水的热膨胀的特点演示的探讨

初中物理:“水的热膨胀的特点”的演示在我数年的教学中一直没有做过,这主要是因为:当堂演示太费时间又和讲课配合不好,如让学生等着看实验结果,则大部同学感到索然无味,如不等结果而先讲其他内容,则又打乱了课堂的系统性。加以有些学校根本没有水的最大密度演示器,因之过去讲这一节时,往往只用挂图一讲了事。但后来在物理通报上看到一些老师对这个演示采取了各种不同的方法,从而取得了较好的成绩。为了提高教学质量,我把通报上前后所介绍的几种方法都做了几遍,从不断变换着的操作中给了我新的启示,我又用了     

核物质的物态方程的研究

在相对论σ–ω模型的单圈图近似下,详细推导了核物质的能量密度和压强密度表达式,数值计算了核物质的结合能和压强随核密度的变化,并分别在热力学和流体力学的理论框架下,计算了核物质的压强密度,结果表明这两种方法得到的压强密度相同.     

氧的超导性的发现

氧是生物体和生命过程中的一种重要化学元素,也是大气的重要组成部分．氧的化学式为Ｏ２．从较早的科学研究中已经知道［１］,氧具有很强的顺磁性,随着温度的降低,不但氧的顺磁性增强,而且在一定的低温度下会从气态氧转变为液态氧,在一定的低温和压力条件下,还会从...     

气体的压强跟体积的关系的演示

初中物理学上册第三章第35节大气压的一个实验是:水由喷嘴向压强较低的玻璃管中喷入(见原书图55)。这个实验如果没有抽气机,就很难做。我     

铝的激发光谱的测量

用１２０ｋｅＶ的Ａｌ＋离子与１０μｇ／ｃｍ２的碳箔相互作用，研究ＡｌⅠ、ＡｌⅡ和ＡｌⅢ的激发光谱，其结果与其它实验进行了比较。     

光的干涉的应用

在科学和技术領域中,人們不断地利用着光的干涉原理解决了許多复杂的实际問題。例如在技术中对于光学表面磨光的检驗,光学部件质量的精密检定,长度微小改变的精密測定(干涉膨胀仪),增透光薄膜的制作,干涉滤光片的制作,軸承滾珠的分类和检驗等等。此外,对于光譜譜线精細結构的研究,物貭折射率的精密测定等也都逐渐轉入利用光的干涉方法来进行。由于光的干涉的应用是如此之广,因而对光干涉应用的各个方面作一全盘介紹显然是很难作到的,故仅就几个重要应用方面作一初步介紹。一、利用光的干涉检定螺旋測微器(千分尺) 在測微器的待量度的平面之間夹入一已知其厚度     

稳定的驻极体的制备

本文以实验资料和新近理论为依据,论述了稳定的驻极体的制备。在常温下工作的驻极体最好用聚四氟乙烯(PTFE)或聚全氟乙丙烯(FEP)制作;而长期在高温环境中(80—90℃)工作的驻极体,最好用聚二氯对苯撑二甲基(PDCPX)制作。稳定的驻极体的制备,不管用什么方法,极化后的热处理对其稳定性是必要的。     

气体的压强与体积的关系的实验设计

气体的压强与体积的关系的实验设计陈银潭（江苏兴化市合塔中学２２５７４２）实验目的探索气体的压强与体积的关系．方法一实验器材５０ｍｌ玻璃注射器一只，彩色橡皮膜一块（或小气球）．器材装置（图１）图１实验步骤ｈ用橡皮膜做成直径约Ｚｅｍ的小气球，扎紧口后放人...     

水的表面张力的演示

1.仪器装置取直径为0.5毫米的铜丝做成一个直径为8厘米的圆环,环的直径两端接两根铜丝,铜丝的另一端拧在一起插入软木塞里。再取一只底部尖一点的试管,并且准备一些沙粒和一只盛水缸。 2.操作首先在试管里放些沙粒,用带有     

光的衍射的应用

光波也正如其他类型的波动(例如声波)一样,在其自由传播过程中,当受到某种形式的障碍物的阻挡或限制,都将产生与自由传播方向相偏离的传播現象。这种現象通常借呈现出的一套明暗相间的花样而被我們发觉到。这种現象通常被称作“衍射”。     

Superlinear photoluminescence in silicon nanocrystals: The role of excitation wavelength

We study the influence of the wavelength of picosecond excitation pulses on the properties of photoluminescence (PL) in a series of samples of silicon nanocrystals prepared by ion implantation into silica matrix. We observed a gradual change in the behaviour of the PL fast component (spectral shape, decay times, pump-intensity dependence) when tuning the excitation wavelength from 355 to 532 nm. We interpret the results in terms of an interplay between the PL originating from volume states of nanocrystals containing two photoexcited carrier pairs, and the PL due to the silicon oxide states. We discuss also the role of the implant fluence on the PL properties of samples.     

