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991.
The dielectric and elastic properties of liquid crystals (LCs) generally depend on the molecule structure, such as polar group and carbon chain length. For further investigation of the influence of molecular structure on the dielectric and elastic properties of fluorine-containing tricyclic isothiocyanate LC, the experimental temperature was controlled at 25°C by precision hot stage, and a precision LCR meter was used to measure the capacitance of six LC cells under the voltage from 0.1 to 20 V at 1 kHz. An LC cell capacitance model and a dual-cell model were adopted to obtain the dielectric anisotropy, and the capacitance–voltage curves of six LC materials were plotted. The threshold voltage of Fréedericksz transition was analysed, and a finite difference iterative method was used to attain specific values of three elastic constants. The influence of molecular structure on the dielectric and elastic constants was finally analysed. Experimental results showed that the introduction of meta-difluoro group would increase the dielectric anisotropy and reduce the threshold voltage of LC. As the length of the alkyl carbon chain increased, the dielectric anisotropy would have an odd–even alternation effect, which would lead to changes in the elastic constants of LC. 相似文献
992.
Wei-Xiu Pang Hong-Ye Wu Jian-Jun Zhao 《Phosphorus, sulfur, and silicon and the related elements》2019,194(1-2):69-75
The anharmonic force field and spectroscopy constants for CH2PCl are determined using CCSD(T), VPT2, and density functional theory employing cc-pVQZ basis sets. The molecule structure, rotational spectroscopic constants, and vibrational wave numbers are compared with the available experimental data. Anharmonicity constants, vibration-rotation interaction constants and cubic force constants are predicted. Vibrational wave numbers and rotational constants for CD2PCl are also determined using the same levels. The isotopic shifts of vibrational wave numbers are remarkable by D atom substitution for 1-chlorophosphaethene. 相似文献
993.
994.
Ling Wu Xiaohua Yang Yangqin Chen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(9):1586-1589
Thirty-four rovibronic spectral lines of the Ω=1/2 component of the (4, 8) band in the A-X system of 35Cl2+ were observed in the range of 16,940-17,010 cm−1, employing optical heterodyne-enhanced velocity modulation spectroscopy. Nonlinear least-squares fitting the effective Hamiltonians results in precise band origin and other molecular constants of the levels involved. 相似文献
995.
A high resolution (0.0018 cm−1) Fourier transform instrument has been used to record the spectrum of an enriched 34S (95.3%) sample of sulfur dioxide. A thorough analysis of the ν2, 2ν2 − ν2, ν1, ν1 + ν2 − ν2, ν3, ν2 + ν3 − ν2, ν1 + ν2 and ν2 + ν3 bands has been carried out leading to a large set of assigned lines. From these lines ground state combination differences were obtained and fit together with the existing microwave, millimeter, and terahertz rotational lines. An improved set of ground state rotational constants were obtained. Next, the upper state rotational levels were fit. For the (0 1 0), (1 1 0) and (0 1 1) states, a simple Watson-type Hamiltonian sufficed. However, it was necessary to include explicitly interacting terms in the Hamiltonian matrix in order to fit the rotational levels of the (0 2 0), (1 0 0) and (1 0 1) states to within their experimental accuracy. More explicitly, it was necessary to use a ΔK = 2 term to model the Fermi interaction between the (0 2 0) and (1 0 0) levels and a ΔK = 3 term to model the Coriolis interaction between the (1 0 0) and (0 0 1) levels. Precise Hamiltonian constants were derived for the (0 0 0), (0 1 0), (1 0 0), (0 0 1), (0 2 0), (1 1 0) and (0 1 1) vibrational states. 相似文献
996.
The Fourier transform gas-phase infrared spectrum of pyrrole, C4H5N, has been recorded with a resolution of ca. 0.003 cm−1 in the 900-1500 cm−1 spectral region. Four fundamental bands, ν8(A1; 1016.9 cm−1), ν23(B2; 1049.1 cm−1), ν7(A1; 1074.6 cm−1), ν20(B2; 1424.4 cm−1) and the overtone band 2ν16(A1; 962.7 cm−1) have been analysed using the Watson model. The ν8 and 2ν16 bands are unperturbed; the ν7 and ν23 bands are locally perturbed, while the ν20 band is globally perturbed by weak c-Coriolis resonance. Upper state vibrational term values, and rotational and centrifugal distortion constants, have been obtained from fits using S-reduction and Ir-representation as well as A-reduction and IIIr-representation. A set of ground state rotational and centrifugal distortion constants using A-reduction was obtained from a simultaneous fit of ground state combination differences from all five bands and previous microwave and millimetre-wave data. 相似文献
997.
The direct observation and rotational analysis of the (3, 6) band in the comet-tail (A2Πi-X2Σ+) system of CO+ are carried out for the first time employing optical heterodyne and magnetic rotation enhanced velocity modulation spectroscopy. That 193 lines are assigned to this band ranging from 12 100 to 12 370 cm−1 results in most accurate molecular constants by nonlinear least-squares fitting procedure employing the effective Hamiltonians. 相似文献
998.
With the values of parameters obtained from improved ligand-field theory, by taking into account all the irreducible representations and their components in EPI as well as all the levels and the admixtures of basic wavefunctions within d^3 electronic configuration, the R-line thermal broadenings (TB) of both MgO:Cr^3+ and MgO:V^2+ have microscopic-theoretically been calculated, The results are in very good agreement with the experimental data. It is found that the R-line TB of MgO:Cr^3+ or MgO:V^2+ comes from the first-order term of EPI. The elastic Raman scattering of acoustic phonons plays a dominant role in R-line TB of MgO:Cr^3+ or MgO:V^2+. 相似文献
999.
L. Maleki 《General Relativity and Gravitation》2008,40(5):895-905
Precision clocks and interferometers in space can test relativistic gravity with extremely high sensitivity. Yet, only a single
such test has been performed, namely the celebrated flight of a hydrogen maser in a sub-orbital trajectory in 1976 (GP-A mission).
This paper suggests some of the obstacles to space flight of precision instruments, and describes how the emergence of new
technology might offer a pathway for removing those obstacles. A brief review of emerging technologies is made, and new mission
concepts based on them are described. Some of the technologies that can impact more tests of relativistic gravity in space
at a more distant future are also described. 相似文献
1000.
This paper presents the planar Fiber Bragg Grating (FBG) hydrophone probe sensing principle, and theoretically and experimentally researches the probe structure sensitivity, the receiving sensitivity frequency response characteristic and the acceleration response property. Planar sheet is made of stainless steel, its thickness is 0.15 mm, its diameter is 15mm, and the length of hollow circular shell is 20 mm. For this size of the structure, the probe structure sensitivity is up to 23 fm/Pa, which is about 7300 times of the value of the bare fiber. The resonance frequency is 6.5 kHz, and the amplitude-frequency curve of the receiving sensitivity response is relatively flat within the frequency range of 100 Hz to 5.5 kHz. The output yielded by one unit acceleration (1m/s2) is equivalent to (2.52 to 3.26 Pa) acoustic pressure acting output. This probe structure is easy to form FBG hydrophone array by multiplexing technique. The research shows that this planar structure not only can form FBG hydrophone probe, but also can constitute optical FBG laser hydrophone probe. The structure can realize different bandwidth, different range acoustic pressure measurement by adjusting the geometrical size of the sheet. 相似文献