Anomalous absorption line in the magneto-optical response of graphene

The intensity as well as position in energy of the absorption lines in the infrared conductivity of graphene, both exhibit features that are directly related to the Dirac nature of its quasiparticles. We show that the evolution of the pattern of absorption lines as the chemical potential is varied encodes the information about the presence of the anomalous lowest Landau level. The first absorption line related to this level always appears with full intensity or is entirely missing, while all other lines disappear in two steps. We demonstrate that if a gap develops, the main absorption line splits into two provided that the chemical potential is greater than or equal to the gap.     

Optical absorption and refractive index of a donor impurity in a three-dimensional quantum pseudodot

The optical absorption and refractive index of a donor impurity confined by a three-dimensional quantum pseudodot are studied using the matrix diagonalization method within the effective-mass approximation. The great advantage of our methodology is that it enables us to tune confinement strength and regime by varying two parameters in the model potential. Based on the computed energies and wave functions, the linear, third-order nonlinear and total optical absorption coefficients as well as the refractive index changes have been examined. The results are presented as a function of the incident photon energy for the different values of the chemical potential of the electron gas and the zero point of the pseudoharmonic potential. We find that the larger optical nonlinearity will be obtained by varying the zero point of the pseudoharmonic potential compared to the chemical potential of electron gas.     

基于化学势的吸收过程热力学分析

溴化锂浓溶液对水蒸气的吸收与凝结的热力学过程,一般都用浓度梯度这个驱动势(Fick定律)来分析,但这并不完善。而化学势是引起质传递的真正驱动势,本文基于化学势这一理论对水蒸气的被吸收过程进行了热力学分析,得出蒸发器的水蒸气虽温度低于喷淋溶液的温度,但它的化学势高于溶液中水的化学势,所以被溶液吸收,且溶液温度(浓度)越高化学势差值越大,水蒸气越易被吸收,针对这一特点,本文提出了对吸收器设计的改进意见。     

Controlling theoretically total absorption in hybrid-cavity resonator with one graphene monolayer outside cavity

Total absorption is realized theoretically in a graphene-outside-cavity resonator. The structure is composed of the FP-Fano hybrid resonance cavity. Changing the thickness of grating exciting Fano resonance, the absorption-mode number can be tuned effectively. For the focused double-mode absorption, the resonances behave insensitively with the variation of chemical potential of graphene. Varying the geometry of grating can control the coupling extent of two modes. Also, by manipulating the period number of two-side multilayers around graphene, the absorption, shift and number of modes are governed.     

Design of a type of broadband metamaterial absorber based on metal and graphene

In this paper, we demonstrate a kind of broadband metamaterial perfect absorber using both graphene and metal resonator elements. Through step by step design and simulation, wider absorption band from about 4.22 THz to 7.48 THz with average absorption rate up to 98.21% is achieved in the absorption spectrum. In addition, the absorber has characteristics of polarization insensitivity and wide incident angle due to its inherent rotational symmetry. Moreover, the absorption band can be adjusted by changing the chemical potential of the graphene. The superiorities of broadband, high absorption rate, polarization independent and wide-angle characteristics make it have potential application prospects in electromagnetic wave absorbing, signal sensing and detection, and other optoelectronic devices.     

Optical properties of a donor impurity in a two-dimensional quantum pseudodot

We investigate the linear and nonlinear optical properties of a donor impurity confined by a two-dimensional pseudoharmonic potential both including harmonic dot and antidot potentials in the presence of a strong magnetic field. Calculations are made by using the perturbation method and the compact density-matrix approach within the effective-mass approximation. Based on the computed energies and wave functions, the linear, third-order nonlinear and total optical absorption coefficients as well as the refractive index changes have been examined. The results are presented as a function of the incident photon energy for the different values of the chemical potential of the electron gas and the zero point of the pseudoharmonic potential. The results show that the optical properties of a donor impurity in a two-dimensional pseudoharmonic QD are strongly affected by the zero point of the pseudoharmonic potential, the chemical potential of the electron gas and the Coulomb interaction.     

K-shell double core-hole spectroscopy in molecules

A great deal of attention has been devoted in the last few years to photoionization processes in isolated molecules leading to the formation of double core-hole (DCH) states. There are two main experimental avenues to induce such processes, namely single-photon absorption followed by the simultaneous ejection of two core electrons, and x-ray-induced multiphoton processes leading to the production of DCH states via the sequential absorption of two soft x- ray photons on a time scale on the order of the molecular Auger lifetime (4–8 femtoseconds for light elements). The formation of molecular two-site (ts) DCH states, in particular, shows great potential as a powerful tool for chemical analysis. A compelling motivation for the study of ts-DCH states is their ability to probe the local chemical environment more sensitively than either single core-hole (SCH) or single-site (ss) DCH states. The enhanced sensitivity originates from the fact that the double ionization potential (DIP) of ts-DCH states is directly coupled to induced changes in the valence charge distribution at the two different atomic sites. Here a review of the recent literature is presented on both types of experiments, and on the related theoretical work.     

