Takashi Sumiyoshi

Surface property and catalytic activity of MgOTiO2

The acid-base and reducing properties of MgOTiO2 of various compositions—binary mixtures of a basic oxide (MgO) and an acidic oxide (TiO2)—were studied and compared with their catalytic activities for the decomposition of diacetone alcohol, the dehydration of 4-methyl-2-pentanol, and the alkylation of phenol with methanol. The acidity of TiO2 decreased upon addition of MgO, whereas the basicity of MgO was found to increase upon addition of 10 wt% TiO2. The decomposition rate of diacetone alcohol was correlated well with the basicity of MgO-TiO2 of different compositions, while the dehydration of 4-methyl-2-pentanol was correlated with the acidity. On the other hand, a maximum conversion of the alkylation was observed over MgOTiO2 (weight ratio, 1:1) which has both basicity and acidity. No correlation was found between the reducing property and catalytic activity. The hydrogen exchange reaction of propylene with D2O or D2 over MgOTiO2 (1:1) was shown by microwave spectroscopy to proceed via π-allyl carbanion or isopropyl carbenium ion intermediates, indicating that the active sites are basic and acidic, respectively.

Tracing depositional consequences of environmental radionuclides (137Cs and 210Pb) in Slovenian forest soils

Depth distribution profiles of environmental radionuclides (137Cs and 210Pb) have been investigated in soil to elucidate the underlying environment of semi-natural temperate deciduous and/or coniferous forest soils in Slovenia (Žirovski vrh, Idrija, Kočevski Rog, Pohorie, Gorišnica and Rakitna). Surface enrichment of both nuclides was observed at all the sites investigated in this study, suggesting that the soils had undergone little natural or anthropogenic disturbance for at least the last several decades. Apparent annual burial rates of 137Cs (0.1–0.2 cm y−−1) were estimated to be about 1.3 times higher than those of 210Pb at individual sites of different lithology, which suggests strong affinity of 210Pb to soil organic matter. Variability of the vertical distribution profiles of these nuclides depends not only on “in situ” pedology but also on geographical and meteorological conditions, especially precipitation and wind direction.

Laser Flash Photolysis of Azocumenes. Direct Observation of Stepwise Decomposition

The mechanism of the decomposition of α,α′-azocumene and 2,2′-di-p-tolyl-2,2′-azopropane was studied by means of laser flash photolysis (λ=347 nm) and the optical absorption of 1-methyl-1-phenylethyl (α-cumyl) and α-cumyldiazenyl radicals was observed. The α-cumyl radicals were formed in two modes, a fast mode occurring during the flash and a slow mode after the flash. The ratio of the optical densities pertaining to the two modes depended on the absorbed dose rate. The higher the absorbed dose per flash, the more dominant was the fast mode. The transient band at λ=285 nm which decayed simultaneously with the grow- in of the α-cumyl radicals was assigned to α-cumyldiazenyl radicals. The experimental results strongly suggested the occurrence of the stepwise decomposition mechanism. The dose rate dependent kinetics of the slow formation process was explained in terms of the competition between the unimolecular decomposition and the dimerization of α-cumyldiazenyl radicals. The rate constants of the decompos...

Rate constants for the reactions of benzene-chlorine atom π-complexes with alcohols in carbon tetrachloride

Abstract The reactivity and selectivity of benzene-chlorine atom π-complexes for hydrogen atom abstraction from various alcohols were investigated. Benzene-chlorine atom π-complexes were produced in liquid carbon tetrachloride using the technique of pulse radiolysis at room temperature. The effect of the concentration of benzene and absorbed doses on the formation and decay kinetics were examined and the equilibrium constant of the complex formation was estimated by computer simulation to be 1700 dm 3 mol −1 . The absolute rate constants of the reaction of the π-complexes with various alcohols were measured. Partial reactivities for hydrogen abstraction were estimated based on the observed rate constants. The experimental rate contants could be explained as a sum of the partial reactivities of various types of CH bonds. While the hydrogen abstraction rate constants were one order less than those of free chlorine atoms, higher tertiary/primary selectivities were observed for benzene-chlorine atom π-complexes.

