The UV-induced photochemical reactions of pentacarbonyliron with ethene in a low temperature nitrogen matrix were studied by means of the Mössbauer technique. Fe/CO/4/C2H4/ was produced by UV-irradiation of penfacarbonyliron in close proximity to ethene molecules in a pure ethene matrix, or a homogeneous cocondensed matrix. The other products were obtained via thermal reactions with ethene of Fe/CO/4 trapped in stratified matrices.
Molecular orbital calculations were performed to obtain electron density and electric field gradient at the iron nucleus of iron carbonyls Fe(CO)n (n=2–5) so as to estimate the Mössbauer parameters, of these species. The calculated values were compared with the experimental values obtained in low temperature nitrogen matrices; structures of these species were optimized to fit the observed values.
The UV photolysis of pentacarbonyliron isolated in low temperature nitrogen matrix by continuous or pulsed deposition was studied by means of Mössbauer technique. Unstable species such as Fe/CO/n /n=2–4/ were produced by UV irradiation and their Mössbauer parameters were measured. The yields of unstable species were found to be influenced by the deposition method of nitrogen matrix.
Molecular orbital calculations have been performed to obtain the electron density and electric field gradient at the iron nucleus of tetracarbonylethene iron Fe(CO)4(C2H4) produced by UV-irradiation of pentacarbonyliron cocondensed homogeneously with ethene in a low temperature matrix, so as to estimate the Mössbauer parameters of the species. Mössbauer isomer shifts and electron densities at iron nuclei (O) of Fe(CO)n (n=5,4,3,2) as well as Fe(CO)4(C2H4) are discussed: they have fairly good linear relationship to give –0.27 mm/s/aO–3. An isomer of Fe(CO)4(C2H4) produced via thermal reactions of Fe(CO)4 with ethene in a stratified matrix is discussed by comparing the calculated and observed Mössbauer parameters.
Seawater samples were collected from the East China Sea continental shelf and analyzed for 239+240Pu activities. The vertical profiles of 239+240Pu had a similarity for all three stations in the East China Sea. 239+240Pu concentrations were low in the surface layer (3-4 mBq/m3) and increased gradually with depth to become high in the near-bottom layer (7-10 mBq/m3). 239+240Pu concentrations in seawater and the concentrations of suspended particles showed almost the same vertical profiles in the East China Sea continental shelf. The maximum value of 239+240Pu found in the near-bottom layer may be due to the contribution of Pu-rich suspended particles.
Summary Ni1-xZnxFe2O4 (0≤x≤1) mixed ferrite nanoparticles encapsulated with amorphous-SiO2 were prepared by a wet chemical method. Particle sizes were controlled to range from 2.6 to 33.7 nm by heat treatment, and the particle size dependence of saturation magnetization Ms was investigated for the x=0.5 region. The Ms value decreased abruptly for particle sizes below about 6 nm. From the temperature dependence of the magnetization under field-cooled and zero-field-cooled conditions, blocking temperatures Tb were observed to be between 28 and 245 K depending on the particle size. At the blocking temperature, the superparamagnetic spins in the particle are supposed to be blocked against the thermal fluctuation energy. A smaller particle volume causes a lower blocking temperature; so an extremely small particle would be strongly affected by thermal fluctuation.
Mössbauer parameters of tin compounds, Sn(CH3)2H4–n (n=0, 1, 2, 3, 4), isolated in low temperature matrices were related to electronic properties at the tin nuclei obtained by molecular orbital calculations. Structures of novel species, Sn(CH3)2 and Sn(CH3)H, produced via photodissociation of matrix-isolated Sn(CH3)3H and Sn(CH3)2H2, respectively, were determined on the basis of molecular orbital calculations as compared with Mössbauer parameters. The correlations between Mössbauer quadrupole splitting and calculated electric field gradient using STO-3G or MINI-4 were found to depend on the valence of tin atoms because of poor allowance for basis sets in describing highly polar molecules.
Seawater samples were collected from the Yamato Basin and the Tsushima Basin in the Japan Sea and analyzed for their239+240Pu and137Cs concentrations. The concentration of239+240Pu was 7.4 mBq/m3 in the surface water and increased with depth to a maximum value of 38.6 mBq/m3 at 500 m at the Yamato Basin station. The subsurface maximum may be produced by scavenging of239+240Pu in surface water and release of239+240Pu from settling particles. The239+240Pu inventories in the water column were 86.6 and 85.2 Bq/m2 at the two basin stations, suggesting that 90% of239+240Pu delivered to the Japan Sea is still present in the water column.
Unstable novel species produced by photolysis of ferrocene (Cp2Fe) isolated in low-temperature matrix were studied by means of the57Fe Mössbauer spectroscopy. On the UV-irradiation of57Fe-enriched ferrocene co-condensed with CCl4 in low-temperature N2 matrix (20 K), unknown high spin ferrous species (I.S.=0.90±0.01 mm/s, Q.S=1.94±0.02 mm/s) were produced as well as ferricinium ion [Cp2Fe]+ (I.S.=0.52±0.01 mm/s, Q.S.=0.0 mm/s). On the annealing, these photoproducts disappeared to reform ferrocene by the reverse reaction in the matrix. The mechanisms of the photochemical reaction were discussed.
thermally induced structural transformation of a hydrogen-bonded crystal formed
from an amphoteric molecule of 6-[2-methoxy-4-(pyridylazo)phenoxy]hexanoic
acid MeO was studied using differential scanning calorimetry (DSC), Fourier
transform infrared spectroscopy (FTIR) and X-ray diffraction measurement (XRD).
Crystal form of the hydrogen-bonded crystal was measured by single crystal
four circle diffractometer (Mo-Kα radiation). As
a result, the crystal of MeO was stabilized by many C–H⋅⋅⋅O hydrogen
bonds, and the C–H⋅⋅⋅O hydrogen bonds were broken by thermal energy
reversibly. After transformation the supramolecular architecture was composed
of supramolecular polymer including free-rotation pentamethylene main chains.