共查询到18条相似文献,搜索用时 875 毫秒
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在这篇论文里我们证明,与某些作者所了解的不同,我们的流体的容变粘滞弹性理论不仅仅是在结构弛豫的情况中有效,而是对所有三种弛豫——热弛豫、结构弛豫与化学弛豫——都是同样有效的。从我们的容变不可逆性方程可以推到Herzfeld与Rice原为热弛豫所假定的热不可逆性方程。又可以证明的是在化学弛豫的情况中我们的容变不可逆性方程也包含着Liebermann由分子运动理论考究所得到的化学不可逆性方程。关于这理论在声吸收及速变现象中的应用,我们证明利用适当的热力学考究便可以从我们的压缩性理论所给的结果直接推到在热弛豫情况下有效的Bourgin-Kneser方程及在化学弛豫情况下可以有效的Liebermann方程。这个推导并揭发出来Liebermann的声吸收方程仅对液体说可以是一个良好的近似。我们附带地指出,在气体的情况中,某些已发表的声吸收及速变的实量结果的准确度已可以使我们从这些结果来算定气体的静态与立刻两压缩系数β0及β∞,从而确定热容量的两比值γ0及γ∞与外态内态两热容量C(e)及C(i)。这样我们又能从这些结果取得一些有关分子构造及分子碰撞过程中能量转移的结论。最后,我们讨论了我们的容变粘滞系数的定义的适当性。 相似文献
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根据对聚酰胺类高聚物红外光谱的类比和对聚酰胺6试样进行氘化和碘处理后红外光谱的改变,以及根据对拉伸过的聚酰胺6薄膜试样的偏振红外光谱的观察,我们对聚酰胺6红外光谱中400cm-1—1400cm-1之间的主要吸收带,作了如下解释:1370cm-1吸收带为ν(cщN);1265cm-1和1205cm-1吸收带为δN-H+ν(cщN)(酰胺Ⅲ);1170cm-1吸收带为ν(cN);730cm-1吸收带为γ(CH2)[当(CH2)n的n≥4时];690cm-1吸收带为δN-H(面外);580cm-1吸收带亦为δN-H(面外)。 相似文献
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研究了Er1.0P5O14铒非晶玻璃的红外量子剪裁现象. 从吸收谱和激发光谱的计算比较中肯定了Er1.0P5O14非晶 玻璃的1537.0 nm红外荧光为多光子量子剪裁荧光. 从Er1.0P5O14非晶玻璃的可见和红外荧光发射光谱中发现激发2H11/2, 4G11/2和4G9/2能级所导致的4I13/2→4I15/2量子剪裁红外荧光很强;基于自发辐射速率、无辐射弛豫速率和能量传递速率等参数的计算,对其量子剪裁机理进行了分析.发现起源于基态的强下转换能量传递{2H11/2→4I9/2,4I15/2→4I13/2},{4G11/2→4I13/2, 4I15/2→2H11/2},{4G9/2→4F7/2,4I15/2→4I13/2}和{4G9/2→4I13/2, 4I15/2→2H11/2}是导致Er1.0P5O14非晶玻璃具有强的三光子和四光子量子剪裁红外荧光的原因.研究结果对改善太阳能电池效率有一定意义. 相似文献
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采用分布反馈式半导体激光器作为探测光源,结合程长为100 m的离散型多通吸收池,采用直接吸收光谱技术,对室温下中心波长2.33 μm附近各种低体积分数的CO及混合气体(CO,CHCH4和N2)的直接吸收光谱进行了测量。选择CO在4 288.289 8 cm-1位置的吸收谱线和CH4在4 287.650 15 cm-1处的吸收谱线进行痕量探测,在40 698 Pa的总压力下,实验测得CO的探测极限为8.15×10-6(信噪比约为216),CH4的探测极限为18.48×10-6(信噪比约为147)。 相似文献
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研究了以Co2+:MgAl2O4晶体为饱和吸收体的LD抽运Er3+,Yb3+共掺磷酸盐玻璃激光器.针对双掺离子之间的能量传递和Er3+的多种跃迁过程,结合Co2+:MgAl2O4晶体中Co2+离子的饱和吸收特性,给出了详尽的速率方程,在其基础上进行了数值分析,分析了输出镜透过率、激光介质长度、谐振腔长度、腔内往返损耗、饱和吸收体长度对激光阈值、峰值功率、单脉冲能量以及脉冲宽度的影响. 相似文献
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LiFePO4在含Li+水溶液中的电化学性能稳定性与水溶液的pH值密切相关,当溶液的pH值达到11后LiFePO4在充放电循环过程中的容量衰减十分明显. 通过循环伏安测试、交流阻抗测试、电极充放电性能测试、非原位X射线衍射测试以及化学分析的方式对其容量衰减机理进行了研究. 结果表明LiFePO4在pH=7的LiNO3水溶液中具有相对最高的电化学稳定性,但是LiFePO4材料在水溶液中较之其在有机电解液中依然会有较差的电化学性能表现. 认为LiFePO4在水介质中的容量衰减现象归因于其在持续充放电过程中的Li、Fe、P溶解,同时电极表面也会附着一层沉淀物. 这些最终导致了材料晶体结构的破坏、电极极化的增大以及电极容量的衰减. 相似文献
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本文采用共烧结工艺将纳米Ag颗粒引入Yb3+, Er3+共掺的NaYF4上转换材料中, 利用X射线衍射及扫描电子显微镜技术对制备的NaYF4材料进行结构特性和表面形貌的表征, 通过吸收谱及荧光光谱测试技术对NaYF4材料光吸收及光发射特性进行表征. 通过对纳米Ag颗粒引入量的优化, 获得了Yb3+, Er3+共掺的NaYF4上转换材料荧光发射峰的增强, 300—800 nm全光谱范围内增益达28%, 在544 nm处获得最大增益55%, 具有显著的荧光增强效果. 同时分析了不同数量纳米Ag颗粒的引入对NaYF4材料吸收谱及光致发光特性影响, 指出了表面等离子激元的光猝灭及共振吸收增强作用机理. 相似文献
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J. Murín 《Czechoslovak Journal of Physics》1986,36(6):740-750
