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1.
The spontaneous emission decay dynamics of a tripod configuration four-level atom driven by a single laser field is studied. Under different initial conditions, we discuss the effects of quantum interference and detuning of external driving field on atomic spontaneous emission properties. For the larger detuning, the interesting phenomena of the spectral line narrowing are found which stem from the contribution of external driving field. 相似文献
2.
应用 Von Neumann熵 和 Schmidt number K两种纠缠度量讨论了各向异性光子晶体中二能级原子和自发辐射场间纠缠度的演化性质. 研究发现,原子-光场纠缠度的演化与原子上能级和光子晶体能带带边的相对位置有关,当原子上能级处于光子晶体禁带内,原子-光场纠缠度将保持稳定,当原子上能级处于光子晶体能带中,原子-光场纠缠度先增大后衰减到零. 纠缠度的大小还与原子的初态有关. 可以通过控制原子的初态和原子上能级与带边的相对位置来控制原子-光场纠缠度的演化特性. 相似文献
3.
This paper demonstrates experimentally and numerically that a significant modification of spontaneous emission rate can be achieved near the surface of a three-dimensional photonic crystal. In experiments, semiconductor core-shell quantum dots are intentionally confined in a thin polymer film on which a three-dimensional colloidal photonic crystal is fabricated. The spontaneous emission rate of quantum dots is characterised by conventional and time-resolved photoluminescence (PL) measurements. The modification of the spontaneous emission rate, which is reflected in the change of spectral shape and PL lifetime, is clearly observed. While an obvious increase in the PL lifetime is found at most wavelengths in the band gap, a significant reduction in the PL lifetime by one order of magnitude is observed at the short-wavelength band edge. Numerical simulation reveals a periodic modulation of spontaneous emission rate with decreasing modulation strength when an emitter is moved away from the surface of the photonic crystal. It is supported by the fact that the modification of spontaneous emission rate is not pronounced for quantum dots distributed in a thick polymer film where both enhancement and suppression are present simultaneously. This finding provides a simple and effective way for improving the performance of light emitting devices. 相似文献
4.
Considering two identical two-level atoms interacting with a single-model dissipative coherent cavity field without rotating wave approximation, we explore the entanglement dynamics of the two atoms prepared in different states using concurrence. Interestingly, our results show that the entanglement between the two atoms that initially disentangled will come up to a large constant rapidly, and then keeps steady in the following time or always has its maximum when prepared in some special Bell states. The model considered in this study is a good candidate for quantum information processing especially for quantum computation as steady high-degree atomic entanglement resource obtained in dissipative cavity. 相似文献
5.
海洋沉积物含水率对部分碱金属及碱土金属元素含量的影响及意义 总被引：1，自引：0，他引：1
利用电感耦合等离子体光谱仪(ICP-AES)对海洋表层沉积物及上覆海水、海洋沉积物国家标准物质、陆地的水系沉积物及土壤国家标准物质进行检测以对比海洋沉积物含水率对部分碱金属及碱土金属元素分析结果所造成的影响。结果显示海洋沉积物含水率对钠离子影响最大,往往有超过50%的钠离子来自其中所含海水的贡献,而海洋沉积物含水率对钾、钙、镁的影响则较为微弱。因此,研究海洋沉积物化学组分时有必要考虑其所含海水对钠含量的贡献,以期达到不同海洋沉积物化学组分的可比性。 相似文献
6.
报道了用王水-HF溶样,ICP-AES同时测定海洋沉积物中18种常量、微量元素的方法.该方法简便、快捷,其准确度、精密度及检出限均好. 相似文献
7.
The determination of trace amounts of inorganic elements by electrothermal atomic absorption spectrophotometry (ETA-AAS) or inductively coupled plasma atomic emission spectrometry (ICP-AES) suffers from some kinds of interference due to the inorganic fraction of the matrix of many environmental samples. The ratio between a major matrix element and the analyzed trace element plays an important role in the spectrochemical behaviour of the latter. The resulting enhancing or depressing effect also gives rise to severe faults when the well known standard addition method (SAM) is used. The present work shows the interactions due to the presence of elements such as calcium, sodium, potassium, magnesium and iron during the spectrochemical determinations of trace amounts of cadmium in marine mussels. A possible liquid anion exchange extraction is suggested for the analysis of cadmium by ETA-AAS. 相似文献
8.