低浓度掺杂CdSe/ZnS量子点光纤光致荧光光谱特性研究

制备了一种半导体量子点CdSe/ZnS低浓度掺杂的光纤,测量了不同掺杂浓度和不同光纤长度下光纤出射端的光致荧光光谱,分析了掺杂光纤长度和浓度对量子点光纤荧光光谱特性的影响.结果表明,与掺入光纤前相比,光纤中的量子点荧光发射峰值波长出现红移.在掺杂光纤长度为1~20 cm和掺杂浓度为(0.33~2.5)×10－2mg/mL的实验范围内,红移量随着掺杂光纤长度的增加和掺杂浓度的提高而增大.对给定的激励功率,荧光发射峰值强度对应有一个最佳的量子点光纤长度.对于给定的量子点光纤长度,荧光发射峰值强度对应有一个最佳的量子点掺杂浓度.     

Influence of excitation light wavelength on the photoluminescence properties for ZnO films prepared by magnetron sputtering

Highly orientated polycrystalline ZnO films were deposited on sapphire, silicon and quartz substrates at room temperature by r.f. magnetron sputtering. Different photoluminescence (PL) spectra were observed when excited with different wavelength light. A UV emission peak (356 nm) and a blue peak (446 nm) were generated for the films on sapphire, silicon and quartz substrates, and only the 446 nm blue emission appeared for the films on glass substrates when the wavelength of the excitation light was 270 nm. With increasing the wavelength of the excitation light up to 300 and 320 nm, the UV emission disappeared for films on various substrates and the wavelength of the PL peaks increased up to 488 and 516 nm, respectively. When the wavelength of the excitation light increased to 398 nm, the PL spectrum becomes a wide band that is consistent with three emission peaks.     

The effect of annealing on the photoluminescent and optical properties of porous anodic alumina films formed in sulfamic acid

Photoluminescent and optical properties of porous oxide films formed by two-step aluminum anodization at a constant potential of 30 V in sulfamic acid have been investigated after their annealing, ranging from room temperature up to 600 °C. X-ray diffraction reveals the amorphous nature of porous oxide films. Infrared and energy dispersive spectroscopy indicates the presence of sulfuric species incorporated in oxide films during the anodization. Photoluminescence (PL) measurements show PL bands in the range from 320 to 600 nm. There are two peaks in emission and excitation spectra. One emission peak is at constant wavelength centered at 460 nm and the other shifts from 390 to 475 nm, depending on excitation wavelength. For excitation spectra, one spectral peak is at constant wavelength at 270 nm and the other also shifts to longer wavelengths while increasing emission wavelength. Upon annealing of the as-prepared oxide films PL increases reaching maximum value at about 300 °C and then decreases. The results indicate the existence of two PL centers, one placed at surface of the pore wall, while the other positioned inside the oxide films.     

Characterization of photoluminescence spectra from poly allyl diglycol carbonate (CR-39) upon excitation with the ultraviolet radiation of various wavelengths

The induced photoluminescence (PL) from the π-conjugated polymer poly allyl diglycol carbonate (PADC) (CR-39) upon excitation with the ultraviolet radiation of different wavelengths was investigated. The absorption and attenuation coefficients of PADC (CR-39) were recorded using a UV–visible spectrometer. It was found that the absorption and attenuation coefficients of the PADC (CR-39) exhibit a strong dependence on the wavelength of ultraviolet radiation. The PL spectra were measured with a Flormax-4 spectrofluorometer (Horiba). PADC (CR-39) samples were excited by ultraviolet radiation with wavelengths in the range from 260 to 420 nm and the corresponding PL emission bands were recorded. The obtained results show a strong correlation between the PL and the excitation wavelength of ultraviolet radiation. The position of the fluorescence emission band peak was red shifted starting from 300 nm, which was increased with the increase in the excitation wavelength. The PL yield and its band peak height were increased with the increase in the excitation wavelength till 290 nm, thereafter they decreased exponentially with the increase in the ultraviolet radiation wavelength. These new findings should be considered carefully during the use of the PADC (CR-39) in the scientific applications and in using PADC (CR-39) in eyeglasses.     