The paper deals with a study of the proton nuclear magnetic resonance (NMR) of crystallization water in isomorphous monohydrates MgSO4. 1 H2O and FeSO4. 1 H2O in the temperature range 123–313 K. The NMR second moment for diamagnetic MgSO4. 1 H2O shows only a weak dependence on temperature but the one for paramagnetic FeSO4. 1 H2O is rather strong. Results obtained for FeSO4. 1 H2O are in a good agreement with the Kroon's theory of NMR in paramagnetics. The Curie-Weiss constant and the effective magnetic moment of Fe2+ ions in FeSO4. 1 H2O are derived from the temperature dependence of NMR second moment. The motion of molecules of crystallization water in these hydrates is discussed on the basis of temperature dependences of the width and second moment of NMR spectra. 相似文献
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《Radiation measurements》2000,32(2):123-128
MgSO4:Dy, MgSO4:Tm and MgSO4:Dy,Mn thermoluminescence (TL) phosphors have been prepared and their emission spectra were measured using a linear heater and optical multichannel analyzer. Emission bands at about 480, 580 and 660 nm of MgSO4 doped with Dy were observed in three dimension (3D) glow curve. Emission bands about 360, 460, and 660 nm were observed in a 3D glow curve of MgSO4 doped with Tm. The emission spectra of MgSO4:Dy and MgSO4:Tm are attributed to the characteristic emission wavelengths from transitions of Dy3+ and Tm3+ respectively. The results show that the structures of traps in matrix materials determine the activation energy distribution and dopant energy levels of rare earth ions are related with the emission spectrum wavelengths of sulfate phosphors. The intensities of the glow peaks in both bands at about 480 and 580 nm in MgSO4 doped Dy and Mn were dramatically reduced in comparison with that of MgSO4 doped Dy except above 300°C. It means that the trapping structures of MgSO4 :Dy phosphor has greatly been altered by the co-dopant Mn but no change is observed in wavelengths of the emission spectra. 相似文献
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QUANTUM EFFICIENCY AND MULTIPHONON NONRADIATIVE TRANSITION OF Er3+ IONS IN FLUORIDE GLASS 总被引:1,自引:0,他引:1 下载免费PDF全文
Optical absorption, emission and excitation spectra, lifetimes of 4S3/2 state and 4F9/2 state from 10K to 500K, and Raman spectra were measured for Er3+ ions in fluoride glass. The radiative transition probabilities were calculated on the basis of Judd-Ofelt theory. The nonradiative transition probabilities and the quantum efficiencies were determined by calculating the difference between the measured lifetimes and the calculated radiative transition probabilities. The temperature dependence of nonradiative transition provavility was investigated using the Huang-Rhys theory of multiphonon relaxation , in which two kinds of phonons as well as the parameter s were taken into consideration. A fairly good agreement of the theoretical calculation with the experimental results has been obtained. The value of s is estimated and the effect of s is discussed. 相似文献
