共查询到17条相似文献,搜索用时 125 毫秒
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对不同温度退火未掺Cr的纳米结构Al_2O_3块体的荧光谱进行了系统的研究。结果表明,在纳米级勃母石,η-Al_2O_3和γ-Al_2O_3试样中均观察到两个宽的荧光带(p_1和p_2带),它们的波数范围分别为20000—14500和14500—11500cm ̄(-1)。p_1带可归结为纳米Al_O_3,本身所含的微量Cr ̄(3+)离子产生的荧光,这与前人报道的掺Cr的Al_2O_3结果一致,p_2带为未曾见报道的新的荧光带。本文重点对p_2带出现的条件及其机制进行了比较详细的讨论。 相似文献
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在较宽的温度(4.2-80K)和磁场(0-8T)范围内测量了YBa2Cu3O7-δ和Y0.9Eu0.1Ba2·Cu3O7-δ样品的磁滞回线和磁弛豫,研究了其M(t),Jc(T)和Ueff(J)关系,并与现有的一些理论模型所预言的结果进行了比较。结果表明:(1)与YBa2Cu3O7-δ相比,Y0.9Eu0.1·Ba2Cu3O7-δ样品的有效钉扎势和无磁通蠕动时的临界电流密度有明显提高,表明Eu的部分替代引入了新的、具有更大的钉扎势的钉扎中心;(2)与其它模型相比,集体钉扎——蠕动理论对我们的实验结果作了更好的描述,因而本文为这一理论提供了新的实验证据。
关键词: 相似文献
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用卢瑟福背散射/沟道技术研究了1MeVSi+在衬底加温和室温下以不同剂量注入Al0.3G0.7As/GaAs超晶格和GaAs后的晶格损伤。在衬底加温下,观察到Al0.3Ga0.7As/GaAs超晶格和GaAs都存在一个动态退火速率与缺陷产生速率相平衡的剂量范围,以及两种速率失去平衡的临界剂量。超晶格比GaAs更难以损伤,并且它的两种速率失去平衡的临界剂量也大于GaAs中的相应临界剂量,用热尖峰与碰撞模型解释了晶格损伤积累与注入剂量和衬底温度的关系。用CNDO/2量子化学方法计算了GaAs和AlxGa1-xAs中化学键的相对强度,并根据计算结果解释了注入过程中Al0.3Ga0.7As/GaAs超晶格和GaAs中晶格损伤程度的差别。
关键词: 相似文献
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通过制备(YBa2Cu3O7)1-x(V2O5)x(0≤x≤0.15)复合材料,获得了一系列典型的弱连接的颗粒超导体,其中以dR/dT-T关系中呈现出双峰转变为主要特征。第一峰代表晶粒的超导转变,第二峰代表颗粒系统超导长程序的形成。对于具有双峰转变的样品,其临界电流密度一致地符合ic~(1-t)n,n=1.6.这一行为与三维Josephson结网络系统的渗流行为相一致;对于不具有双峰转变的系统,临界电流密度随温度的变化尽管也可以用jc~(1-t)n描述,但是幂指数n明显地大于1.6,且随样品的不同而离散地分布。本文还对产生这种离散的原因进行探索和分析。
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用准分子激光抽运可调谐染料窄带激光测定了室温下NO2分子500—532nm区高分辨荧光激发谱,在两个较强吸收区505—510nm和513—520nm范围内标识了25个振动带,并作了转动分析,得到了相应的带头位置、转动常数和旋-转偶合常数等分子光谱常数,在25个振动带中有5个谱带是新发现的,所有得到转动分析的谱线均属于平行跃迁X~ 2 A1—A~2B2,对实验结果的分析表明电子激发态A~ 关键词:
激光诱导荧光激发谱
振动带
转动分析 相似文献
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The transition intensities of the 4-μm bands of SO2 are measured with high precision using a tunable laser difference-frequency spectrometer. The band strength calculated from the ν1 + ν3 combination band data at 295.2K is Sv0 = 10.54 ± 0.04 cm?2 atm?1. Here the uncertainty (three standard deviations) quoted is for the relative precision only; the absolute accuracy, which depends on the sample pressure calibration, is ~1%. F-factors and “hot” band results are also obtained. 相似文献
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The CF2 absorption spectrum between 2700 and 2250 Å and its fluorescence spectrum excited by radiation near 2500 Å have been observed in matrix isolation experiments. The positions of the absorption bands are somewhat dependent on the environment in which the CF2 molecule is trapped. The absorption spectrum can be explained in terms of a progression in the upper-state bending fundamental, with a band spacing of 499 cm−1, and the fluorescence spectrum involves a progression in the ground-state bending fundamental, with a band spacing of 657 cm−1. A significant deviation between the calculated and observed separation of any given absorption and emission band can be explained by considering the effect of phonon interactions. Arguments are presented suggesting that the band origin lies near 36 900 cm−1 for CF2 produced by the photolysis of CF2N2 in an argon matrix. 相似文献
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From the Shubnikov—De Haas-effect in p-type Sb2 Te3-crystals with carrier concentrations between 8.3 x 1019/ cm3 and 1.2 x 1020/ cm3 a two valence band model was deduced. For the lower band a twelve valley model is proposed, with the maxima located in the trigonal—binary planes. The energy difference between the two bands is derived as approximately 150 meV. 相似文献