Modeling and Calculation of the Dynamics of Spectra with Allowance for Isomerization of Complex Molecules

A semiempirical parametric method for modeling of dynamic (time-resolved) electron-vibrational spectra of complex molecules with allowance for isomer-isomer transformations is proposed. It is based on the method developed earlier for construction of three-dimensional spectra of complex molecules without regard for isomer-isomer transformations. All the matrix elements necessary for calculation of spectra can be determined by the methods developed earlier. The time dependence of the population of a large number of vibronic levels has been determined using the iteration numerical method of integrating kinetic equations. Handy computational algorithms and a specialized software for a personal computer have been developed. The computer experiments conducted have shown that the method proposed can be used for modeling of dynamic spectra of complex molecules with allowance for their isomer-isomer transformations in the real-time scale.     

Simulation of the Processes of Isomerization of Complex Molecules and of Their Spectra with Time Resolution

Based on the method developed earlier to calculate the dynamic electronic-vibrational spectra of complex molecules with allowance for isomeric transformations, a more general method has been developed making it possible to model the spectra of several isomeric forms in any number depending on the problem posed. Population dynamics analysis of the energy levels of isomers is possible. Computational algorithms have been developed and optimized, and a specialized software has been developed for a PC and a supercomputer (of the type MVS 1000). Computer experiments were carried out, and the possibility of simulating dynamic spectra and kinetic intramolecular processes in real time for complex compounds with allowance for their intermolecular transformations is shown.     

Modeling of the Kinetics of Intramolecular Processes and Transient Spectra with Allowance for Nonradiative Transitions

It has been shown that the kinetics of intramolecular processes and time-resolved spectra with allowance for the quantum beats of the resonant states of isomers or isolated subsystems of levels of one isomeric form can be described with the use of a molecular model interpreting the effect of beats as a nonradiative transition. We have obtained an expression for the nonradiative transition probability, which is directly proportional to the beat frequency and depends oscillatorily on time, thus modeling the effect of beats. The parameter of the molecular system model is the beat frequency directly related to the parameter characterizing the intramolecular interisomeric interactions (the corresponding nondiagonal element of the energy matrix) rather than the value of the nonradiative transition probability. The character of the change in the level populations and, accordingly, in the band intensities in the spectra in the proposed model is in good agreement with the experiment, including the fine structure of the time dependences — oscillations of the line intensities. In analyzing the temporal experiment with a high resolution, it is necessary to take into account the instrument function leading to quantitative and qualitative changes in the time dependences. The traditional model of nonradiative transitions with a constant probability value has a very limited range of applicability — very high beat frequencies compared to the probability of optical transitions.     

泵浦-探测技术中受激量子拍的理论研究

基于V型三级级原子由于真空与原子耦合引起的量子相干效应,研究了泵浦-探测技术中透射受激量子拍特征.理论计算表明:这种受激量子拍与荧光量子拍相比具有高的信噪比.理论结果与实验有较好的一致性.     

Frequency Spectra of Quantum Beats in Nuclear Forward Scattering of 57Fe: The Mössbauer Spectroscopy with Superior Energy Resolution

Frequency spectra of quantum beats (QB) in nuclear forward scattering (NFS) are analysed and compared to Mössbauer spectra. Lineshape, number of lines, sensitivity to minor sites, and other specific properties of the frequency spectra are discussed. The most characteristic case of combined magnetic and quadrupole interactions is considered in detail for ⁵⁷Fe. Pure magnetic Zeeman splitting corresponds to a eight-line spectrum of QB, six of which show the same energy separation as the six lines in Mössbauer spectra. Two other lines (called 2′ and 3′) are the lower-energy satellites of the lines 2 and 3. As the quadrupole interaction E _Q appears, the satellites remain unsplit in the quantum beat frequency spectra, as well as the first (zero-frequency) and the 6th (largest frequency) lines. Each of the lines 3 and 5 generates a doublet split by 2E _Q, and the lines 2 and 4 generate triplets. In QB frequency spectra (QBFS) of thin absorbers of GdFeO₃ we demonstrate the enhanced spectral resolution compared to Mössbauer spectra. Small particle size in an antiferromagnet (Fe₂O₃) was found to affect the QBFS via enhancement of the intensity around zero-frequencies. An asymmetric hyperfine field distribution mixes up into the hybridization with dynamical beats, which enlarges the frequencies of the low-lying QBFS lines and makes their shifts relatively large compared to the shift of the highest-frequency line.     

