Jun Miyazaki’s research while affiliated with Tokyo Denki University and other places

The ⁵⁷Fe Mössbauer spectrum obtained after ⁵⁷Mn (T1/2 = 1.45 min) implantation of solid hydrogen was measured at 7 K. The spectrum was analyzed as three components, and the chemical species of each component was assigned from the obtained Mössbauer parameters and the results of density functional theory (DFT) calculations. The formation process of chemical species and the oxidation states of Fe atoms produced by β– decay of ⁵⁷Mn are discussed considering the charge transfer process, in relation to previous emission Mössbauer spectroscopy experiments with ⁵⁷Co implantation of solid hydrogen at low temperature.

In-beam Mössbauer spectra of ⁵⁷Mn implanted into LiAlH4 were measured at different temperatures between 17 and 300 K. The Mössbauer spectrum measured at 17 K showed two sets of doublets, which were assigned to ⁵⁷Fe atoms at substitutional sites at Al³⁺ and Li⁺ sites. The Debye temperatures θM for the ⁵⁷Fe atoms at Al³⁺-substituted and Li⁺-substituted sites were estimated to be 194 K and 117 K, respectively. The assignments were confirmed by density functional theory calculations.

To investigate the interactions of ⁵⁷Fe atoms with sulfur hexafluoride SF6 molecules, in-beam Mössbauer spectra were measured for ⁵⁷Mn implanted SF6 at 9 K and 65 K. Isolated ⁵⁷Fe atoms or ions produced by β-decay were not trapped within the SF6 matrix. At 9 K, monomeric FeF2 and FeF3 molecules were produced by reaction of ⁵⁷Fe with F atoms released by decomposition of the SF6 molecules. When the temperature of the SF6 solid was increased to 65 K, FeF4 was formed in addition to FeF2 and FeF3. Density functional calculations were performed to confirm the assignments of the candidate species identified in the Mössbauer spectra.

Infrared spectra of the photochemical products of bis(cyclopentadienyl)dicarbonyl titanium, TiCp2(CO)2, isolated in an Ar matrix and a N2 matrix were measured. UV-irradiation of TiCp2(CO)2 produced TiCp2(CO) in the Ar matrix, and three types of nitrogen-containing compounds, TiCp2(CO)(N2), TiCp2(N2), and TiCp2(N2)2 were produced in the N2 matrix. The yields of the species changed with the duration of UV-irradiation. Annealing of the sample resulted in the disappearance of unstable TiCp2(N2) and an increase of TiCp2(N2)2. Isotope shifts of the infrared spectra were measured using ¹⁵N2 to confirm the assignments. The structures of the species were estimated using a double hybrid density functional theory calculation (mPW2PLYP/cc-pVTZ), and the calculated infrared frequencies were in very good agreement with the experimentally measured spectra.

Tris(cyclopentadienyl)ytterbium (YbCp3) was isolated in solid argon matrices, and the monomeric structure of YbCp3 was studied by means of infrared spectroscopy and density functional theory calculations. Compared with our previous study on the structure of tris(cyclopentadienyl)scandium (ScCp3) isolated in solid argon matrices, it was apparent that the monomeric structure of YbCp3 has three η5-Cp bonds to the Yb atom, Yb(η5-Cp)3, analogous to the structure of matrix-isolated ScCp3. In addition, the stable dimer structures of YbCp3 were also predicted using density functional theory calculations. Furthermore, we produced the acetone adduct molecules of YbCp3 for the first time by co-condensing YbCp3 and an acetone/argon mixture gas on a cold substrate at 20 K. Molecules with Yb-O bonding between YbCp3 and acetone were detected in low-temperature acetone/argon matrices. By using natural bond orbital (NBO) and curve fitting analysis, the structures of the acetone adduct molecules of YbCp3 were deduced.

We report the in-beam Mossbauer spectra of Mn-57 implanted into polycrystalline lithium hydride (LiH). Comparing the in-beam Mossbauer spectra data with the results of density functional theory (DFT) calculations, Fe-57 atoms were implanted into Li or H substitutional sites in the LiH crystal. By changing the sample temperature from 11 K to over 800 K, we observed a reduction of Fe-57 at a substitutional H site with a neighboring Li or H atom defect, and an addition of Fe-57 at substitutional H or Li site without neighboring atom defects. It suggests annealing effect-induced recovery.

We measured the temperature dependence of 57Fe Mössbauer spectra obtained after 57Mn implantation into polycrystalline LiH with an extremely low implantation dose. Density functional calculations suggested that the Fe atoms were predominantly implanted into both Li and H substitutional sites of the LiH crystal.

Laser ablation of copper metal in water was performed in order to obtain copper oxide particles. Scanning electron microscopy, energy dispersive X-ray fluorescence spectrometry, transmission electron microscopy, and electron diffraction were conducted in order to determine the size, shape and structure of the particles. The source of the O atoms in the copper oxide particles is the surrounding water molecules. The copper oxide particles obtained by laser ablation were both crystalline and amorphous. The crystalline particles were determined to be paramelaconite Cu4O3.

Tris(cyclopentadienyl)scandium ScCp3 was isolated in Ar-matrices (20K) and the structure of monomeric ScCp3 was studied using infrared spectrometry. When compared with the spectra and results of density functional calculations, the matrix-isolated ScCp3 was found to have a structure where all three of the cyclopentadienyl rings coordinate to scandium in η5 coordination, Sc(η5-Cp)3, which is different from the structure in the solid phase. Moreover, a stable dimer structure was estimated to be [(η5-Cp)2Sc(μ-η1-Cp:η1-Cp)]2, using density functional calculations.

The photochemistry of cyclopentadiene isolated in low-temperature argon matrices was studied by means of IR and UV/VIS spectroscopy. Bicyclo[2.1.0]pent-2-ene was formed by the irradiation of matrix-isolated cyclopentadiene using a super-high-pressure mercury lamp. When the matrix-isolated cyclopentadiene was irradiated with shorter wavelength using a low-pressure mercury lamp, further reactions of bicyclo[2.1.0]pent-2-ene were found to produce allylacetylene and vinylallene. While the photochemistry of cyclopentadiene to form bicyclo[2.1.0]pent-2-ene is known in a solution system, the production of allylacetylene and vinylallene in a matrix-isolated system has never been previously reported. The assignments of the species and the determination of the reaction mechanisms were performed using molecular orbital calculations.