单道扫描电感耦合等离子发射光谱的内标元素选择的灰色关联分析再研究(英文) 总被引：1，自引：0，他引：1
应用动态灰色模型（ＧＭ）的灰色关联分析（ＧＩＡ）为单道扫描（ＳＣＳ）电感偶合等离子发射光谱（ＩＣＰＯＥＳ）选择内标（ＩＳＴＤ）。经发射强度序列的ＧＩＡ计算和关联度序列优化后,Ｇｅ ２１９．８７ 被指定为内标。应用内标法和无内标法对中华人民共和国标样ＧＢ０７２３２ 的各元素的分析结果的相对百分误差范围分别为：０．８％ ～７．５％ 和２．５％ ～１７．５％ 。变更系数（ＣＶ）范围分别为：０．７％ ～２．９％ 和２．０％ ～５．８％ 。对内标选择与平均关联度的关系,Ｇｅ ２１９．８７ 特征的某些具体问题及统计相关分析与灰色关联分析在内标选择计算中的不可替代性问题,亦进行讨论 相似文献
9.
研究了以InAs量子点为有源区的二维GaAs基光子晶体微腔的设计与制作,测试并分析了室温下微腔的光谱特性.观察到了波长约为1137 nm,谱线半高宽度约为1 nm的尖锐低阶谐振模式发光峰.我们比较了不同刻蚀条件下光子晶体微腔的发光谱线,结果表明空气孔洞截面的垂直度是影响光子晶体微腔发光特性的重要因素之一.通过调节干法刻蚀工艺,改变空气孔半径与晶格常数的比率,可以在较大范围内调节谐振模式发光峰位置,达到谐振模式与量子点发光峰调谐的目的. 相似文献
10.
11.
顺序扫描ICP—AES法测定海洋沉积物中九种主要成分 总被引：2，自引：0，他引：2
用ICP—AES法测定海洋沉积物中铝、铁、钙、镁、钠、钾、钦、锰、磷等九种主要成分,方法简便,省时省力,测量精密度小于4％,可以满足海洋地球化学的要求。 相似文献
12.
用电感耦合等离子体原子发射光谱仪 (ICP AES)和石墨炉原子吸收光谱仪 (GAAS)分别测定河蚬样品中镉和铬的含量 ,以比较不同测试方法对这两种重金属测定的影响。结果表明 :2种测试法对生物样品中镉和铬含量的测定结果都有显著的影响 ,同一样品中镉和铬含量的ICP AES测定值均显著高于其相应的GAAS测定值。相比ICP AES法 ,GAAS法对河蚬样品中镉和铬含量的测定更为准确。不同方法测定的镉和铬含量的差异程度分别为 1 8.8%和1 36.4 %。本研究显示 :不同测试法对铬含量测定结果的影响比对镉含量测定结果的影响更大。 相似文献
13.
Elemental compositions are measured in manganese nodules collected from the Northern Mid-Pacific floor by inductively-coupled plasma atomic emission spectrometry (1CP-AES) and their growth rates are determined by radiometric methods. The result shows that depth distributions of elements in nodules vary with depth as follows; (i) increase, (ii) decrease and (iii) fluctuation. These internodule variations in elemental compositions are considered to be caused by diffusion and migration of elements in nodules and heterogeneities in textures of nodules. In the present paper, a diffusive model is used to elucidate the inward-increase profile of some elements in nodules. The effective diffusive coefficients are estimated to be of the order of 10-9 cm2/a for Ni, V and Zn in the nodules, which is less than the value reported for radionuclides. 相似文献
14.
Sediments of the Krka River Estuary on the eastern Adriatic coast have been analysed for trace metals after sediment fractionation by sequential leaching. Trace concentrations of Mn, Cu, Pb, Zn, Ni, Co, Cr, V and Ga have been determined by atomic emission spectroscopy. The distribution patterns of the investigated elements follow the expected geochemical partitionings, while minor variations may be caused by early diagenetic effects and variable sediment texture. Taking into account the natural background levels of the investigated elements, the sediments reflect, at present, no significant industrial pollution or anthropogenic input of trace metals into the estuary. 相似文献
15.
