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71.
Kishi N Kikuchi S Ramesh P Sugai T Watanabe Y Shinohara H 《The journal of physical chemistry. B》2006,110(49):24816-24821
Photoluminescence (PL) from purified (>90%) double-wall carbon nanotubes (DWNTs), which have been synthesized by zeolite catalyst-supported chemical vapor deposition (zeolite-CCVD), of very small diameters (0.8-nm average inner tube) is reported. The PL contour mappings for various ratios (1-90%) of double- versus single-wall carbon nanotubes by thermal oxidation have enabled us to unambiguously identify the chirality of inner tubes for the DWNTs synthesized. After the extensive high-temperature oxidation at 700 degrees C, high-purity (>90%) DWNTs of approximately 0.8 nm inner diameter are obtained, and most of these correspond to the DWNTs having inner tubes with chiralities of (7,5), (7,6), and (9,4). 相似文献
72.
Nakano M Kishi R Nakagawa N Ohta S Takahashi H Furukawa S Kamada K Ohta K Champagne B Botek E Yamada S Yamaguchi K 《The journal of physical chemistry. A》2006,110(12):4238-4243
The second hyperpolarizabilities of bisimidazole- and bistriazole-benzene compounds have been calculated at different levels of approximation to unravel the effects of diradical character as well as of charge and spin multiplicity. The largest second hyperpolarizabilities are associated with intermediate diradical character, provided positive charging does not compensate for this effect. For the neutral diradical bisimidazole compound, the singlet diradical species possesses a second hyperpolarizability two to three times larger than the corresponding triplet, demonstrating the possibility of spin state control of the third-order NLO responses for diradical species. 相似文献
73.
We study the efficiency at maximum power, η*, of engines performing finite-time Carnot cycles between a hot and a cold reservoir at temperatures Th and Tc, respectively. For engines reaching Carnot efficiency ηC=1-Tc/Th in the reversible limit (long cycle time, zero dissipation), we find in the limit of low dissipation that η* is bounded from above by ηC/(2-ηC) and from below by ηC/2. These bounds are reached when the ratio of the dissipation during the cold and hot isothermal phases tend, respectively, to zero or infinity. For symmetric dissipation (ratio one) the Curzon-Ahlborn efficiency ηCA=1-√Tc/Th] is recovered. 相似文献
74.
[structure: see text] The feasibility of assembling 3JH,H profiles from NMR data collected on relevant, but not necessarily specific, NMR database compounds representing a given stereocluster was demonstrated. By this approach, the 3JH,H profile was created for the contiguous tetraol peracetate stereocluster. The reliability and applicability of the database thus assembled were demonstrated for known peracetates derived from two heptoses. 相似文献
75.
An investigation by high-resolution transmission electron microscopy of the precipitation process during ageing a Cu–1.2?wt%Be–0.1?wt%Co alloy at 320°C has revealed that the transition phases follow a γ″→ γ″?+?γ′?→?γ sequence. The γ′ phase heterogeneously precipitates on the γ″ phase. The effects of an external stress on the nucleation and growth of disc-shaped γ″ and plate-shaped γ′ precipitates have been examined for the alloy aged at 320°C. A compressive stress applied in the [001] direction during ageing preferentially accelerates the nucleation and growth of the γ″ variant normal to the [001] axis among three crystallographically equivalent variants and the specific four γ′ variants formed on the γ″ variant normal to the [001] axis. A tensile stress does not significantly affect those of γ″ and γ′ precipitates. The critical diameter of the disc-shaped γ″ nucleus is estimated as about 1?nm from evaluation of the interaction energy between the applied stress and the misfit strains of γ″ precipitates. It is proposed that applied external stress does not affect the diffusion rate but the interphase boundary velocity. 相似文献
76.
77.
报道了n型掺杂ZnSe/BeTe/ZnSe Ⅱ型量子阱(type-Ⅱ QW)在极低温 (5—10 K)条件下的各种光学性质. 磁场中(Farada配置)ZnSe层的反射光谱展示了一个典型的负的带电激子(X-)的跃迁特征. 对于空间间接光致发光(spacially indirect PL)光谱,它的主发光峰显示了一个反玻尔兹曼分布的非对称性,并且在磁场中(Voigt配置)它的峰值能量随磁场的增加而降低. 这些实验结果显示了该掺杂样品的空间间接PL是来自Ⅱ型QW结构所特有的带电激子的跃迁.
关键词:
光致发光
二维电子气
带电激子
Ⅱ型量子阱 相似文献
78.
Yoshimi Shioya Toshiyuki Ohdaira Ryoichi Suzuki Yutaka Seino Kazuhiko Omote 《Journal of Non》2008,354(26):2973-2982
Plasma-enhanced chemical vapor deposition (PE-CVD) low-dielectric (low-k) film was irradiated with ultra violet (UV) light of wavelength 172 nm to enhance mechanical strength and reduce dielectric constant (k value). The thickness measurement method for the UV annealed low-k film is discussed. The effects of UV irradiation on dielectric constant, shrinkage, stress, density, pore size, mechanical strength, and structure are clarified and the mechanism is discussed. 相似文献
79.
Fine glass particles Na2O–CaO–B2O3–SiO2 are heated on glassy-carbon substrate to obtain micrometer-size solid immersion lenses (μ-SILs), and the composition dependence of the wetting property between glass melt and glassy-carbon substrate is investigated. The obtained glass particles have the super-spherical shapes with smooth surfaces. The contact angles of the particles are ranging from 125° to 147° depending on the glass composition, and there are the compositions at which the shape of the glass satisfies the optical condition of μ-SIL, showing the correlation between the contact angle and the internal structure of the glass. These results revealed that the super-spherical shape of μ-SIL can be controlled by the glass composition through the wetting property. 相似文献
80.