Photoluminescence of multiwalled carbon nanotubes excited at different wavelengths

In this paper the multiwalled carbon nanotubes (MWNTs) were synthesized by a chemical vapour deposition and the SEM graph shows that the sample has good construction. The micro-Raman spectrum shows the characteristic line of the MWNTs and an additional line produced by the defects on the outer surface of MWNTs. The photoluminescence (PL) spectra observed experimentally are variable under different excitation wavelengths and the strong excitation wavelength dependence of luminescence indicates a distribution of emitters which include electron $\pi$ in excited states and the Van Hove singularities. The absorption spectra confirm the transition channels which are consistent with the PL emission.     

Optical properties of alumina membranes prepared by anodic oxidation process

The luminescence property of anodic alumina membranes (AAMs) with ordered nanopore arrays prepared by electrochemically anodizing aluminum in oxalic acid solutions have been investigated. Photoluminescence emission (PL) measurement shows that a blue PL band occurs in the wavelength ranges of 300-600 nm. The PL intensity and peak position of AAMs depend markedly on the excitation wavelength. A new peak located at 518 nm can be observed under a monitoring wavelength at 429 nm in the photoluminescence excitation (PLE) spectra. Convincing evidences have been presented that the PLE would be associated with the residual aluminum ions in the membrane. The PLE and PL of AAMs, as a function of anodizing times, have been discussed. It is found that the oxalic impurities incorporated in the AAMs would have important influences on the optical properties of AAMs in the initial stage of anodization. The PL and PLE spectra obtained show that there are three optical centers, of which the first is originated from the F⁺ centers in AAMs, the second is correlated with the oxalic impurities incorporated in the AAMs, and the third is associated with the excess aluminum ions in the membrane.     

a-C:H薄膜的光致发光

利用射频辉光放电法沉积a-C:H薄膜,研究不同测量温度、不同退火温度光致发光光谱的变化,以及光致发光光谱随光子能量的变化,实验表明:随着测量温度的升高发光效率降低,用非晶碳网络的二相系统模型对这些结果作了解释。另外,光致发光光谱也随着激发光能量的不同而变化,当激发光能量接近光学带隙E_opt时,发光强度最高。 关键词：     

AlN微晶棒的的制备及光致发光性能研究

采用直流电弧放电方法,在无催化剂的条件下直接氮化Al合成纤锌矿结构的AlN微晶棒。分别利用拉曼光谱仪(Raman)、扫描电子显微镜(SEM)和光致发光(PL)谱等测试手段对所制备样品进行表征和发光性能的研究。结果表明:所制备的Al N微晶棒长度约为30μm,直径约为10μm。在AlN微晶棒的PL谱中,有两个主要发光峰,中心在430 nm的发射源于VN和(V_(Al)-O_N)~(2-)构成的深施主-深受主对缺陷发光,中心在650 nm的发射源于VAl形成的深受主能级到价带的缺陷发光。在激发波长由270 nm逐渐增大到300 nm的过程中发现,Al N微晶棒波长在430 nm处的发光峰先增强后减弱,在激发波长为285 nm时强度最大;650 nm处的发光峰随激发波长增大而逐渐增强。     

Luminescence of color centers formed in alkali-earth-doped yttrium orthoaluminate crystals

Alkali-earth-doped yttrium orthoaluminate crystals grown in a reducing atmosphere are found to show bright photoluminescence (PL) in visible wavelength regions under the excitation by UV light source. From the results of transmission, PL, PL excitation and time-resolved PL spectra for the samples with different types and concentrations of dopants and the comparison to the results for the samples grown under different conditions, the origin of principal emission is determined to be color centers stabilized by heterovalent ions. The observed fast lifetime and high quantum yield of the luminescence can be explained by dipole-allowed transition between the levels localized in a vacancy. Comparing the effects on the optical properties from several types of dopant ions and taking influence from the UV irradiation into account, a model for the structure of emission centers is proposed.