Mnica V. Orellana Timothy W. Petersen Alan H. Diercks Samuel Donohoe Pedro Verdugo Ger van den Engh 《Marine Chemistry》2007,105(3-4):229-239
Dissolved organic matter (DOM) is a major carbon reservoir for the global carbon cycle, and its molecules play a key role in the biogeochemistry of the ocean. Colloidal DOM macromolecules assemble to form polymer hydrogels known as marine microgels. Marine microgels represent one of the most dynamic pools of organic carbon in the ocean. However, their optical characteristics and their contribution to ocean optical properties are largely unknown. In this work, we explore the optical and proteomic properties of spontaneously assembled DOM polymer microgels. Microgels from cultures and from Puget Sound seawater were sorted and counted using a dual-laser (365 nm/365 nm) high-speed cell sorter. This sorter has been adapted to interface with a scanning monochromator to measure the fluorescence emission spectrum of the microgels over the range from 300 to 850 nm. Surprisingly, the microgels show a broad fluorescence emission from 420 to 520 nm when excited with UV light. The microgels were classified according to their blue autofluorescence, and by three criteria that are used to define microgels: 1) staining with chlortetracycline 2) the ability to undergo phase transitions at low pH, and 3) dispersion following calcium chelation by EDTA. 相似文献
16.
We investigate the entanglement dynamics via the concurrence of two distant atoms interacting off-resonantly with two cavity fields in Fock states, respectively. We find that the evolution of entanglement has sudden death and sudden birth phenomena, that with the increase of photon numbers in the two cavities, the alternate frequency of sudden death and sudden birth turns fast, and that the amplitude of concurrence oscillates regularly with oscillation frequency becoming slow when the cavity fields have the same photon numbers. While, the maximum of concurrence declines and the amplitude of concurrence oscillates irregularly when the two cavity fields have different photon numbers. In addition, we find the length of death time is dependent on the initial entanglement. 相似文献
17.
In this paper, the samples of sediments collected from five sampling-stations in the river-sea water mixing zone of the Zhujiang Estuary have been determined by the sequencial extraction procedure, anodic stripping voltammetry and atomic emission spectrometry etc. The contents of the heavy metals Zn, Cu, Pb and Cd in the various phases which are dissolvable, ion-exchangeable, combined with carbonates, easily-reducible, reducible, combined with organic matters and sulfides and residue in the sediments, have been obtained. 相似文献
18.
从拉曼峰强着手,得到了键伸缩模式与全耦合模式两种不同计算条件下,亚乙基硫脲(ethylene thiourea,ETU)分子的键极化率,并比较分析了两种计算结果的异同.研究表明:在键伸缩模式的算法中,仅考虑势能分布中键对称伸缩比重相对较大的部分拉曼峰参与极化率计算,显然忽略了键伸缩与键弯曲间的相互耦合,造成了与弯曲振动耦合较强的部分键伸缩极化率值存在一定误差.因此,此方法虽能使问题简化,但却丢失了一些信息.而全耦合模式算法考虑了所有振动模式(键伸缩与键弯曲)相互影响的情况,能更全面的反映键电荷的分布情况, 相似文献
19.
Acoustic reflection profiling data display is traditionally done with the aid of a facsimile type of recorder. It is not uncommon to record the unprocessed acoustic data on a tape recorder for subsequent playback through a laboratory computer. This still involves the use of some sort of facsimile recorder for the ultimate display of profiles. This paper presents the results of a study to adapt a high-speed digital dot matrix plotter for the ultimate display in place of the conventional facsimile recorder. Because a minicomputer drives the display directly, a host of signal conditioning procedures are permitted, with the final display being generated in real time. Algorithms are developed to control the marking density, allow adaptive threshold control, bottom tracking, automatic gain control, and de-emphasis of water column boundary reverberation. These techniques are just a few of the many that can be employed since the computer can readily be carried on a large ship in deep water, or a small vessel in a harbour. Shallow water is the difficult case for high energy acoustic sources because the water column boundaries behave much like an excited acoustic cavity. For this reason, a section of seismic profile is shown which was obtained with a 7·5 kHz pinger in only 8 m of water in Narragansett Bay. This research was partiallysupported by the Division of Computer Research of the National Science Foundation. 相似文献
20.
在正色散掺铒光纤激光器中,利用非线性偏振旋转技术实现自启动锁模,得到了具有极大光谱宽度的高能量、无波分裂耗散型脉冲.该耗散型脉冲的形成是腔内增益、损耗、非线性偏振旋转、正色散和其他非线性效应等共同作用的结果,其形成机理与传统的负色散激光器完全不同.当抽运功率为500 mW时,该类型脉冲的光谱覆盖了1530—1660 nm范围,半高全宽光谱宽度可达42 nm以上.脉冲具有极大的正啁啾,其时间带宽积为483,而单脉冲总能量最大可达34.4 nJ. 相似文献