Recent Advances in Biophysical／Biochemical／Biomedical Application of Raman Spectroscopy

Examples of some important biophysical,biochemical and biomedical problems that have been uniquely solved by Raman spectroscopy will be illustrated and discussed.The first example concerns the electronic structure,metal-ligand bonding,and reactivity of metalloporphyrins,the synthetic models for the ubiquitous chromophore in hemoproteins.we will demonstrate how off-resonance scattering,electronic resonance enhanced scattering,as well as nonlinear hyper-Raman(three-photon)scattering can provide a highly complementary picture about the effective electronic symmetry and bonding of metalloporphyrins in its electronic ground and excited states.we will illustrate how the bonding information otained from the Raman effect can be useful in understanding the chemical behavior of metalloporhyrin such as its affinity toward exogenous ligand and its preference for the orientation of planar axial ligand(such as imidazole from histidine‘s sidechain).Some paradoxical misconception about the relationship between bond strength and ligand binding affinity will be discussed.Raman spectroscopy,particular with near infraed laser excitation to avoid fluorescence,has been applied successfully to extract significant biochemical information from intact eye lenses.The long-standing cotroversy over the exact nature of the involvement of disulfide cross-linking in lens aging and cataract formation has been settled by the Raman spectroscopy because of its ability for monitoring the sulfhydryl to disulfide reaction of an intact lens in a nondestructive and noninvasive manner.A more recent contribution to the lens biochemistry is the use of Raman spectroscopy for a clear demonstration of the biochemical changes induced by near ultraviolet light in the lens of an animal model,resembling the changes observed in human lens aging and cataract formation.     

Chemical/Biochemical/Biophysical/Biomedical Applications of Raman Spectroscopy

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基于自适应方法的Sn／O／H／N／C／Cl反应机理简化

计算包含详细反应机理的复杂反应流问题仍然是十分费时的,已有的反应流计算方法通常采用简化的化学反应机理.传统的机理简化方法大多基于反应条件的稳态假设,如主量组分分析法等.近年来,一种基于自适应化学理论的机理简化的新方法被提出.该方法根据设定的化学精度要求,可实现详细反应机理的最优简化.对Sn/O/H/N/C/Cl详细反应机理的简化结果表明Sn CO2=SnO CO和Sn O2=SnO O为机理中影响Sn氧化最重要的两个基元反应.     

Tomography Formula for Biochemical Imaging of Thin Tissue with Diffuse-Photon Density Waves

Artificial object detection and segmentation in natural background are key points of pattern recognition and computer vision.The effect of complex texture of natural background and other factors,make it difficult to segment artificial object from natural background.In this paper,an algorithm based on watershed transform and regional fractal texture analysis is proposed to detect and segment artificial object from natural background.     

InAIAs／GaSbAs／InPDHBT与InP／GaSbAs／InPDHBT性能比较分析

双异质结双极晶体管（DHBT）的性能与发射区-基区（E．B）异质结和基区．集电区（B．C）异质结的能带突变类型关系密切,本文基于热场发射．扩散模型,对两类不同能带结构类型的新型DHBT的性能做了比较分析．结论表明：与作为当今研究热点的E．B和B．C异质结构均为全交错II型能带结构的InP／GaSbAs／InPDHBT的性能相比,E．B异质结采用传统I型、B．C异质结采用交错II型的一类新型能带结构的InAlAs／GaSbAs／InPDHBT虽然在开启电压上更高,但具有更好的电流驱动能力、直流增益和高频性能．     

Magnetic behaviour investigation on symmetric spin valves of Co／Cu／NiFe and NiFe／Cu／Co

In this paper,we have obtained and investigated the magnetic behaviours of the ferromagnetic layer in the symmetric spin valves of Co/Cu/NiFe and NiFe/Cu/Co by measuring with a vibrating sample magnetometer and analysing in terms of the multi-domain Ising models.It has been found that some magnetic layer can have quite different magnetic behaviours in different structures of spin valves,depending on the properties of the under-layer.In our investigation,we have found that the magnetic behaviour of a Co layer depends mainly on the magnetization of the under-layer,whereas this is not the case for the NiFe layer.     