CdSeS量子点的光吸收谱亚结构和光致发光激发谱分析

用光致发光激发(PLE)谱分析吸收谱的亚结构。实验样品是共熔法制备的CdSeS量子点玻璃,量子点的生长时间分别为2h和4h,高分辨透射电子显微镜(HRTEM)分析得到样品中量子点的平均直径分别为3．6nm和3．8nm。在室温下对样品进行了光吸收谱和光致发光激发谱研究。光吸收谱显示了量子尺寸效应,光致发光激发谱中低能端有两个明显的峰。考虑价带简并以及电子与空穴之间的相互作用,通过理论分析和数值计算,得到1S3/2-1Se和2S3/2-1Se的跃迁能量及其随量子点半径的变化,由此确认光致发光激发谱中的两个峰分别为1S3/2-1Se和2S3/2-1Se跃迁。     

Theoretical models for interisomer transitions of complex molecules and their spectral manifestations

We have used computer simulation to compare theoretical models for describing interisomer transitions of complex molecules and their spectral manifestations. We have shown that the kinetics of the intramolecular processes and time-resolved spectra, taking into account quantum beats between resonant (bound) states of the isomers (or isolated level subsystems for one isomer form), can be described not only by using a general molecular model in which the resonant levels of the subsystems act as a single level of a mixed state, with a time-dependent wave function in the form of quantum beats, but also by using a model interpreting the beat effect as a nonradiative transition. These models are completely equivalent: the parameters describing them have the same values, and numerical differences in the results obtained are no greater than 1% and are due to numerical round-off errors in the calculations and not differences between the models. The second model is preferred because it is graphically clear and conventionally used for describing and interpreting intramolecular processes, but it does take somewhat longer (∼10%) to run the simulation. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 36–41, January–February, 2006.     

Macroscopic Quantum Electrodynamics of a Plasma Model: Derivation of the Vlasov Kinetics

We derive the large-scale Vlasov kinetics of a plasma model from its underlying quantum electrodynamics. The model comprises a system of nonrelativistic electrons, coupled to a quantised electromagnetic field and to a passive, positively charged, neutralising background.     

Subdiffusive Quantum Transport for 3D Hamiltonians with Absolutely Continuous Spectra

We exhibit a class of Hamiltonians in dimension D3, describing a quantum particle in an aperiodic medium with absolutely continuous spectrum and subdiffusive behavior. The diffusion exponent, which characterizes the time growth of the mean square displacement, can be chosen slightly bigger than Guarneri's lower bound. These models are built out of 1D Hamiltonians with well-understood spectral and transport properties.     

电场调控下不对称耦合量子点中激子的发光特性

使用有效质量模型,从理论上对GaAs/A10.35Ga0.65As不对称耦合量子点在不同耦合强度下束缚态和反束缚态的能级分裂情况进行了详细分析,重点探讨了电子和空穴的耦合隧穿对量子点体系能级特征及激子发光强度的影响.研究发现:不对称耦合量子点在外电场作用下价带束缚态和反束缚态能级出现反交现象,反交处的能级分裂值和临界电...     

基于谷胱甘肽配体的ZnSe量子点对pH响应的时间分辨荧光光谱特性

当前,有关量子点pH响应方面的研究主要集中在含Cd（镉）类量子点,且都是研究其稳态荧光光谱对pH值的响应。然而,Cd类量子点对生物体系具有一定的毒性,且稳态荧光光谱法由于受浓度等因素的影响具有一定的不稳定性,因此应用于生物体系中作为pH探针具有明显的缺点。基于以上分析,通过水相合成法,我们制备出了基于谷胱甘肽配体的水溶性ZnSe量子点,该量子点具有毒性小,生物兼容性好等特点,适合被应用于生物体系中。利用所制备的ZnSe量子点,采用时间相关单光子计数技术,结合紫外可见吸收光谱和稳态荧光光谱,对pH值在5~11不同环境下的ZnSe量子点荧光动力学进行了系统性的研究。ZnSe量子点荧光衰减具有两个寿命组分,拟合得到分别为4和24 ns。通过采集不同探测波长下ZnSe量子点荧光衰减曲线,发现其长寿命组分随探测波长的增加而增加,而短寿命组分基本不随探测波长的改变而改变,结合有关报道分析判断,短寿命和长寿命组分分别来源于核内非局域载流子复合和表面态局域载流子复合。实验发现,处于不同pH值的环境下的ZnSe量子点具有不同的荧光寿命,其荧光寿命与pH值的变化呈负相关。通过比较ZnSe量子点两种荧光寿命组分随pH值的变化关系,发现ZnSe量子点的荧光寿命对pH值的响应主要来源于长寿命组分即表面态寿命,且在不同pH值范围内响应的灵敏度不同,在6~8的pH值范围内响应最为显著,表现为长寿命组分随pH值的增加出现一个较大幅度的衰减。实验进一步发现,ZnSe量子点两个寿命组分的比值在不同pH值范围内具有较好的线性相关性,但在不同pH值范围内斜率不同,通过比较,最大值在pH值为6~8的范围内。另外,与金属钠离子相互作用实验及相关报道表明,金属离子对ZnSe量子点荧光寿命的影响较小。以上研究表明,ZnSe量子点在生物体系pH值检测中具有良好的应用前景。     

Nonrelativistic Quantum Mechanics with Spin in the Framework of a Classical Subquantum Kinetics

Recently it has been shown that the spinless one-particle quantum mechanics can be obtained in the framework of entirely classical subquantum kinetics. In the present paper we argue that, within the same scheme and without any extra assumption, it is possible to obtain both the nonrelativistic quantum mechanics with spin, in the presence of an arbitrary external electromagnetic field, as well as the nonlinear quantum mechanics.     

