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51.
52.
The measurement of 81Br NQR in CH3NH3HgBr3 has been carried out in the temperature range between 80 and 300 K using a pulse NQR method. The temperature dependence of 81Br NQR frequencies in CH3NH3HgBr3 has revealed that it undergoes three characteristic successive phase transitions at T?=?123, 184 and 239 K. The phase transition temperature at T?=?239 K is the second-order type, whereas those at T?=?184 and 123 K are the first-order nature of the phase transitions. Each phase transition seems to be closely related to the motions of methyl ammonium cation as a partial or whole. The enhancement of 1/T 1 at T?=?239 K indicates the onset of the molecular motion of the cation as a whole with increasing temperatures. 相似文献
53.
Hiromitsu Terao Yoshihiko Kai Kazuyo Kita Yoshihiro Furukawa 《Hyperfine Interactions》2010,198(1-3):93-101
The crystals of 4-NH2PyHSbI4 (Py = C5H4N) have been investigated by means of 127I NQR, 1H NMR T 1 and DTA. The crystals can exist in two modifications of β and α(I) at room temperatures. The α(I)-phase is a metastable state which is obtained when the stable β form is heated. The α(I)-phase undergoes a first-order type phase transition of α(I) $\leftrightarrow \alpha $ (II) at 272 K (on heating), while the β-phase is stable down to 77 K. Four and two 127I (m = ±1/2 $\leftrightarrow \pm $ 3/2) NQR lines have been found for the β- and α(II)-phases, respectively. One half of them is assignable to the terminal I atom(s) and the other to the bridging I atom(s) in each phase. All the resonance lines of the α(II)-phase underwent a disappearance above ca. 240 K and no resonance line was observed in the α(I)-phase. The second moment M 2 value of 1H NMR spectra with 8 G2 at 290 K shows that the 4-NH2PyH?+? cations reside in the rigid lattice in the β-phase. In contrast, in the α(I)-phase the cation rotates about an axis more symmetric than pseudo threefold axis. The activation energy of 21 kJ mol???1 was estimated for the reorientational motion in the α(I)-phase from the 1H NMR T 1 measurements. The nature of phase transitions in the 4-NH2PyHSbI4 is discussed in comparison with that in 4-NH2PyHSbBr4. 相似文献
54.
Summary: We developed a new method for synthesizing an organic-soluble permethylated cyclodextrin-based insulated molecular wire (IMW); this method involves the polymerization of a symmetrical linked inclusion complex as a monomer. This monomer was synthesized by dimerization of linked inclusion complexes at the terminal alkynyl groups by Glaser coupling. The polyrotaxane thus obtained is highly soluble in a variety of organic solvents and has a high covering ratio, regioregularity, and photoluminescence efficiency. 相似文献
55.
We study cohomology with coefficients in a rank one local system on the complement of an arrangement of hyperplanes . The cohomology plays an important role for the theory of generalized hypergeometric functions. We combine several known results to construct explicit bases of logarithmic forms for the only non-vanishing cohomology group, under some nonresonance conditions on the local system, for any arrangement . The bases are determined by a linear ordering of the hyperplanes, and are indexed by certain ``no-broken-circuits" bases of . The basic forms depend on the local system, but any two bases constructed in this way are related by a matrix of integer constants which depend only on the linear orders and not on the local system. In certain special cases we show the existence of bases of monomial logarithmic forms.
56.
We report a novel method for manipulation of single giant DNA molecules under a video microscope. Using optically driven microstructures, we manipulated chromosomal DNA of length in the order of millimetres, extended by electroosmotic flow without DNA breakage in aqueous solution: we picked up DNA, using microfabricated hooks and wound it around microfabricated bobbins. 相似文献
57.
58.
A new solid-state NMR pulse sequence for recoupling 13C–1H dipolar interactions under magic-angle spinning is proposed, which works under a spinning speed of a few to several tens kilohertz. The sequence is composed of two different frequency switched Lee–Goldburg sequences, and the modulation of the spin part of the 13C–1H dipolar interaction is introduced by a virtual pulse sequence consisting of unitary operators connecting the rotating frame and the tilted rotating frame. When the cycle time of the spinning is equal to or twice the cycle time of the sequence, the 13C–1H dipolar interactions can be recoupled. The sequence is insensitive to experimental imperfections such as rf inhomogeneity or frequency offset, and the resulting lineshape can be represented by a simple analytical equation based on the zeroth-order average Hamiltonian. Experimental results for [2-13C]
-valine·HCl are reported. 相似文献
59.
Masahide Tona Hirofumi Watanabe Satoshi Takahashi Nobuo Yoshiyasu Toshifumi Terui Chikashi Yamada 《Surface science》2007,601(3):723-727
Using scanning tunneling microscopy (STM) and time of flight secondary ion mass spectrometry (TOF/SIMS), we observed radiation effects on a Si(1 1 1)-(7 × 7) surface in the collision of a single highly charged ion (HCI) with a charge state q up to q = 50. The STM observation with atomic resolution revealed that a nanometer sized crater-like structure was created by a single HCI impact, where the size increased rapidly with q. The secondary ion yields also increased with q in which multiply charged Si ions (Sin+) were clearly observed in higher q HCI-collisions. The sputtering mechanism is briefly discussed, based on the so-called Coulomb explosion model. 相似文献
60.
Kazuo Watanabe Yoshiyasu Matsumoto Margarethe Kampling Katharina Al-Shamery Hans-Joachim Freund 《Angewandte Chemie (International ed. in English)》1999,38(15):2192-2194
The mean size of the Pd clusters deposited on an Al2O3 thin film influences the efficiency of photodissociation of CD4 into CD3 and D as well as the photodesorpion upon irradiation with 193-nm laser light. The picture shows the degree of desorption on Pd clusters of various sizes (as well as on a Pd(111) single-crystal surface) as a function of temperature; the values given refer to the average thickness of the evaporated metal layer. 相似文献