Toshiyuki Oyama

Cold Jet Infrared Absorption Spectroscopy: The ν3 Band of UF6

The ν3 band of UF6 is studied at a low rotational and vibrational temperature using a tunable diode laser. Infrared absorption in a pulsed supersonic free jet of UF6 is observed by phase sensitive detection synchronized with the pulse frequency. Absorption lines from P(21) to R(27) are measured for 238UF6 with a Doppler limit resolution. Only Q-branch peaks are observed for 235UF6 using naturally abundant isotopic species. Isotope shift for the ν3 band is determined to be 0.6040 cm-1.

Laser-assisted exfoliation of potassium-ammonia-graphite intercalation compounds

Potassium-ammonia-graphite intercalation compounds (K-NH3-GIC) synthesized from small natural graphite particles from China were rapidly heated by a cw-Nd:YAG laser beam (1.056 μm) in an Ar purge environment to yield exfoliated small graphite particles as sources for electrical conductive films. The laser heating method was demonstrated to be effective for exfoliation of K-NH3-GIC prepared from natural graphites in sizes of under 37 μm, 37 ~ 63 μm and 63 ~ 88 μm, whereas no exfoliation of these graphites occurred by either gas burner heating or electric furnace heating. The results also show that K-NH3-GIC prepared from natural graphite 350 ~ 500 μm in size was exfoliated to 32-fold of the volume of feed natural graphite. This exfoliation ratio is 2.6 times larger than the ratio obtained by the gas burner heating method.

Effect of exfoliation ratio on the flakiness of fine graphite particles obtained by grinding of exfoliated graphite.

In this study, we ground exfoliated graphite and investigated the flakiness of the ground products using the previously reported particle size measurement techniques

Isotopically selective infrared multiple-photon dissociation of MoF6 by a H2-raman laser

Infrared multiple-photon dissociation (IRMPD) of MoF6 has been investigated with a parallel beam of a para-H2 Raman laser newly developed by our group. MoF6 gas (2 Torr, natural abundance) was put into in a static cell cooled to −58℃ and was irradiated with the laser line at 728 cm−1. The critical fluence of 0.11 Jcm−2 for complete dissociation was determined by analysis with a Gaussian beam model. Irradiation at the lower frequency side (728 cm−1) of the MoF6 ν3 band enriched the lighter isotopes in the residue. A maximum value for selectivity of 1.1 was obtained.

Particle Formation by CO2 Laser-Induced Breakdown. (II). Formation of B4C Fine Powder from Boron Bromide-Methane-Hydrogen System.

Fine B4C powder was synthesized by the TEA-CO2 laser-induced dielectric gas breakdown of a BBr3 + CH4 + H2 gas mixture. The product was characterized by SEM, ICP atomic emission spectroscopy, and electron and X-ray diffractions. The particles show a narrow size distribution with a mean particle size of 0.18 μm. The yield of particles was increased linearly with increasing laser pulse energy. About 90% of incident pulse energy was absorbed by plasma in the reactant gas.