Journal of research of the National Bureau of Standards. Section A, Physics and chemistry最新文献

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Reduction of Space Groups to Subgroups by Homogeneous Strain. 通过同质应变将空间群还原为子群。

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry

Pub Date : 1963-09-01 Epub Date: 1963-10-01 DOI: 10.6028/jres.067A.042

H S Peiser, J B Wachtman, R W Dickson

It is assumed that the symmetry elements possessed by a strained crystal will be those common to the unstrained crystal and to the macroscopic state of strain. This principle has been applied to show all of the possible subgroups to which a given space group can be lowered by homogeneous strain for all of the 230 crystallographic space groups.

假定受应变晶体所具有的对称元素是未受应变晶体和宏观应变状态所共有的对称元素。应用这一原理，可以显示出在所有 230 个晶体学空间群中，特定空间群通过均匀应变可以降低到的所有可能子群。

引用次数: 0

Resolution Limits of Analyzers and Oscillatory Systems 分析仪和振荡系统的分辨率极限

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry

Pub Date : 1963-09-01 DOI: 10.6028/jres.067A.048

E. Corliss

This paper considers the resolution limits of those analyzers and oscillatory systems whose performance may be represented by a second-order differential equation. The “signal uncertainty” product Δf·Δt is shown to be controlled by the ability of a system to indicate changes in energy content. The discussion refers the functioning of the system to a signal space whose coordinates are energy, frequency, and time. In this signal space, the product of the resolution limits, U = (ΔE/E0) (Δf/f0) (Δt/T0) is the volume of a region within which no change of state in the system may be observed. Whereas the area element Δf·Δt is freely deformable, no operations upon either Δf or Δt can further the reduction of the energy resolution limit. Thus U is irreducibly fixed by the limiting value of ΔE/E0. By considering the effects of noise upon ΔE/E0, and thus upon U, the paper demonstrates the rise of statistical features as signal-to-noise ratios decrease. Functional relationships derived from ΔE/E0 and U are tabulated. These equations facilitate computation of the limits of observable changes of state in a system, and they provide guidance for the design of experiments to apportion the uncertainties of measurement of transient phenomena as advantageously as possible. A reference bibliography and appendices giving somewhat detailed proofs are included.

本文考虑了性能可以用二阶微分方程表示的分析仪和振荡系统的分辨率极限。“信号不确定度”产品Δf·Δt显示由系统指示能量含量变化的能力控制。讨论将系统的功能描述为一个以能量、频率和时间为坐标的信号空间。在这个信号空间中，分辨率极限U = (ΔE/E0) (Δf/f0) (Δt/T0)的乘积是一个区域的体积，在这个区域内，系统中没有状态变化可以被观察到。而面积元Δf·Δt是可自由变形的，对Δf或Δt的任何操作都不能进一步降低能量分辨率极限。因此U被ΔE/E0的极限值不可约地固定。通过考虑噪声对ΔE/E0的影响，从而对U的影响，本文证明了随着信噪比的降低，统计特征的增加。由ΔE/E0和U导出的函数关系表。这些方程有助于计算系统中可观察到的状态变化的极限，并为实验设计提供指导，以尽可能有利地分配瞬态现象测量的不确定性。参考书目和附录给出了一些详细的证明。

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引用次数: 6

Melting Temperature and Change of Lamellar Thickness with Time for Bulk Polyethylene. 块状聚乙烯的熔化温度和层状厚度随时间的变化。

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry

Pub Date : 1963-09-01 Epub Date: 1963-10-01 DOI: 10.6028/jres.067A.046

James J Weeks

The melting temperature of linear polyethylene has been obtained as a function of the time and temperature of crystallization. Recrystallization was minimized by a special melting procedure. By interpreting the melting points as characteristic of a given lamellar thickness, it was found that the thickness of crystals of appreciable age increased linearly with the logarithm of their time of existence. The lowest melting (i.e., thinnest) lamellae in a given specimen may be assumed to have either existed for only a short period of time, or to have been impeded in their growth in the chain direction, and they were found to have an estimated thickness close to that predicted by recent kinetic theories of polymer crystal growth with chain folding.