808nmInGaAsP／InGaP／GaAs激光器列阵

研制出３０个单元的ＩｎＧＡａＳｐ／ＩｎＧａＰ／ＧａＡｓ分别限制双异质结单量子阱激光器列阵,器件外微分量子效率达７８％,发向波长８０８ｎｍ,准连续输出的光功率达２７Ｗ。     

Gallavotti–Cohen-Type Symmetry Related to Cycle Decompositions for Markov Chains and Biochemical Applications

We slightly extend the fluctuation theorem obtained in (Lebowitz and Spohn in J. Stat. Phys. 95:333–365, 1999) for sums of generators, considering continuous-time Markov chains on a finite state space whose underlying graph has multiple edges and no loop. This extended frame is suited when analyzing chemical systems. As simple corollary we derive by a different method the fluctuation theorem of D. Andrieux and P. Gaspard for the fluxes along the chords associated to a fundamental set of oriented cycles (Andrieux and Gaspard in J. Stat. Phys. 127:107–131, 2007).     

半导体超晶格的多声子拉曼散射研究

半导体超晶格的多声子拉曼散射研究／张树霖，杨昌黎，侯勇田（北京大学物理系北京１００８７１）彭中灵，李杰，袁诗鑫（中科院上海技物所上海２０００８３）Ｒ．Ｐｌａｎｅｌ（ＭｉｃｒｏｓｔｒｕｃｔｕｒｅｓａｎｄＭｉｃｒｏｅｌｅｃｔｒｏｎｉｃｓＬａｂｏｒａｔｏｒ...     

The Application of New Technology for Raman Spectroscopy

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Multiphonon resonant Raman scattering in GaSe

Multiphonon resonant Raman scattering up to 4 phonons in GaSe has been measured. The results are interpreted by a simple cascade theory. It is shown that the dispersion of RRS here is dominated by resonances with the exciton states.     

Tunable Photoluminescence Spectra of Doped Semiconductor Superlattices

Taking into account the density state tails appearing due to fluctuations of impurity concentrations, the spontaneous emission spectra of doped semiconductor superlattices are calculated. In the framework of the model developed, the explanation of the experimentally observed longwave edge and the shift of the photoluminescence spectra with increase in the excitation level and temperature is given. The role of the defects formed on -irradiation is discussed, and the lifetime of current carriers is evaluated depending on the design parameters and excitation conditions of the GaAs doped superlattices.     

Nonlinear Optical Processes in Doped Semiconductor Superlattices

For doped semiconductor superlattices we have analyzed the effects of absorption saturation and change in the refractive index depending on the level of their excitation and structure parameters. The calculations were carried out with account for the tails of the density of states and screening of the electrostatic potential. It is shown that doped superlattices may display shading, i.e., the increase in the absorption coefficient at a fixed frequency with increase in light intensity. For –doped superlattices a stronger nonmonotonicity of the change in the refractive index with increase in the excitation level in comparison with typical structures can manifest itself.     

Multiphonon Raman scattering and gap states in cis-polyacetylene

The different features of the Raman scattering in resonance with electronic absorption band in cis and trans-polyacetylene are discussed. The strong multiphonon scattering observed in cis-polyacetylene is accounted for in terms of a localized gap state, which dominates the scattering process near the absorption edge.     

Multiphonon Raman scattering from individual single-walled carbon nanotubes

Combinations of up to 6 zone-edge and zone-center optical phonons are observed in the Raman spectra of individual single-walled carbon nanotubes (SWNTs). These multiphonon Raman modes exhibit distinct signatures of the one-dimensional nature of SWNTs and provide information on the phonon structure, exciton-phonon coupling, and excitonic transitions in nanotubes.     

关于半导体极薄层超晶格拉曼散射特征的研究

关于半导体极薄层超晶格拉曼散射特征的研究杨昌黎，张树霖（北京大学物理系北京１００８７１）Ｒ．Ｐｌａｎｅｌ（ＬａｂｏｒａｔｉｒｅｄｅＭｔｃｒｏｓｔｒｕｃｔｕｓｅｄｅｔｄｅＭｉｃｒｏｅｌｅｃｔｒｏｎｉｑｕｅＣｅｎｔｒｅＮａｔｉｏｎａｌｄｅｌａＲｅｃｈｅｒ...     

Current Oscillation and dc-Voltage-Controlled Chaotic Dynamics in Semiconductor Superlattices

We report a detailed theoretical study of current oscillation and dc-voltage-controlled chaotic dynamics in doped GaAs/AlAs resonant tunneling superlattices under crossed electric and magnetic fields. When the superlattice is biased at the negative differential velocity region, current self-oscillation is observed with proper doping concentration. The current oscillation mode and oscillation frequency can be affected by the dc voltage bias, doping density, and magnetic field. When an ac electric field with fixed amplitude and frequency is also applied to the system, different nonlinear properties show up in the external circuit with the change of dc voltage bias. We carefully study these nonlinear properties with different chaos-detecting methods.