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J.-F. Dufrêche M. Duvail B. Siboulet M. Jardat O. Bernard 《Molecular physics》2014,112(9-10):1405-1417
We study mutual diffusion of associated electrolyte in water. A theory based on the Smoluchowski equation and on the mean spherical approximation is proposed. It is found to be valid up to molar concentrations. The values of the association constant obtained for ZnSO4 and MgSO4 aqueous solutions are consistent with further methods of measurements. Thanks to the elimination of fast variables method, the theory can be generalised to any association in solution. Comparison with molecular dynamics and Brownian dynamics simulations in the case of MgSO4 indicates that the pair is a global association phenomenon since it corresponds to several association phenomena (contact ion pair and solvent separated ion pair). 相似文献
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J.H. Huang X.H. Gong Y.J. Chen Y.F. Lin J.S. Liao X.Y. Chen Z.D. Luo Y.D. Huang 《Applied physics. B, Lasers and optics》2007,89(1):73-80
Polarized spectral properties of Er3+:NaGd(WO4)2 single crystal are reported. The crystal was grown by the Czochralski method. The Judd–Ofelt theory was applied to analyze
the polarized absorption spectra and then calculate the spontaneous emission probabilities, radiative lifetimes, and branching
ratios. Fluorescence decay curves of the 4
I
13/2, 4
I
11/2, and 4
S
3/2 multiplets for the Er3+ ions were measured. Stimulated emission cross-sections of the 4
I
13/2→4
I
15/2 transition obtained by the Fuchtbauer–Ladenberg formula and the reciprocity method were compared. Multi-phonon relaxation
rates of the crystal were estimated. Green up-conversion fluorescence around 531 and 552 nm was observed, and the possible
up-conversion mechanisms were proposed.
PACS 78.20.-e; 42.70.Hj 相似文献
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M. Schneider F. Hase G.C. Toon 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(3):465-474
We use high quality ground-based solar absorption spectra measured in close coincidence with Vaisala RS92 radiosonde in situ water vapor profiles to demonstrate that a Voigt line shape model yields systematic errors in the remotely sensed tropospheric water vapor profiles. We analyse absorption signatures of 4 H216O and 2 HD16O bands situated between 790 and 4710 cm−1. We find that applying a speed-dependent Voigt line shape model instead of a Voigt line shape model significantly improves the agreement between the water vapor profiles obtained by the radiosondes and by infrared remote-sensing in the different bands. An optimal agreement is obtained for a Γ2 (relaxation rate for speed-dependence) of 6-21% of Γ0 (Voigt relaxation rate), which is consistent to the values derived from laboratory experiments. Our study suggests that further extensive laboratory investigations of line shape models are a key for improving the quality of modern water vapor remote sensing products. 相似文献