线性聚乙烯的熔化温度是结晶时间和温度的函数。通过特殊的熔化程序将再结晶降至最低。通过将熔点解释为给定薄片厚度的特征，可以发现具有相当年限的晶体厚度随其存在时间的对数呈线性增长。可以认为，特定试样中熔点最低（即最薄）的薄片要么只存在了很短的时间，要么在链方向上的生长受到了阻碍，并且发现它们的估计厚度接近于最近的聚合物晶体生长与链折叠动力学理论所预测的厚度。

引用次数: 0

Preparation of Anhydrous Single Crystals of Rare-Earth Halides 稀土卤化物无水单晶的制备

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry

Pub Date : 1963-07-01 DOI: 10.6028/jres.067A.036

N. H. Kiess

Anhydrous rare-earth halides are prepared by the conversion of the rare-earth oxide to the halide by means of its reaction with the appropriate ammonium halide. Without transfer from the reaction vessel, the halide is melted, then crystallized by slow cooling. The resulting solid usually contains single crystals large enough to permit spectroscopic studies of the compounds.

无水稀土卤化物是由稀土氧化物与适当的卤化铵反应转化为卤化物而制备的。没有从反应容器转移，卤化物被熔化，然后通过缓慢冷却结晶。所得的固体通常含有足够大的单晶，可以对化合物进行光谱研究。

引用次数: 8

Relaxation Modes for Trapped Crystal Point Defects 俘获晶点缺陷的弛豫模式

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry

Pub Date : 1963-07-01 DOI: 10.6028/jres.067A.030

A. Franklin

Group representation theory is applied to the problem of calculating the relaxation modes of a point defect trapped near an impurity atom or other defect in a crystal, where more than one set of neighboring sites is available to the point defect. For illustration, the case of a cation vacancy trapped near a divalent impurity in the sodium chloride lattice is treated, including nearest- and next-nearest-neighbor sites.

将群表示理论应用于计算被困在杂质原子或晶体中其他缺陷附近的点缺陷的弛豫模式的问题，其中点缺陷有多个相邻的位点可用。为了说明，在氯化钠晶格中，阳离子空位被捕获在二价杂质附近的情况被处理，包括最近邻和次近邻的位置。

引用次数: 16

A Note on the Galvanomagnetic and Thermoelectric Coefficients of Tetragonal Crystalline Materials 关于四方晶体材料的磁、热电系数的注记

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry

Pub Date : 1963-07-01 DOI: 10.6028/jres.067A.031

W. C. Hernandez, A. Kahn

The independent Hall, magnetoresistive, and thermoelectric coefficients for a tetragonal crystal have been tabulated and geometric configurations for their experimental measurement have been determined. These coefficients have been calculated on assumptions of several simple ellipsoidal models, in the range of nondegenerate statistics. Implications of experimentally observed isotropy or anisotropy of transport properties on the structure of the energy surfaces are noted.

独立的霍尔系数，磁阻系数和热电系数的四角形晶体已被制表，并确定了几何构型的实验测量。这些系数是在几种简单椭球模型的假设下，在非退化统计的范围内计算出来的。注意到实验观察到的输运性质的各向同性或各向异性对能量表面结构的影响。

引用次数: 2

Symmetry Splitting of Equivalent Sites in Oxide Crystals and Related Mechanical Effects 氧化物晶体中等效位的对称分裂及相关力学效应

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry

Pub Date : 1963-07-01 DOI: 10.6028/jres.067A.029

J. B. Wachtman, H. Peiser, E. Levine

Changes in the symmetry of a crystal caused by an applied strain have been used to show in what circumstances an internal friction peak can result from the motion of isolated point defects. General rules are given to make the prediction, and these are applied to several structures of common oxides. The prediction for rutile is compared with experimental results which are interpreted by the movement of titanium ions between interstitial positions in the structure.

