Masaaki Ogasawara

On the spectral shift of trapped electrons in glassy alcohols irradiated at 4.2 K

Abstract Careful examination of glassy ethanol, and other alcohols for comparison, γ-irradiated at 4.2 K indicates that the initial absorption spectrum of trapped electrons has two components: one is due to IR-absorbing electrons and the other to visible absorbing electrons. Both the electrons are stabilized upon thermal annealing at 77 K independently and slightly, so that their absorption maxima shift to the blue by only (1–2) × 10 3 cm −1 . The apparent large shift of the absorption maximum from the IR to the visible region, observed in the glassy ethanol, is principally due to the selective decay of the IR-absorbing electrons.

Electronic spectra of trapped electrons in organic glasses at 4°K. 3-methylpentane, 3-methylhexane and methylcyclohexane

Abstract The spectra of e − t produced in 3-MP and MCH at 4°K were at longer wavelengths than those at 73°K, and shifted back to the same position as those produced at 73°K when the glasses were warmed to 73°K. The spectra in 3-MHX at 4 and 73°K were the same.

Reaction of solvated electron with poly(methyl methacrylate) and substituted poly(methyl methacrylate) in hexamethylphosphoramide studied by pulse radiolysis

Short-lived reaction intermediates produced by pulse radiolysis of solutions of poly(methyl methacrylate), poly(ethyl methacrylate), poly(n-butyl methacrylate), and poly(isobutyl methacrylate) in hexamethylphosphoramide have been investigated. Immediately after an electron pulse of 20-ns duration, transient absorption spectra which have absorption bands in the UV and in the longer wavelength side of the visible (>600 nm) were observed in all the solutions examined. The former and the latter bands are assigned to the anion radical of the polymers and the solvated electron, respectively. Reactions between the solvated electrons and the polymers and the decay reactions of the polymer anions were studied.

Evolution of the spectra of the localized electrons in glassy alcohols irradiated at 4 K

Abstract Spectra due to localized electrons in glassy ethanol and 1-propanol have been examined by means of the 4 K γ-irradiation technique. The evolution of the spectra, when warmed at 77 K, occurs unexpectedly slowly at a rate dependent on radiation dose. The time-resolved spectra together with the effect of the photobleaching provide a novel interpretation for the evolution of the spectra: (i) initially the spectra comprise of the IR and visible bands due to the electrons localized in distinctly different trapping sites, shallow and deep, (ii) the IR band undergoes a blue-shifting comparatively rapidly by ca. 2 x 103 cm-1, while the visible band shifts slowly by ca.4 x 103 cm-1 when the localized electrons are allowed to relax at 77 K, (iii) in ethanol 40% of the IR absorbing electrons are transformed into the visible-absorbing electrons and contribute to ca. 20% of the peak intensity of the visible band after the spectral evolution, while in 1-propanol the transformation is ca. 30% and contribute to ca. 20% of the relaxed visible band. It is concluded that the evolution of the electron spectra is the most effectively caused by the selective decay of the IR absorbing electrons, though it is attributed partly to both the “digging” and “seeking” mechanisms. Referring the spectra observed from other alcohols and the previous results on the electron scavenging by toluene, the above view seems to be general for glassy alcohols. It is suggested that the visible absorbing electrons are associated with the hydroxyl groups, whereas the IR absorbing electrons are due to the alkyl groups.

Strategic planning of the graduate and undergraduate education in a research university in Japan

As a consequence of the toning down of the University Standards in 1991, many universities in Japan changed their institutional arrangements for undergraduate education. Generally speaking, new curricula put emphasis on specialty programs in each department resulting in relatively weaker general education programs. However, Hokkaido University decided to keep and strengthen the general education programs, which were continuously articulated to each of the specialty programs. The arrangements are a possible model for research universities in Japan of the next generation. In this arrangement the common core curriculum, the essential part of the undergraduate education, is supported by an interdisciplinary education system. The system is “a university in the university” in the sense that it offers a consistent program made of essence of each specialized field abstracted and reorganized for non-specialized students. In contrast, the graduate programs for each department should be more flexible so that they fit the competitive environment in the changing research world. The model is discussed on the basis of the proposals by a task force for strategic planning of Hokkaido University in 21st century.

Anisotropic ESR hyperfine interaction of electrons trapped in crystals of 1,6-hexanediol and 1,8-octanediol

Abstract Localized electrons in irradiated 1,6-hexanediol and 1,8-octanediol have been identified and studied by ESR spectroscopy at 4 K. The spectra show an anisotropic hyperfine structure with couplings less than 35 G due to at least two protons. Spectra recorded from crystals with deuterated hydroxyl groups verify that the trapping site is localized close to a hydrogen bond.

Electron transfer and solvation in 3-methylpentane-1-propanol mixtures γ-irradiated at 77 and 4 K

The trapped electron in 3-methylpentane-1-propanol mixtures γ-irradiated at 77 and 4 K was investigated by observing the evolution of the trapped electron spectra at 77 K by conventional spectrophotometric method. An isosbestic point observed during the spectral evolution indicated that almost all the electrons in 3-methylpentane traps transformed efficiently to those in 1-propanol traps at high concentration of 1-propanol (<0.6 mol dm-3). Results were interpreted in terms of diffusional transfer of the electron or combined diffusion and tunneling mechanism. The electron spectra observed from the mixture irradiated at 4 K were different from the spectra for irradiation at 77 K: the former spectra were due to both shallowly-trapped alcoholated electrons and unrelaxed hydrocarbonated electrons.

On the relaxation of trapped electrons in glassy hydrocarbons irradiated at 4 K

Abstract In contrast to previous reports e−t in 3MHx produced at 4 K shows trap relaxation when warmed to 77 K. The relaxation in 3 MHx and 3MP occurs without loss of e−t, and results in an increase in ϵmax as well as a shift of λmax.

Transfer of electrons from IR to visible traps in 2-methyltetrahydrofuran-methanol mixed glasses irradiated at 4.2 K

Abstract Electrons produced by γ-irradiation at 4.2 K in MTHF-methanol mixed glasses (12, 32, and 50 mole% methanol) have been examined before and after thermal annealing at 77 K. They are localized predominantly in shallow, unrelaxed ethereal traps at 4.2 K and then transfer to deep, relaxed alcoholated traps after annealing at 77 K. At these temperatures the translational motion of the solvent molecules is highly restricted.

Formation and reaction of polymer ions in solutions studied by pulse radiolysis

Abstract Formation and reaction of polymer anions in solutions of poly(methyl methacrylate), poly(ethyl methacrylate), poly(n-butyl methacrylate), poly(isobutyl methacrylate) and poly(4-vinylbiphenyl) in hexamethylphosphorictriamide and 2-methyltetrahydrofuran were studied by nanosecond pulse radiolysis. The rate constants of the reactions of the polymers with solvated electrons were determined and they were compared with those of the corresponding low molecular-weight molecules. Besides, the decay reactions as well as the electron transfer reactions of the anion radicals of these polymers were investigated. The time-profile of the poly(4-vinylbiphenyl) anion observed in 2-methyltetrahydrofuran at room temperature showed a spike which was followed by a slow decay. The fast decaying component was tentatively attributed to geminate recombinations within micro domains in the solution where the polymers were entangled.