Deprotonation of Poly(4-hydroxystyrene) Intermediates: Pulse Radiolysis Study of Extreme Ultraviolet and Electron Beam Resist

Poly(4-hydroxystyrene) (PHS) has been used in current lithography as a backbone polymer and is also a promising material for EUV and electron beam (EB) lithography. PHS is efficiently deprotonated after the ionization of its radical cation at a low pKa ( 850 kcal/mol).

Dynamics of Radical Cation of Poly(styrene acrylate)-Based Chemically Amplified Resist for Extreme Ultraviolet and Electron Beam Lithography

The dependence of the degree of copolymerization on the dynamics of radical cations of resist polymers was studied. The dynamics of radical cations was investigated in a chemically amplified resist polymer system. In this study, poly(styrene-ran-methyl methacrylate) [P(S–MMA)] was used as the base polymer of the resist model compound. It is suggested that radical cations of MMA are predominantly decomposed to be deprotonated immediately before the hole transfer to the styrene unit in P(S–MMA) at a lower styrene mole fraction ( 70%). It is thus suggested that the hole transfer from the MMA to the multiple styrene units (n > 3) occurs in P(S–MMA).

Estimating emission source of lead using 210Pb specific activity (210Pb/Pb) and zinc as tracers in Slovenian forest soils

Specific activity of 210Pb (210Pb/Pb) is a good indicator for distinguishing local and remote emission sources of Pb deposited on some forest floors in Slovenia. Another parameter (zinc in soil) gives additional information on possible emission sources and distance of Pb transported from the source. The procedure based on 210Pb activity measurements and non-destructive Pb and Zn determination is rather simple, and not necessary any chemical pre-treatments with strong acids. The soils investigated in this study were collected from several temperate forest sites (Žirovski Vrh, Idrija, Kočevski Rog, Pohorje, Gorišnica, Rakitna, Hotavlje, Otovci, Ptujska gora and Puče) in Slovenia where high level of Pb contamination has been known in some places. Regression analyses of the results suggest an applicability of the proposed procedure for estimating emission sources and atmospheric transportation of Pb.

Effect of Ultrahigh-Density Ionization of Resist Films on Sensitivity Using Extreme-Ultraviolet Free-Electron Laser

Extreme-ultraviolet free-electron lasers (EUVFELs) producing intense femtosecond pulse are able to superimpose ion-pair formation induced by a single photon onto the other in the resist polymer degradation. Electron beam resist (ZEP520A) sensitivity was obtained by using 61 nm EUVFEL at different dose densities in order to observe the multiple spur effect in a well-controlled environment. A higher ionization density has been identified to suppress the resist-degradation effectiveness due to the multiple spur effect for the first time. This is explained by two competing effects, namely, spatiotemporal overlap reducing the effectiveness, and high radical concentration enhancing cross-linking efficiency.

Deprotonation mechanism of poly(styrene-acrylate)-based chemically amplified resist

The influence of degree of copolymerization of poly(styrene-ran-methyl methacrylate) [P(S-MMA)] on the deprotonation mechanism for EUV chemically amplified resists were investigated by pulse radiolysis, quantity of the acid yield, and density functional theory methods. The degradation of MMA unit occurs immediately before the hole transfer to the styrene unit in P(S-MMA) in the low PS mole fraction (< 50 %). The hole transfer from MMA unit to styrene units occurred in the high PS mole fraction (> 70 %). It is assumed that the formation of styrene multimer (n > 3) causes the hole transfer.

Fundamental Study on Reaction Mechanisms in Chemically Amplified Extreme Ultraviolet Resists by Using 61nm Free-Electron Laser

For chemically amplified EUV resists, secondary electrons derived from ionization events play a critical role in the sensitization of acid generators. In this study, we show the dependence of acid generation efficiency on dose rate (fluence per pulse duration) by using 61 nm free-electron laser (FEL) light irradiation. The wavelength of 61 nm (20.3 eV) is applied because single incident photon induces only single ionization event, in contrast to the 13.4 nm EUV photon that induces 4.2 ionization events on average. The acid yield efficiency has enhances with decreasing the dose rate. It is suggested that high density ionization enhances the multiple spur effect.