Multipartite Quantum Coherence and Distribution under the Unruh Effect

Quantum coherence of the tripartite W state and Greenberger–Horne–Zeilinger (GHZ) state under the Unruh effect are explored based on the model of a two‐level detector qubit coupled to a massless scalar field. The results reveal that Unruh thermal noise really destroys tripartite quantum resources. It is worth mentioning that the quantum coherence of the GHZ state reaches zero in the infinite acceleration limit, but that of the W‐state always remains nonzero. Coherence of the GHZ state displays a sudden death as the coupling parameter grows, while coherence freezing can be witnessed for the W state. It can be concluded that the W state is more robust than the GHZ state against Unruh radiation. Moreover, the related investigation can be expanded to N‐qubit quantum systems and the corresponding analytical solution is obtained. It indicates that the larger number W‐type entangled qubit can be as a better quantum resource for quantum information tasks under the Unruh effect.     

用积分法推导NEA光电阴极的量子产额

以“三步发射模型”为基础, 采用积分的方法推导出反射式和透射式负电子亲和势（ Ｎ Ｅ Ａ）光电阴极的量子产额表达式, 其中反射式阴极的表达式和传统的求解扩散方程得出的表达式完全相同, 而根据透射式阴极的表达式绘出的量子产额理论曲线, 和求解扩散方程绘出的曲线基本重合, 与实验曲线也符合得很好。     

Energy Spectra of a Magnetic Quantum Ring with an Off-Center Impurity

In this paper, we calculate the low-lying spectra of a single-electron magnetic quantum ring with an offcenter Coulomb impurity, where the magnetic field is zero within the ring and constant elsewhere. The impurity, either an acceptor or a donor, is located at a distance d as measured from the plane of the ring along the vertical z direction.The magnetic moments are found in order to get visible discontinuities at the points of the ground-state orbital angular momentum L transitions induced by magnetic fields.     

神经网络法研究多溴代二苯胺热力学性质

通过时间分辨光谱技术详细地研究了ZnCuInS/ZnSe/ZnS量子点的激子弛豫动力学. 基于速率分布模型,波长依赖的发射动力学表明本征激子、界面缺陷态中的激子、给-受体对态中的激子都会参与量子点的发光过程,整个发光过程主要依赖于给-受体对态发射. 瞬态吸收数据表明激发后本征激子和界面缺陷物种可能会同时出现,在高激发光强下,光强依赖的俄歇复合过程也存在于量子点中     

温度对CdSe/znS量子点吸收光谱和光致发光谱的影响

测量了分散于正己烷溶液和甲苯溶液中的CdSe/ZnS量子点在室温到近溶液沸点温度间的吸收与光致发光光谱,比较了两种不同的CdSe/ZnS量子点的光谱特性,讨论了温度对吸收和光致发光光谱峰值波长以及相对强度的影响。结果表明:在25~100℃范围内,CdSe/ZnS量子点激子吸收峰波长有微小红移,最大约为4nm;光致发光光谱峰值波长略有红移,但最大不超过6nm。根据光致发光光谱测量的结果,确定了Varshni定律中关于CdSe/ZnS量子点禁带宽度的两个经验参数:α=(2.0±0.2)×10^-4eV/K和β=(200±30)K。温度对CdSe/ZnS量子点吸收强度影响不大,荧光发射强度与温度呈线性关系增强。     

四氨基钴酞菁的分子结构和红外光谱量子化学研究

四氨基钴酞菁作为一种很有前途的光敏剂,其光谱研究具有十分重要的意义。以密度泛函的B3LYP/3-21G*方法对四氨基钴酞菁的四种构型进行结构优化,计算出最稳定结构的能量,并模拟计算四氨基钴酞菁的红外光谱,模拟得出的红外光谱与实验所得的振动带有很好的拟合性。     

量子限制斯达克效应对三角形量子阱吸光特性的影响

本文通过计算量子力学波动方程以及载流子传输特性,哈密顿量的H能谱图和边界条件等的理论方法来分析量子限制斯达克效应对三角形量子阱体系吸收特性的影响,说明了选择合适的量子阱垒层对于提高三角形量子阱吸光率具有重要的意义。