from EW even near TG. We purchased fresh Boris Brown eggs with a red shell laid within a day at a farmers market near our university just before each measurement. About 5ml of thin albumen or distilled water was transferred into a glass tube placed in a brass cell. The cell temperature was regulated up to 82 C within an accuracy of 0:1 C and monitored by an almel– chromel thermocouple. We repeated our BLS measurement six times only during a heating run. BLS spectra were probed using the 1⁄4 488 nm excitation from an Arþ laser in a single-cavity mode with an output power of 40mW. BLS spectra were obtained using a laboratory-built (3+3)-pass FPI. Since EW gradually becomes opalescent with increasing temperature above 50 C, we employed the 180 scattering geometry, which allows us to continue our BLS measurements up to 61 C. In order to determine the LSW velocity V and the refractive index n at 488 nm, we also adopted the 90A scattering geometry at 24 C. Figure 1 shows an example of the 180 and 90A BLS spectra of EW at 24 C. We performed a numerical convolution analysis of these BLS spectra by adopting the damped harmonic oscillator (DHO) function for the elastic response function Sðq; !Þ;

Brillouin Light Scattering Study of Hypersonic Velocity Dispersion in Aqueous Sucrose Solutions

Sucrose (C12H22O11) is a nonreducing disaccharide comprising of one glucose ring (C6H12O6) and one fructose ring (C6H12O6) bridged through a C–O–C linkage. The physical properties of aqueous sucrose solutions have been intensively investigated over a long period of time. The temperature vs concentration (d in wt%) phase diagram of the sucrose-water system reveals a stable unsaturated liquid region with concentration below 60%, a metastable supercooled region between 60 and 95%, and a glass region above 95% at room temperature. Temperature studies of viscosity indicate that the sucrose-water system can be classified into a fragile glass former. Sugars as glass-forming materials have attracted some attention during the last two decades. The technological and biological importance of the glass transition in sugars, as a food, is now widely recognized, and intensive research activities are being directed towards understanding the glass transition in various sugar-water systems utilizing various experimental techniques. The acoustic properties of glass-forming liquids have been one of the important subjects of Brillouin light scattering (BLS) since the late 1960s. BLS studies on glucose solutions and trehalose solutions have been performed to determine the glass transition temperature TG. However, the acoustic dispersion of sugar solutions has not yet been fully investigated. We examined the acoustic dispersion of sucrose solutions by means of BLS as a function of d up to 79% at 23 C. Unsaturated solutions below d 60% can be prepared at 23 C by dissolving granulated sugar into pure water. For metastable 70 and 79% solutions, granulated sugar was solved into water at 50 and 80 C, and then cooled to 23 C. The sucrose concentration was determined using a conventional refractometer. BLS spectra were probed using the 488 nm line (1⁄4 0) from an Arþ laser in a single cavity mode with an output power of 15mW. Backscattered BLS spectra were obtained using a (3þ 3)-pass tandem Fabry– Perot interferometer. The depolarized BLS component is more than two orders of magnitude weaker than the polarized component. Figure 1 shows the development of the BLS spectrum normalized by spectrum accumulation time as a function of d of up to 70%. Strong modification of the BLS spectrum through viscoelastic coupling between the sound wave and a relaxation mode can be clearly seen above d 1⁄4 40%. The observed BLS spectrum Oðq; !Þ can be written as

Estimation of Frequency Conversion Efficiency of Lasers with Intracavity Optical Mixing

For lasers with intracavity frequency conversion, we present general expressions of the power output efficiencies as a function of the relative length of nonlinear optical crystals for different values of parameters related to fundamental lasers, the nonlinear crystal and optical geometries. The maximum available efficiencies due to the nonlinear interaction are calculated for cases where the optimum coupling conditions are either satisfied or not satisfied. It is explained that the forbidden ranges of nonlinear coupling coefficients are the result of several factors. These results provide useful suggestions for practical construction.