富勒烯C_(60)及其电荷转移配合物的吸光、发光特性研究

对Ｃ６０克量级合成与制备获得成功以来的近七、八年间有关溶液中Ｃ６０及其电荷转移配合物（ＣＴＣ）吸光、发光特性研究做了详尽综述。化学特性的改善展示了Ｃ６０及其ＣＴＣ作为新型材料的潜在应用前景。     

Rearrangement of electron density-of-states in magnetic semiconductors

It is shown that in the presence of a strong intratomic correlation the hybridization scattering in magnetic f-semiconductors leads to a cardinal rearrangement of the bare electron spectrum. This arrangement results in the redistribution of electron density into the region far away from the chemical potential and is totally determined by the multi-site scattering processes. The results are compared with the available experimental data on light absorption in europium chalcogenides.     

Reports on progress in polymer physics in Japan

The Calm microbalance system for plasticizer absorption in PVC resin has been used to study the different absorption behaviors of two different plasticizer systems [diisodecyl phthalate (DidP) and a mixed system] on resins of various origins [50-gal reactor and the large reactor pilot plant (LRPP)] and polymerization conditions [different killing pressures (conversion) and two different chemical additives]. The results show that these two chemical additives do not affect the plasticizer capacity of resin but do increase the maximum rate of plasticizer absorption. Killing pressure (conversion) affects both capacity and rate of absorption.     

A quantum pseudodot system with two-dimensional pseudoharmonic oscillator in external magnetic and Aharonov-Bohm fields

Using the Nikiforov–Uvarov (NU) method, the energy levels and the wave functions of an electron confined in a two-dimensional (2D) pseudoharmonic quantum dot are calculated under the influence of temperature and an external magnetic field inside dot and Aharonov–Bohm (AB) field inside a pseudodot. The exact solutions for energy eigenvalues and wave functions are computed as functions of the chemical potential parameters, applied magnetic field strength, AB flux field, magnetic quantum number and temperature. Analytical expression for the light interband absorption coefficient and absorption threshold frequency are found as functions of applied magnetic field and geometrical size of quantum pseudodot. The temperature dependence energy levels for GaAs semiconductor are also calculated.     

Electrodynamic response of a nanosphere placed in a magnetic field

Absorption of electromagnetic radiation by 2D electrons at the surface of a quantum sphere placed in a weak magnetic field is studied. It is shown that at low temperatures, the absorption curve exhibits four resonance peaks observed in the Faraday geometry (photon wave vector parallel to the magnetic field) and six peaks in the Voigt geometry (photon wave vector perpendicular to the magnetic field). In the particular case of the Voigt geometry, where the photon polarization vector is parallel to the magnetic field, the absorption curve exhibits only two resonance peaks. The shape, position, and intensity of the peaks are examined. It is shown that at temperatures close to zero, steps of two types appear in the absorption curve. One type of steps is associated with crossing of the μ-?ω level by the electron energy levels, while steps of the other type arise when electron energy levels cross the chemical potential μ.     

氮作稀释剂DF化学激光器性能评价

对氮作稀释剂DF化学激光器的实用化途径进行探讨,对实验输出性能进行分析研究,并与一般的氦稀释剂DF激光器性能作一比较,结果表明,单从器件本身输出性能来说,氮稀释剂略次于氦稀释剂,但从综合性能考虑,氮稀释剂DF化学激光器仍是实用型器件理想的候选者之一。     

Assessing frequency-dependent site polarisabilities in linear response polarisable embedding

ABSTRACT

In this paper, we discuss the impact of using a frequency-dependent embedding potential in quantum chemical embedding calculations of response properties. We show that the introduction of a frequency-dependent embedding potential leads to further model complications upon solving the central equations defining specific molecular properties. On the other hand, we also show from a numerical point of view that the consequences of using such a frequency-dependent embedding potential is almost negligible. Thus, for the kind of systems and processes studied in this paper the general recommendation is to use frequency-independent embedding potentials since this leads to less complicated model issues. However, larger effects are expected if the absorption bands of the environment are closer to that of the region treated using quantum mechanics.     

马来酰肼多形态的太赫兹光谱研究

分子的多形态(多晶型)是指化学组成相同但存在不止一种晶体形式的物质.这些多形态广泛存在于自然界中,其中药物的多形态尤其普遍.这些药物多形态虽然具有相同的化学分子组成,但其理化性质却存在差异,最终会导致药物作用功能的不同.近年来,随着太赫兹(THz)辐射源的产生方式成为一种常规技术后,太赫兹时域光谱技术(THz-TDS)...     

