Akinori Takami

Size reduction of gold particles in aqueous solution by pulsed laser irradiation

When the gold particles produced by the chemical reduction of hydrogen chloroaurate solution were irradiated by the second harmonic of a pulsed Nd:Yag laser (532 nm), their diameter was reduced from more than several deca-nm to less than 20 nm. At the same time, the shape of the particles, originally nonspherical, became spherical. This phenomenon was limited to pulsed laser, and is caused by the heating of the particles within the very short time of laser irradiation; the very large absorption cross section of the particles at the plasmon absorption and the thermal insulation of the irradiated particles in water should be responsible.

IR spectra of H2S isolated in free-standing crystals of Kr and Xe

Abstract Infrared spectra of H 2 S doped in Kr and Xe free-standing crystals have been measured in their S–H stretching region at 17 K. Banded structures at 2640–2600 cm −1 in Kr and at 2630–2580 cm −1 in Xe have been assigned mainly to the rotational contours of the ν 3 band of isolated H 2 S in the crystals. Sharp peaks at 2575 cm −1 in Kr and 2573 cm −1 in Xe, assignable to hydrogen-bonded S–H, have also been observed. A parallel relationship between the spectral position of isolated H 2 S and the polarizability of the host molecule has been observed.

Photodissociation of H2S doped in low temperature rare gas solids under UV irradiation

Abstract Hydrogen sulfide (H 2 S) doped in rare gas free standing crystals was photodissociated in ultraviolet (UV) region with changing the photolysis laser wavelength. The consumption of H 2 S and appearance of products were pursued by UV and IR absorption measurements. The threshold for the appearance of SH radicals was found to be located between 242 and 248 nm in Kr crystals, which corresponds to the minimum energy of 1.07–1.18 eV for the hydrogen (H) atoms to escape from the initial cage. This value is smaller than the threshold predicted by a sudden exit model, which implies the importance of delayed exit after energy transfer and distortion of the cage. No apparent difference in the threshold energy was noticed between the H atoms produced from the monomer H 2 S and those from the dimer (H 2 S) 2 in the crystal.

The Uptake Coefficient of I2 on Various Aqueous Surfaces

Uptake coefficient of I2 on aqueous surfaces was measured by using an impinging flow method. Dependence of the uptake coefficient on the gas-liquid contact time and pH was investigated. The uptake coefficient was (3.7± 2.0)×10−4 at 120 ms, 293 K and pH = 5.6. In the alkaline region, the uptake coefficient was larger by one order of magnitude than that in the neutral and acidic region. The I2 uptake on KI solutions and synthetic sea water solutions was also measured. According to the analysis by the reactive uptake model, the uptake of I2 was shown to be mainly determined by liquid phase reactions and the accommodation coefficient of I2 on aqueous surfaces was estimated to be 0.01.