共查询到19条相似文献,搜索用时 859 毫秒
1.
本文通过偏振红外吸收光谱研究了铁电与反铁电液晶分子TFMHxPOCBC-D2(4-(trifluoromethylhexy-3-d2 carbonyl)phenyl 4′-octyloxybiphenyl caboxylate)在垂直排列取向液晶盒中CD2基团绕手征性烷基链转动的受阻行为.实验结果显示CD2的偏振红外吸收在Sm-C相不同于Sm-CA相.建立了一个CD2转动受阻模型,在这一模型的基础上,对CD2的偏振红外吸收进行了模拟计算,较好地解释了CD2红外吸收在铁电和反铁电液晶相下的行为差异,得到了CD2基团绕手征性烷基链转动受阻的结论.
关键词:
反铁电液晶
红外光谱
受阻转动 相似文献
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采用中频感应提拉法生长了高质量的Tm:Y2SiO5(Tm:YSO)晶体,测定了晶体的晶格常数和分凝系数.运用劳厄照相法确定了单斜晶系Tm:YSO晶体的三个偏振轴〈010〉,D1和D2,在室温下测量了三个偏振轴方向的吸收光谱、荧光光谱和荧光寿命,计算了晶体吸收峰的吸收线宽和吸收截面.研究发现,相对于其他两个偏振轴方向,D1方向在790nm处出现较强的吸收峰,
关键词:
2SiO5')" href="#">Tm:Y2SiO5
单斜晶系
吸收光谱
荧光光谱 相似文献
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研究了Yb:KLu(WO4)2晶体对非偏振抽运光的吸收以及连续波激光振荡性质. 晶体结构的低对称性导致晶体光谱呈强烈各向异性,最强的吸收和发射都发生在平行于Nm主轴的偏振方向上. Ng切向晶体具有最高的非偏振抽运光吸收效率和最大的激光功率产生潜力,2 mm长的晶体产生的最高连续波输出功率为11 W,相对于吸收抽运功率,光—光转换效率为68%,而斜率效率则达80%.
关键词:
吸收谱
发射谱
激光振荡
各向异性 相似文献
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确定具有各向异性、非线性吸收特性的调Q晶体内电偶极子的取向,是测量其吸收截面的重要条件。通过对Co2+:MgAl2O4晶体所属的空间群以及掺杂Co2+在晶胞结构中的位置对称性的分析,确定了晶体内电偶极子的跃迁方向主要是沿晶胞的4个体对角线方向分布的,建立了偏振入射光在Co2+:MgAl2O4晶体内传输的理论模型。实验测量了沿[100]方向切割的Co2+:MgAl2O4晶体在偏振入射光沿晶胞面对角线方向时的非线性透过率曲线,利用建立的模型对实验结果进行拟合,得到Co2+:MgAl2O4晶体在1.5μm波段的基态吸收截面和激发态吸收截面分别为(3.6±0.3)×10-19 cm2和(4.5±0.4)×10-20 cm2。 相似文献
7.
利用激光脉冲沉积(PLD)技术在(302)γ-LiAlO2衬底上成功生长了非极性的a面(1120)ZnO薄膜,光致发光谱(PL)带边发射峰半峰宽仅为115meV.研究了非极性ZnO薄膜光谱特性的面内各向异性,发现随着入射光偏振方向改变,在偏振透射光谱上,吸收边移动了20meV,这与A、B激子和C激子的能量差一致;而在拉曼光谱上,激发光偏振方向的改变导致E2模式的强度发生明显改变.
关键词:
非极性ZnO
2')" href="#">γ-LiAlO2
PLD 相似文献
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采用顶部籽晶提拉法,以K2W2O7为助溶剂,生长了Yb:KY(WO4)2新型激光晶体.经热重-差热分析,确定晶体熔点为1045℃,相变温度为1010℃.X射线粉末衍射测试,验证所生长的晶体为β-Yb:KY(WO4)2.晶体结构分析确定Yb:KY(WO4)2晶体由WO6八面体连接而成,WO6八面体是由双氧桥(WOOW)及单氧桥(WOW)构成.晶体粉末样品室温下的红外及拉曼光谱测试,确定WO6原子基团、双氧桥及单氧桥的振动频率.晶体的吸收峰位于940nm,980nm,发射峰位于989nm—1030nm.
关键词:
晶体结构
光谱
晶体生长 相似文献
11.
