Hitoshi Yamaoka

Energetics of the Collision-Induced Dissociations C2H2+→C2H+ + H and C2H2+→H+ + C2H

The energetics of the collision-induced dissociation of fast C2H2+ ions into C2H+ + H and H+ + (C2H) are determined from the measurements of the translational energy of the fragments and from the study of the influence of ionizing electron energy, incident ion energy, delay between production of the ions and collision, and nature of the target used. Evidence is given for the occurrence of three different processes: (i) electronic excitation to a dissociative state, (ii) adiabatic dissociation following momentum transfer, and possibly (iii) collision-induced predissociation, processes (i) and (iii) giving rise to C2H+ + H and process (ii) to H+ + C2H. The adiabatic correlations between the states of C2H2+ ions and of their fragments are discussed.

Cryogenic properties of polymers

Abstract The cryogenic properties of polymers are recently drawing attention with new developments in space, superconducting magnet and electronic technologies. Requirements for polymeric materials used in cryogenic environments are extremely severe and complicated. Research aimed at meeting these requirements is focused in two directions: one concerns the physical properties of polymers at cryogenic temperatures, while the other is concerned with the unique characteristics of polymeric materials for cryogenic applications. The objective of this article is to review the thermal properties and the relaxational behavior of polymers at cryogenic temperatures, the relationship between functionality and the cryogenic relaxation of guest molecule — polymer matrix systems, and the survey of polymeric materials for various cryogenic applications.

Mossbauer Spectroscopic Study of Iodine-Doped Polyacetylene

The Mossbauer spectroscopy has been applied to iodine-doped polyacetylene employing 129 I. It is found that the polymer films contain I - , I 3 - and I 5 - with symmetrical charge population, where the content of each iodide anion depends on the doping level. Under dynamic evacuation, it is elucidated that I 5 - converts to I 3 - by the elimination of I 2 from I 5 - . The variation of electrical conductivity in iodine-doped polyacetylene is discussed with the mechanism of charge transfer from the polymer and with the mutual conversion of iodide anions.

An 129I Mössbauer spectroscopic study of iodine doped in poly(vinylpyridines)

The charge densities and the configurations of iodine doped in poly(2‐ and 4‐vinylpyridines) have been studied by using the Mossbauer effect of 129I at 16 K. The ’’outer complex’’ is first formed in the system of poly(2‐vinylpyridine) and iodine. The extent of the charge transfer is estimated to be 0.22 in the outer complex, which is nearly the same as pure pyridine. The iodine of the outer complex varies gradually to the tri‐iodide anion and then to the iodide anion by accepting electrons from the pyridine ring of the polymer. In the system of poly(4‐vinylpyridine) and iodine both the outer complex and the ’’inner complex’’ are first observed, and the iodine species in these complexes vary gradually to the I3− ion and finally to the I− ion in a similar manner as the system of poly(2‐vinylpyridine) and iodine. From the values of the Mossbauer parameters the charge or electron populations of the iodine species are calculated, and the arrangements of these species are discussed.

Mössbauer spectroscopic study on polyacetylene doped with iodine

Abstract The 129 I Mossbauer effect has been applied to polyacetylene films of cis -(CHI 0.23 ) x as prepared and cis -(CHI 0.20 ) x led under dynamic evacuation. It has been clarified that both films contain linear I − 5 and I − 3 with symmetric charge population and that the fraction of I − 3 increases after evacuation. The mechanism of electrical conductivity in iodine-doped polyacetylene has been discussed on the basis of the chemical form and the dynamic behavior of the anion species.

Cryogenic properties of engineering plastic films

The mechanical and dielectric properties of several engineering plastic films were measured at cryogenic temperatures. The tensile strength and elongation of polyethylene-2,6-naphthalenedicarboxylate at 77 K were found to decrease with an increase in the degree of crystallinity. The peak height of dielectric loss around 230 K of this polymer also decreased with increasing degree of crystallinity, indicating that this peak is closely associated with motion in an amorphous region of the polymer. The cryogenic properties of two kinds of newly developed polyimide films were also studied. On the basis of the results obtained, the relationship between the chemical structures of polymers and their cryogenic properties are discussed.

