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991.
The structures of propene and 3,3,3-trifluoropropene have been studied by electron diffraction intensities measured in the present study and rotational constants reported in the literature. The following average structures have been determined: For propene, rg(CC) = 1.342 ± 0.002 Å, rg(C-C) = 1.506 ± 0.003 Å, rg(C-H)vinyl = 1.104 ± 0.010 Å, rg(C-H)methyl = 1.117 ± 0.008 Å, ∠(C-CC) = 124.3 ± 0.4°, ∠(CC-H) = 121.3 ± 1.4°, and ∠(C-C-H) = 110.7 ± 0.9°; for trifluoropropene, rg(CC) = 1.318 ± 0.008 Å, rg(C-C) = 1.495 ± 0.006 Å, rg(C-H)= 1.100 ± 0.018 Å, rg(C-F) = 1.347 ± 0.003 Å, ∠(C-CC) = 125.8 + 1.1°, ∠(C-C-F) = 112.0 ± 0.2°, where the valence angles refer to the rav structure, and the uncertainties represent estimated limits of experimental error. A simple set of quadratic force constants for each molecule has been estimated. Regular trends have been observed in the CC and C-C bond distances and the C-CC angles in these and related molecules. Significant differences between the CC, C-C and C-F distances and the C-C-F angle in trifluoropropene and in hexafluoroisobutene reported by Hilderbrandt et al. have been indicated. 相似文献
992.
The phosphorescence spectrum of C3S2 was observed in a low-temperature Ar matrix with excitation of an Ar+ laser. The spectrum consists of a very strong 0-0 band at 18 287 cm?1 and well-resolved progressions in the ν2, ν5, ν6, and ν7 vibrations. Side bands were found on the high-energy sides of some transitions. The separation between the main and side bands is 23 cm?1. Polarization analysis suggests that C3S2 is linear symmetric in the Phosphorescent state as in the ground electronic state. On the basis of symmetry considerations and a qualitative evaluation of spin-orbit coupling, the phosphorescent state is assigned to 3Σu? with Σu+ and Πu components split by spin-spin interaction. The Σu+ level is lower than the Πu one by 23 cm?1 and the main and side band emissions start from the Σu+ and Πu levels, respectively. The Σu+ component seems to acquire allowed character from a 1Σu+ state by spin-orbit coupling and from bent and states by ν5 vibronic coupling. Mixing of the Σu+ and Πu components through ν5 is responsible for most of the side bands. The ν5 frequency is estimated to be 160 ± 20 cm?1 in the 3Σu? state from the intensities of ν5 progression bands and from the ground-state frequency, 411 cm?1. 相似文献
993.
994.
We report the synthesis of alpha-AlReSi and show that it is a 1/1-cubic approximant phase of the icosahedral quasicrystal with a = 12.9 A. The trend of the resistivity of the new approximant phase shows a nonmetallic character, similar to those seen in the stable icosahedral phases. The resistivity depends sensitively on the Re concentration and the nonmetallic transport is observed only at the Re concentration close to 17.4 at. %, where the transition metal sites in the icosahedral cluster are exclusively occupied by Re atoms. In view of a recent ab initio calculation, the present result suggests strongly the formation of the virtual bound states, or confinement of electrons, in the icosahedral clusters of transition metal atoms. 相似文献
995.
A new mode-locking method of tunable dye laser is described. This simple and practical method requires only an external intensity modulator to the pumping source. After the simple analytical considerations, the experimental work was done using an Ar laser pumped Rhodamin 6G dye laser and an acousto-optic modulator. As results, stable continuous trains of mode-locked pulses were obtained throughout in the ordinary lasing range 570–630 nm. The pulse width, estimated to be 30–50 ps by SHG autocorrelation measurements, is limited by the bandwidth of Lyot filter used. It is also shown experimentally that this method can be applicable for the suppression of the growth of double pulses in passive mode-locking with saturable absorber (DODCI). 相似文献
996.
K. Takeuchi O. Kurihara Y. Makide K. Midorikawa H. Tashiro 《Applied physics. B, Lasers and optics》1985,37(2):67-72
A new working molecule 2-bromo-1,1,1,2-tetrafluoroethane is reported for laser isotope separation of tritium. The multiphoton dissociation rate of CF3CTBrF is studied as a function of irradiation wavenumber, using a CO2 or NH3 laser. In a tightly focused irradiation geometry where the dissociation saturates both for CF3CTBrF and CF3CHBrF, their threshold fluences of dissociation and the geometrically biased selectivity are measured near the maximum of the dissociation rate of CF3CTBrF. When the irradiation geometry is optimized, a high selectivity exceeding 2700 is obtained. 相似文献
997.
Guan-Yeow Yeap Elham A. Al-Taifi Chin-Hin Ong Wan Ahmad Kamil Mahmood Daisuke Takeuchi Masato M. Ito 《Phase Transitions》2013,86(6):483-496
A new series of non-symmetric liquid crystal dimers N-(4-(n-(4-(benzothiazol-2-yl)phenoxy)alkyloxy)benzylidene)-4-chloroaniline containing benzothiazole and benzylideneimine units connected by a flexible alkyl spacer, –(CH2) n –, with n ranging from 4 to 12 in even parity have been prepared. All five members of this homologous series exhibit an enantiotropic nematic phase. The compounds with greater n of 8–12 exhibit both nematic and smectic phases upon cooling. A notable feature among this series is that for the member with n?=?10, the smectic–nematic transition is also present. The nematic–isotropic transition temperatures and associated entropy changes with respect to all compounds in this series exhibit a dramatic dependence on the length of the flexible spacer. A comparison of the transitional properties of this series with those of α-(4-benzylidenechloroaniline-4′-oxy)-ω-[4-(thiophene-2-carboxyl)benzylideneaniline-4′-oxy]alkanes reveals that replacing benzothiazole moiety at one side of the flexible alkyl spacer reduces the nematic–isotropic transition temperature. 相似文献
998.
Akihisa Takeuchi Kentaro Uesugi Yoshio Suzuki Seiichi Itabashi Masatoshi Oda 《Journal of synchrotron radiation》2017,24(3):586-594
Fresnel zone plates with apodized apertures [apodization FZPs (A‐FZPs)] have been developed to realise Gaussian beam optics in the hard X‐ray region. The designed zone depth of A‐FZPs gradually decreases from the center to peripheral regions. Such a zone structure forms a Gaussian‐like smooth‐shouldered aperture function which optically behaves as an apodization filter and produces a Gaussian‐like focusing spot profile. Optical properties of two types of A‐FZP, i.e. a circular type and a one‐dimensional type, have been evaluated by using a microbeam knife‐edge scan test, and have been carefully compared with those of normal FZP optics. Advantages of using A‐FZPs are introduced. 相似文献
999.
Fukami Ken Takeuchi Sayaka Fukujyu Tomoya Hagura Yoshio Kawai Kiyoshi 《Journal of Thermal Analysis and Calorimetry》2019,135(5):2775-2781
Journal of Thermal Analysis and Calorimetry - The water sorption, glass transition, and freeze-concentrated thermal transition properties of calcium maltobionate (MBCa)–maltose mixtures were... 相似文献
1000.