(CnH2n+1NH3)2 CdCl2Br2 compounds with n≥10 show several solid-solid phase transitions before descomposition takes place at 436 K. The results show a different behaviour between odd or even members of the series studied. The sequence of phase -- transitions can be interpreted as a dynamic order-disorder mechanism followed by a melting of the alkyl chains. 相似文献
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A new compound, K4(SO4)(HSO4)2(H3AsO4) was synthesized from water solution of KHSO4/K3H(SO4)2/H3AsO4. This compound crystallizes in the triclinic system with space group P1¯ and cell parameters: a=8.9076(2) Å, b=10.1258(2) Å, c=10.6785(3) Å; α=72.5250(14)°, β=66.3990(13)°, γ=65.5159(13)°, V=792.74(3) Å3, Z=2 and ρcal=2.466 g cm−3. The refinement of 3760 observed reflections (I>2σ(I)) leads to R1=0.0394 and wR2=0.0755. The structure is characterized by SO42−, HSO4− and H3AsO4 tetrahedra connected by hydrogen bridge to form two types of dimer (H(16)S(3)O4−?S(1)O42− and H(12)S(2)O4−?H3AsO4). These dimers are interconnected along the [1¯ 1 0] direction by the hydrogen bonds O(3)-H(3)?O(6). They are also linked by the hydrogen bridge assured by the hydrogen atoms H(2), H(3) and H(4) of the H3AsO4 group to build the chain S(1)O4?H3AsO4 which are parallel to the “a” direction. The potassium cations are coordinated by eight oxygen atoms with K-O distance ranging from 2.678(2) to 3.354(2) Å.Crystals of K4(SO4)(HSO4)2(H3AsO4) undergo one endothermic peak at 436 K. This transition detected by differential scanning calorimetry (DSC) is also analyzed by dielectric and conductivity measurements using the impedance spectroscopy techniques. The obtained results show that this transition is protonic by nature. 相似文献
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M.C. McCarthyP. Thaddeus 《Journal of Molecular Spectroscopy》2002,211(2):235-240
The microwave rotational spectra of the carbon-13 isotopic species of H2C3, H2C4, and H2C5 have been observed in a pulsed supersonic molecular beam by Fourier transform microwave spectroscopy. At high resolution all of the rotational lines exhibit hyperfine structure produced by the magnetic interaction between the nuclear spin of 13C and the overall rotation of the molecule. The component of the nuclear spin-rotation tensor along the a-inertial axis is large for most isotopic species, especially at the carbene carbon; at this position Caa is two to three times larger than at other substituted positions along the chain. In contrast to both H2C3 and H2C3, in H2C4Caa exhibits a pronounced alternation along the carbon chain backbone. Following detection of the five carbon-13 isotopic species and D2C5, an experimental structure (r0) has been determined to high accuracy for H2C5. 相似文献
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Amorphous TiO2 thin films and ZnFe2O4 doped TiO2 composite films were deposited by radio frequency magnetron sputtering. The effect of ZnFe2O4 doping on the optical properties of TiO2 thin films was reported. Our results show that the absorption edge of TiO2 thin films and composite films exhibits a blue shift with decreasing annealing temperature. The absorption edge of composite films has moved to visible spectrum range, and a very large red shift occurs in comparison with TiO2 thin film. An enhanced photoluminescence in ZnFe2O4 doped anatase TiO2 thin film at room temperature. 相似文献
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用射频/直流磁控溅射法制备了CeO2/Nb2O5双层氧敏薄膜,利用X射线光电子能谱(XPS),描述并解释了单层CeO2薄膜中氧随温度变化的动力学行为,以及CeO2/Nb2O5薄膜界面对氧敏特性的影响.通过对Ce3d XPS谱的高斯拟合,计算了Ce3+浓度并给出了判定Ce4+还原的标志.结果表明,界面效应可以提高CeO2/Nb2O5薄膜中Ce4+的还原能力,使之远远高于单层CeO2薄膜,这对薄膜的氧敏特性是极为有利的.
关键词: 相似文献
16.
A. Devendar Reddy S.G. Sathyanarayan G. Sivarama Sastry 《Solid State Communications》1982,43(12):937-940
D.C. electrical conductivity, DTA and coulometric studies on (NH4)3 H(SO4)2 single crystals are made. Conductivity is markedly anisotropic with maximum along c1 direction. A sudden jump in the conductivity plot along c1 direction at 413 K is supported by a large endothermic peak in DTA, confirming the presence of transition at this temperature. The values of activation energy calculated from conductivity measurements indicated that the charge carriers are protons. This was further confirmed by coulometric experiment where the gas evolved was hydrogen, as established by a gas chromatograph and the volume of H2 released agreed with that expected from electrolysis. The mechanism of protonic conduction in this crystal is discussed. 相似文献
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This paper describes the synthesis and characterization of self-assembled organic-inorganic layered perovskite compounds, (C6H5-CnH2n-NH3)2PbBr4 (n=1-4). the effect of the number of carbon atoms of the alkyl chain length (n) on optical properties has been studied. (C6H5-CnH2n-NH3)2PbBr4 films fabricated by spin-coating are microcrystalline form, single phase and oriented with the c-axis. Crystallinity, the maximum PL intensity and the lifetime of exciton emissions varied with the number of carbon atoms. the lowest-energy exciton splits into a few fine-structure levels at low temperatures. Time-resolved photoluminescence spectra reveal that (C6H5-CnH2n-NH3)2PbBr4 shows both singlet and triplet excitons. with decreasing temperature, triplet exciton emissions become dominant for (C6H5-CnH2n-NH3)2PbBr4 (n=1-3), while (C6H5-C4H8-NH3)2PbBr4 shows mainly singlet exciton emissions. The intersystem crossing from excited singlet state to triplet state plays an important role in the relaxation process of excitons. 相似文献
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The chemical preparation, the calorimetric studies and the crystal structure are given for two new organic sulfates NH3(CH2)5NH3SO4 1.5H2O (DAP-S) and NH3(CH2)9NH3SO4·H2O (DAN-S). DAP-S is monoclinic P21/n with unit cell dimensions: a=11.9330(2) Å; b=10.9290(2) Å; c=17.5260(2) Å; β=101.873(1)°; V=2236.77(6) Å3; and Z=8. Its atomic arrangement is described as inorganic layers of units and water molecules separated by organic chains. DAN-S is monoclinic P21/c with unit cell parameters: a=5.768(2) Å; b=25.890(10) Å; c=11.177(5) Å; β=115.70(4)°; V=1504.0(11) Å3 and Z=4. Its structure exhibits infinite chains, parallel to the [100] direction where the organic cations are interconnected. In both structures a network of strong and weak hydrogen bonds connects the different components in the building of the crystal. 相似文献