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921.
Mitsutoshi Kayashima Nobuo Sano Yukio Matsushita 《Journal of Physics and Chemistry of Solids》1983,44(12):1147-1155
An EPR absorption was detected in the system CaO-SiO2-Al2O3 doped with sulfur. The signal consisted of six isotropic hyperfine lines and demonstrated isotropic fine structure and forbidden doublets. The signal was attributed to an Mn2+ impurity displacing Ca2+ in fine CaS crystallites formed in the matrix of the ternary system. The spectrum was well accounted for with the parameters g = 2.0021 ± 0.0001 and A = ?77.1 ± 0.6 × 10?4 cm?1. Sample preparation conditions did not affect the hyperfine splitting, although the fine structure and forbidden lines proved to be dependent on the conditions of preparation. It is suggested that the appearance of the fine structure is a result of the second effect of the hyperfine structure when the cubic field parameter a approaches zero and, consequently, the structure is free of superposition caused by an anisotropic shift determined by a. We ascribe the change in fine structure to the variation in a and discuss the nature of the energy splitting of the state in a cubic field. We also note a correlation between the fine structure and the forbidden lines. This finding suggests that a is not necessarily specific to the host lattice and, furthermore, that the consideration of superposition of axial or lower symmetry upon the original cubic field of the central Mn2+ ion is vital for the determination of a. 相似文献
922.
923.
924.
Akihiko Ueno Fujio Toda Yoshio Iwakura 《Journal of polymer science. Part A, Polymer chemistry》1974,12(8):1841-1849
Poly(γ-1-naphthylmethyl L - and DL -glutamate) (PNLG and PNDLG) and copolypeptides of γ-1-naphthylmethyl L -glutamate and γ-benzyl-L -glutamate were used as sensitizers for isomerization of trans-1,2-diphenylcyclopropane. Quantum yields relative to that of 1-methylnaphthalene were measured in dichloroethane (DCE) and dichloroacetic acid (DCA). The relative quantum yield in DCE was smaller than unity for PNLG, but greater than unity for PNDLG and copolypeptides. The result is discussed in terms of increased effective collisional radius and energy trapping by excimer formation. The relative quantum yields in DCA were close to unity except for the copolypeptides of higher γ-benzyl L -glutamate content. This suggests that the naphthalene groups act in the same manner as their monomeric counterparts in the random conformation and that the greater proportion of γ-benzyl L -glutamate in the copolypeptides lowers the quantum efficiency because trans-1,2-diphenylcyclopropane must penetrate through the polymeric medium in order to encounter the excited naphthalene. 相似文献
925.
926.
Kohei Morioka Yoshikatsu Suito Yutaka Isobe Shigeki Habaue Yoshio Okamoto 《Journal of polymer science. Part A, Polymer chemistry》2003,41(21):3354-3360
The radical polymerization of an optically active methacrylamide, N‐[(R)‐α‐methoxycarbonylbenzyl]methacrylamide, was carried out in the absence and presence of Lewis acids such as yittribium trifluoromethanesulfonate [Yb(OTf)3] and scandium trifluoromethanesulfonate [Sc(OTf)3]. Catalytic amounts of the Lewis acids significantly affected the stereoregularity of the obtained polymers. The polymerization with Yb(OTf)3 in tetrahydrofuran afforded isotactic polymers (up to mm = 87%), whereas the conventional radical method without the Lewis acid produced polymers rich in syndiotacticity (up to rr = 88%). The radical polymerization in the presence of MgBr2 proceeded in a heterotactic‐selective manner (mr = 63%). Thus, the isotactic, syndiotactic, and heterotactic poly(methacrylamide)s were synthesized by the radical processes. The chiral recognition abilities of the obtained optically active poly(methacrylamide)s were affected by the stereoregularity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3354–3360, 2003 相似文献
927.
Takumi Goto Satoshi Matsuyama Hiroki Nakamori Yasuhisa Sano Yoshiki Kohmura Makina Yabashi 《Synchrotron Radiation News》2016,29(4):32-36
Ultra-bright and high-coherence X-rays are now being used in synchrotron radiation facilities and X-ray free electron laser facilities. X-ray focusing techniques are essential to take full advantage of these excellent X-ray light sources. To meet the strong demand, high-quality X-ray focusing optics have been developed owing to the advancement of ultraprecision machining and measurement. State-of-the-art refractive lenses [1], zone plates [2], and Laue lenses [3] can be used to achieve X-ray focusing to a spot a few tens of nanometers. 相似文献
928.
Yasuhiro Yamada Kenichi Tanabe Naoki Nishida Yoshio Kobayashi 《Hyperfine Interactions》2016,237(1):105
Iron films were deposited on porous alumina substrates using an arc plasma gun. The pore sizes (120 – 250 nm) of the substrates were controlled by changing the temperature during the anodic oxidation of aluminum plates. Iron atoms penetrated into pores with diameters of less than 160 nm, and were stabilized by forming γ-Fe, whereas α-Fe was produced as a flat plane covering the pores. For porous alumina substrates with pore sizes larger than 200 nm, the deposited iron films contained many defects and the resulting α-Fe had smaller hyperfine magnetic fields. In addition, only a very small amount of γ-Fe was obtained. It was demonstrated that the composition and structure of an iron film can be affected by the surface morphology of the porous alumina substrate on which the film is grown. 相似文献
929.
A tunable supramolecular phenylacetylene host system with a chiral channel-like cavity is developed by using (1R,2S)-2-amino-1,2-diphenylethanol. This host system possesses a chiral 21-helical columnar structure; chiral cavities are constructed by the self-assembly of the 21-helical column, and guest molecules are included by varying the packing of this column. 相似文献
930.
Wang W Bando Y Zhi C Fu W Wang E Golberg D 《Journal of the American Chemical Society》2008,130(26):8144-8145
Noncovalent functionalization of boron nitride nanotubes (BNNTs) in aqueous solution was achieved by means of pi-stacking of an anionic perylene derivative, through which carboxylate-functionalized BNNTs were prepared for the first time. Starting from the functionalized nanotubes, an innovative methodology was designed and demonstrated for the controlled near-surface carbon doping of BNNTs. As a result of such delicate doping, novel B-C-N/BN coaxial nanotubes have been fabricated, and their p-type semiconducting behaviors were elucidated through gate-dependent transport measurements. 相似文献