New working pairs for medium and high temperature industrial absorption heat pumps

The application of absorption cycles for high temperature heat recovery systems calls for the investigation of new working pairs. To qualify as a potential working pair, a mixture of two substances has to fulfill stringent requirements with respect to thermodynamic properties, corrosion and safety hazards like toxicity and inflammability.Based on a thermodynamic analysis of an absorption heat pump cycle a systematic search for new working pairs has been conducted. The investigation dealt exclusively with organic compounds. To get a first estimate of the properties of mixing, a molecular group contribution model (UNIFAC) was employed. This method has so far been widely used for chemical engineering purposes and renders agreeable estimates for the thermodynamic behavior of organic mixtures.With the help of the UNIFAC method, various pairings of functional molecular groups have been investigated for their possible potential to form effective working pairs for medium and high temperature absorption heat pump cycles. As a consequence of this analysis, ten alternative working pairs are proposed and their respective theoretical performance data and their toxicity characteristics are given.     

基于磁激元效应的石墨烯-金属纳米结构近红外吸收研究

石墨烯作为一种单层碳原子二维材料,在可见光和近红外波段吸收率只有2.3%左右,这限制了石墨烯在光电探测、光电调制等领域的应用.本文基于纳米超材料结构的磁激元共振效应,设计了一种金属-绝缘层-金属-石墨烯混合二维浅光栅结构,通过设计混合二维浅光栅结构尺寸来改变石墨烯化学势,实现了石墨烯在近红外波段的吸收增强和调制.利用有限元仿真和等效电路模型,系统地分析了非正入射、结构参数和石墨烯化学势对吸收特性的影响.研究结果表明,混合二维浅光栅结构的磁激元共振效应可以明显提升石墨烯在近红外波段的吸收率,并且对入射角度和极化方向不敏感.在特定结构参数下,混合二维浅光栅结构在1480nm处吸收率达到了85%,其中石墨烯的吸收率为55%,提升了24倍;通过调控石墨烯化学势从0.1eV增大到1.0eV,分别实现了不同结构尺寸下54.8%,50.3%,46.8%的反射率调制深度.     

Ultrasonic absorption in polymer gel dosimeters

Ultrasonic absorption in polymer gel dosimeters was investigated. An ultrasonic interferometer was used to study the frequency (f) dependence of the absorption coefficient (alpha) in a polyacrylamide gel dosimeter (PAG) in the frequency range 5-20 MHz. The frequency dependence of ultrasonic absorption deviated from that of an ideal viscous fluid. The presence of relaxation mechanisms was evidenced by the frequency dependence of alpha/f(2) and the dispersion in ultrasonic velocity. It was concluded that absorption in polymer gel dosimeters is due to a number of relaxation processes which may include polymer-solvent interactions as well as relaxation due to motion of polymer side groups.The dependence of ultrasonic absorption on absorbed dose and formulation was also investigated in polymer gel dosimeters as a function of pH and chemical composition. Changes in dosimeter pH and chemical composition resulted in a variation in ultrasonic dose response curves. The observed dependence on pH was considered to be due to pH induced modifications in the radiation yield while changes in chemical composition resulted in differences in polymerisation kinetics.     

基于FDFD方法研究含石墨烯薄膜太阳能电池的电磁特性

近年来, 基于非晶硅太阳能电池在提高能量转换效率和降低成本等方面的研究越来越受到学者的关注, 其中, 太阳能电池吸收峰值的位置, 反映了电池对该频点及其附近频谱光波吸收具有较好的效果. 然而, 非晶硅太阳能电池的吸收峰位置主要是由非晶硅和金属电极的参数决定, 很难实现位置的可调以及进一步的吸收效率增加. 所以, 在周期结构太阳能电池的金属光栅结构中引入单层石墨烯薄膜, 借助石墨烯的特殊光电特性, 即介电常数可通过改变化学势μ_c来调谐, 并结合频域有限差分方法的数值模拟, 理论上实现了对太阳能电池能量吸收峰位置的调谐. 针对石墨烯电导率的虚部出现奇异点, 本文提出了采用数值拟合予以解决奇异点的方法, 数值结果表明近似表达式的最大绝对误差为0.8%. 本设计结构的理论结果可为实际有机薄膜太阳能电池在工作频段的调节和优化提供理论基础和技术支撑.     

Crossing the gap from p- to n-type doping: nature of the states near the chemical potential in La(2)-(x)Sr(x)CuO(4) and Nd(2-x)Ce(x)CuO(4-delta)

We report on an x-ray absorption and resonant photoemission study on single crystals of the high-T(c) cuprates La2-xSrxCuO4 and Nd(2-x)Ce(x)CuO(4-delta). Using an intrinsic energy reference, we find that the chemical potential of La2-xSrxCuO4 lies near the top of the La2CuO4 valence band whereas in Nd(2-x)Ce(x)CuO(4-delta) it is situated near the bottom of the Nd2CuO4 conduction band. The data clearly establish that the introduction of Ce in Nd2CuO4 results in electrons being doped into the CuO2 planes. We infer that the states closest to the chemical potential have a Cu 3d(10) singlet origin in Nd(2-x)Ce(x)CuO(4-delta) and a 3d(9)L singlet origin in La2-xSrxCuO4.