Anionic ring-opening polymerization of silacyclobutane derivatives

Anionic polymerizations of 1,1-dimethylsilacyclobutane, 1,1-diethylsilacyclobutane and 1-methyl-1-phenylsilacyclobutane were investigated. Addition of 5 mol % of butyllithium to a solution of 1,1-dimethylsilacyclobutane in THF-hexane (1 : 1) at −48°C provided poly(1,1-dimethylsilabutane) in 99% yield. Mn and Mw/Mn of the obtained polymer were 2400 and 1.10. This polymerization proceeded with a living nature. Mn increased in proportion as the yield of polymer increased. Addition of the second fresh feed of the monomer to the reaction mixture restarted polymerization of the second monomer at the same rate as in the initial stage. Addition of styrene to the living poly(1,1-dimethylsilabutane) provided a poly(1,1-dimethylsilabutane-b-styrene) block copolymer. It was also found that a polymerization of 1,1-diethylsilacyclobutane in THF-hexane at −48°C showed a living nature. In contrast, a polymerization of 1-methyl-1-phenylsilacyclobutane in THF at −78°C did not show a living nature.

X‐ray optics research and development for SPring‐8 beamlines

X‐ray optics research and development for SPring‐8 beamlines are described. These include standard developments of monochromators, high‐heat load optics, wide energy‐range monochromators for bending beamlines, long x‐ray mirrors, and single and graded d‐spacing synthetic multilayers.

Correlative multielectron processes in K-shell photoionization of Ca, Ti and V in the energy range of 8-35 keV

The Kalpha satellite spectra arising from the correlative multielectron processes accompanying K-shell photoionization of Ca, Ti and V were measured using a broad range crystal spectrometer. Multiconfiguration Dirac-Fock calculations were performed to interpret the observed,x-ray energies and the spectral line shape., The calculations agree fairly well with the experimental results. The variation of the KalphaL(1) satellite and the Kalpha(1,2)(h) hypersatellite intensities was measured as a function, of excitation energy in the range of 8-35 keV. The KalphaL(1)/Kalpha(1,2) intensity ratio for each,element is already saturated in our energy range, and the asymptotic values of 1.58 +/- 0.08, 1.26 +/- 0.06 and 0.97 +/- 0.05% for Ca, Ti. and V were determined. By combining the present results and the previously measured values for various elements, we have found a Z(-3.5) scaling law for the KalphaL(1)/Kalpha(1,2) intensity ratio, The measured Kalpha(1,2)(h)/Kalpha(1,2) for each element, is found to increase smoothly from its onset and shows a long saturation range extending up to at least 25 keV above the threshold for Ti. The evolution of the Kalpha(1,2)(h)/Kalpha(1,2) intensity ratio is compared with the analytic Thomas model and with the theoretical calculation based on the screened hydrogenic model. (Less)

Effect of counterion species on the dynamics of polystyrenesulfonate in aqueous solution as studied by dynamic light scattering

The diffusion behavior of macroions in aqueous solutions especially at low salt concentrations has been interesting and also mysterious problem since Schurr et al. found slow mode in 1978. By the systematic investigations on the structure and dynamics of charged particles and macromolecules in solution, it has been suggested that some novel factor(s) should be taken into account for understanding of interesting phenomena in these systems. In this study, the dynamic character, i.e., diffusion behavior of polystyrenesulfonate (PSS) in aqueous solution has been studied by dynamic light scattering (DLS) as a function of salt concentration in various salt forms. Both fast and slow modes were clearly detected. With increasing salt concentration, the fast mode became dominant and its decay rate became slower. On the other hand, the slow mode was not so sensitive to salt concentration but its contribution markedly decreased with increasing salt concentration and then became almost negligible at higher salt concen...