The effect of zinc ions on the fluorescence spectra of (La, Zn)OF:Sm powder phosphors

This paper reports the fluorescence properties of a new series of (La, Zn) OF:Sm³⁺ powder phosphors. The measured fluorescence spectra were analyzed by computing the color coordinates and relative fluorescence intensity ratios (ED/MD). A bright yellowish-orange color was observed from these powder phosphors under a UV-source due to the confirmation of the transitions ⁴G_5/2→⁶H_5/2, ⁴G_5/2→⁶H_7/2, and ⁴G_5/2→⁶H_9/2. Scanning electron microscopic studies were performed to understand the average grain size of the synthesized powder phosphors.     

人类对超声的听觉感知及应用前景

本文对人类通过骨传导所产生的超声听觉感知，就以下四方面进行介绍：１．感知的方法、频率和强度范围；２．感知机理；３．可能的应用；４．值得研究的问题。     

巯基棉分离富集原子吸收光谱法测定铜精矿中金银

本文详细地研究了在ＨＣｌ介质中,巯基棉分离富集Ａｕ,Ａｇ,ＫＩＯ３－ＨＣｌ解脱Ａｕ,原子吸收分光光度法测定金、银的方法。本方法一次溶样连续测定Ａｕ,Ａｇ,简便快速,分析结果可靠,在Ａｕ３２μｇ,Ａｇ４００μｇ范围内,Ａｕ回收率９８．８％－１０１．２％,ＲＳＤ为３％,Ａｇ回收率９７．３％￣１０１．３％,ＲＳＤ为２％。     

不同溶剂中取代基对芳香胺红外吸收光谱的影响

对２１种芳香胺在不同极性的溶剂中测定了红外光谱,并对不同取代基对氨基的对称伸缩动和非对称伸缩振动吸收峰峰位的影响进行了讨论。甲基在不同极性的溶剂中表现不同的电子效应;甲氧基处于氨基的邻位的电子效应和处于间位时不同,氯和硝基取代基使氨基的两吸收峰均向蓝移,氨基取代基使氨基的两吸收峰向红移。     

高温高压下纳米金刚石粉的特性研究

 研究了炸药爆轰合成的纳米金刚石粉在高温（约1 600 K）、高压（5.2 GPa）条件下的行为。将纳米金刚石粉与粉末合金（Ni₇₀Mn₂₅Co₅、100^#）混合、压制成圆片,与合金片 （Ni₇₀Mn₂₅Co₅）和人造石墨片一起交替放入高温高压合成腔体内,进行高温高压实验。实验结果表明：在高温高压条件下,纳米金刚石粉不能长大,反而石墨化了;在相同的高压和保温时间条件下,随着温度的降低,纳米金刚石粉的石墨化程度减弱,纳米金刚石粉的纳米颗粒长大,可长成0.1 mm尺寸的金刚石颗粒（温度为1 070 K左右）。而在此条件下,人造石墨不能合成金刚石,一般金刚石晶体要变成石墨相。这进一步表明,纳米金刚石颗粒表面的活性使得它可以在较低的温度下长成较大颗粒的金刚石。     

氮烃混合工质中氖的作用机理

氮烃混合工质由于有较大的制冷量,在节流制冷器中已广泛应用,然而它的制冷温度却较高,在使用中受到一定的限制。文中通过对在氮烃混合工质中加入氖的分析,揭示了氖降低混合工质制冷温度的机理     

一种新型的单色高亮度LED物屏

本介绍一种新型的单色LED物屏。该物屏具有成像清晰、造价低廉、制作方便的特点。     

中心力场中散射角的简洁推导

本文从牛顿方程及角动量守恒定律出发 ,利用矢量函数的微积分运算技巧简捷地推导出中心力场中散射角 φ,避免了经典教科书中从轨道方程出发推导出 φ的繁琐性 ,不仅计算简洁 ,而且物理过程明确 .     

The A = 51 mirror nuclei 51Fe and 51Mn

Eighteen previously unknown γ-ray transitions were identified in the T _z = - 1/2 nucleus ⁵¹Fe following the fusion-evaporation reaction ³²S(²⁸Si,2α1n)⁵¹Fe. The level scheme reaches the fully aligned I ^π = 27/2^- terminating state of the five holes in the f _7/2 shell. The 17/2^- state was found to be isomeric, and the lifetime was measured to be 2.87 ns. The mirror symmetry of ⁵¹Fe and ⁵¹Mn is discussed, and the level scheme of ⁵¹Fe is compared to shell-model calculations. Received: 20 July 2000 / Accepted: 1 August 2000     

Confined electron and shallow donor states in graded GaAs/Al Ga As spherical quantum dots

A theoretical study is performed on the confined electron and shallow donor states properties in graded GaAs/Al_xGa_1-xAs spherical quantum dots. The two lowest energy levels of a confined electron are obtained taking into account the dependence of the electron effective mass on the spatial profile of the Al molar fraction. The ground state of a single Si shallow donor, which may be located at an arbitrary position in the structure, is calculated through a variational approach. Depending on the dot interface width and localization, we find that the energy levels of the electron and donor states for the system under study can be blue or red shifted appreciably in comparison to those calculated within the sharp interface picture. We show that it is necessary to have accurate information concerning the interface of semiconductor dots whose samples are used in the experiments, in order to achieve a better understanding of their optical properties. Received 31 May 1999