由外加应变引起的晶体对称性的变化已被用来说明在什么情况下孤立点缺陷的运动可以产生内摩擦峰。给出了预测的一般规则，并将这些规则应用于几种常见氧化物的结构。对金红石的预测结果与实验结果进行了比较，并用钛离子在结构间隙位置之间的运动来解释。

引用次数: 15

Photolytic Behavior of Silver Iodide1 碘化银的光解行为

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry

Pub Date : 1963-07-01 DOI: 10.6028/jres.067A.032

G. Burley

Silver iodide exposed to high intensity radiation in the visible light spectrum was found to yield a powder X-ray diffraction pattern showing marked deviations from ideality. It was found possible to correlate these with a decrease in primary extinction, indicating a constant progress from an ideal to a mosaic type crystallinity. Large single crystals showed pronounced asterism in transmission Laue photographs under similar experimental conditions. Small amounts of colloidal silver were detected. A mechanism for this process in silver iodide is proposed, in general agreement with the theory of the photographic process. The primary difference from the other silver halides appears to be a considerably slower rate, permitting the observation of a two step process in detail.

碘化银暴露在可见光谱的高强度辐射下，发现产生粉末x射线衍射图样，显示出明显偏离理想。人们发现这些可能与原始灭绝的减少有关，表明从理想结晶到镶嵌型结晶的不断进展。在相似的实验条件下，大单晶在透射劳厄照片中显示出明显的星形。检测到少量胶体银。在碘化银中提出了这一过程的机理，与照相过程的理论基本一致。与其他卤化银的主要区别似乎是相当慢的速率，允许详细观察两步过程。

引用次数: 10

A Phase Study of the System: Oxalic Acid/Acetic Acid/Water; Its Significance in Oxalic Acid Crystal Growth1 草酸/乙酸/水体系的物相研究其在草酸晶体生长中的意义

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry

Pub Date : 1963-07-01 DOI: 10.6028/jres.067A.037

J. Strassburger, John L. Torgesen

The presence of limited amounts of water appears to improve the quality of anhydrous oxalic acid single crystals grown from acetic acid solutions. Water concentrations in the saturated solutions which allow crystallization of the anhydrous acid have been determined from the phase study of this ternary system. Near 50 °C the anhydrous acid crystallizes from solutions containing up to 5.2 weight percent water, while the dihydrate appears when water is in excess of this amount. The phase diagram shows a minimum content of oxalic acid in solution at a solvent composition near 83 percent acetic acid, 17 percent water. The solubility increases with increased acetic acid to the isothermal invariant point, found experimentally at a measured temperature of 50.21 °C to have the composition 20.94 percent oxalic acid, 73.89 percent acetic acid, 5.17 percent water. Decreasing solubility occurs at higher acetic acid concentrations. The maximum water content which allows crystallization of anhydrous acid increases with increasing crystallization temperature. The solubility of oxalic acid in acetic acid/water mixtures at 40° and 50 °C is reported.

适量的水的存在似乎可以改善从醋酸溶液中生长的无水草酸单晶的质量。在允许无水酸结晶的饱和溶液中，水的浓度已由三元体系的相研究确定。在50°C附近，无水酸从含有高达5.2%重量的水的溶液中结晶，而当水超过这个量时，就会出现二水合物。相图显示了在溶剂组成接近83%醋酸，17%水时，溶液中草酸的最低含量。溶解度随着乙酸的增加而增加到等温不变点，实验发现在50.21℃的测量温度下，草酸的组成为20.94%，乙酸为73.89%，水为5.17%。醋酸浓度越高，溶解度越低。允许无水酸结晶的最大含水量随着结晶温度的升高而增加。报道了草酸在40°和50°C的醋酸/水混合物中的溶解度。

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引用次数: 5

Wavelength Calibrations in the Far Infrared (30 to 1000 Microns) 远红外线波长校正(30至1000微米)

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry

Pub Date : 1963-07-01 DOI: 10.6028/jres.067A.038

K. Rao, R. V. de Vore, E. K. Plyler

A discussion is presented of certain calibration procedures employed in the region 30 to 1000 microns. Calculated positions for the pure rotational absorption lines of the CO, HCN, and N2O molecules are given, and a map of the pure rotational absorption lines of the H2O molecule as recorded with a Perkin-Elmer model 301 spectrophotometer is shown.

讨论了在30至1000微米范围内采用的某些校准程序。给出了CO、HCN和N2O分子的纯旋转吸收谱线的计算位置，并给出了用珀金-埃尔默301型分光光度计记录的H2O分子的纯旋转吸收谱线图。

引用次数: 44

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