掺杂ZnSe/BeTe Ⅱ型量子阱结构中带电激子的磁场效应

报道了n型掺杂ZnSe/BeTe/ZnSe Ⅱ型量子阱(type-Ⅱ QW)在极低温 (5—10 K)条件下的各种光学性质. 磁场中(Farada配置)ZnSe层的反射光谱展示了一个典型的负的带电激子(X^-)的跃迁特征. 对于空间间接光致发光(spacially indirect PL)光谱,它的主发光峰显示了一个反玻尔兹曼分布的非对称性,并且在磁场中(Voigt配置)它的峰值能量随磁场的增加而降低. 这些实验结果显示了该掺杂样品的空间间接PL是来自Ⅱ型QW结构所特有的带电激子的跃迁. 关键词： 光致发光 二维电子气 带电激子 Ⅱ型量子阱     

Angular dependence of electronically allowed nuclear bragg reflection of Mössbauer radiation

A typical angular integrated Mössbauer reflection spectrum of an electronically allowed nuclear Bragg reflection was analysed. Mössbauer reflection spectra were measured with high angular resolution. They reveal almost pure nuclear scattering far off Bragg and strong nuclear-electronic interference in the scattering near and at Bragg. The spectra show a pronounced asymmetry with respect to the Bragg position, which is caused by refraction and by interference of nuclear and electronic scattering.     

人膀胱粘膜/粘膜下层组织病变致组织漫反射光谱的变化

研究了人正常膀胱和浅表性膀胱癌的粘膜/粘膜下层组织在300～900nm光谱范围的漫反射光谱特性及其差异,实验采用带积分球附件的分光光度计获取组织的漫反射光谱.结果表明,在300～900 nm,正常膀胱的粘膜/粘膜下层对任一个波长的漫反射率都明显地较癌变的粘膜/粘膜下层对相应波长的要大.正常膀胱的粘膜/粘膜下层的漫反射光谱的峰分别在370 nm、520 nm、550 nm和660nm,其峰值分别为52.4%、60.7%、56.1%和75.5%.而癌变的粘膜/粘膜下层的漫反射光谱的峰分别在320 nm、520 nm、550 nm和660 nm,其峰值分别为43.7%、33.4%、30.6%和70.2%.正常膀胱的粘膜/粘膜下层的漫反射光谱在370 nm处有一个峰,而癌变的粘膜/粘膜下层的漫反射光谱在370 nm处没有峰,320 nm处有一个峰.而正常膀胱的粘膜/粘膜下层的漫反射光谱在320 nm处没有峰.膀胱的粘膜/粘膜下层病变导致组织的漫反射光谱在520 nm、550 nm和660 nm处的峰的峰值分别减小了45.0%、45.5%和7.02%.说明膀胱的粘膜/粘膜下层病变导致组织的组分和结构尤其足组织中的氧合血红蛋白和去氧血红蛋白的含量发生了明显的改变.     

A method for removing etalon oscillations from THz time-domain spectra

We present a simple algorithm for removing or reducing spurious oscillations in the THz spectra which result from secondary reflection peaks in samples or optical elements. The algorithm utilizes the fact that a THz time-domain trace containing secondary peaks can be represented as a convolution of the primary peak and two or more delta functions. The algorithm is applicable for samples which are sufficiently thick that the reflection peak does not overlap with the primary peak, and that do not have strong absorption or dispersion.     

Chiral photonic crystals with an anisotropic defect layer: Oblique incidence

In the present paper we consider some properties of defect modes in chiral photonic crystals with an anisotropic defect layer at oblique light incidence. The problem is solved by Ambartsumian’s layer addition method. We investigated some peculiarities of the discussed system’s reflection spectra of the oblique light incidence for both the minimum and essential influences of the dielectric boundaries. Then we investigated some particulars of the density of photonic states spectra. We also discussed some peculiarities of the light energy distribution in the system. We found out that at large incidence angles two defect modes arise in the two regions of the selective reflection, each in one respectively, meanwhile, none arises in the central region of the complete reflection. Our investigations show that it is possible to rather widely change the emission peak wavelength in the subject system doped with some laser dye, by changing the incidence angle.     

Thermoreflectance study of direct and indirect excitons near the fundamental edge of GaSe

Thermoreflectance spectra have been obtained on GaSe single crystals between 50 and 300 K and a theoretical model is developed to fit the experimental curves. The main feature of the spectra is due to the disappearance of the back reflection of the sample caused by the small absorption below the direct exciton. The direct excitonic structure is observed at higher energy.     

Fabrication of 2D–3D photonic crystal heterostructures by glancing angle deposition

We fabricate 2D–3D photonic crystal heterostructures based on the silicon [001]-diamond:1 square spiral geometry using glancing angle deposition. We compare the normal incidence reflection properties of the fabricated 2D–3D heterostructures to simulated spectra generated using finite-difference time-domain calculations. Reflection peaks are observed, resulting from the presence of a photonic band gap, and defect modes are created by the 2D layer. Deterioration of the reflectance peaks with increased number of vertical spiral periods is observed. A series of square spiral structures are fabricated with a varying number of vertical periods to quantify the degradation of reflection peaks. At normal light incidence, a maximum reflection peak is observed from the film with three vertical periods. Beyond three spiral rotations, deterioration of the substrate-plane periodicity causes scattering losses.     

Temperature dependence of phonon energy spectra with nuclear resonant scattering of synchrotron radiation

Summary The phonon energy spectra of a polycrystalline α-Fe foil were observed at 150 K and 300 K by using the nuclear resonant scattering of synchrotron radiation. In each spectrum, inelastic scattering was observed at both sides of the elastic peak. It was found that the ratio of the elastic-scattering component and the asymmetry of the intensity of the side bands observed at 150 K are larger than those observed at 300 K, respectively. The observed temperature-dependent spectra are in good agreement with the spectra calculated from the phonon energy distribution function. One of the advantageous features of this method is that the excitation of only a specific element is possible. Our results show that this method is applicable to the study of lattice dynamics and opens a new field of the nuclear resonant scattering spectroscopy. Paper presented at ICAME-95, Rimini, 10–16 September 1995.     

常见灰色珍珠的紫外可见漫反射光谱类型及其灰色成因

基于紫外可见（UV-Vis）漫反射光谱就当前市售流通领域常见的灰色珍珠品类进行表征并依据样品的反射谱图的类同特征予以分类,并初步探究了灰色珍珠的颜色成因。研究表明：(1)基于灰色珍珠的UV-Vis 漫反射光谱中约280 nm 处吸收峰的有无,首次将灰色珍珠分为Ⅰ型（存在明显的吸收）与Ⅱ型（无吸收或仅存在较弱的吸收）。并据Ⅰ型珍珠在其紫外可见光区的反射峰形与其反射主波长位置的差异进一步分为Ⅰn, Ⅰp与Ⅰf三个亚型,上述Ⅰ型珍珠均为有核珍珠。其中Ⅰp型珍珠的内核为白色、内核与珍珠层之间较多存在褐色、黑褐色的过渡层,该过渡层可能是导致珍珠呈灰色的直接原因。与此同时,上述Ⅰp型珍珠在宝玉石鉴定领域一般认为是未经处理的。（2）结合前人就珍珠辐照的相关工作及本工作中贝壳珍珠层辐照前后颜色的改变及UV-Vis反射光谱的变化特征, 推断辐照仍是人工处理导致珍珠呈现灰色主要原因之一。基于样品对应的UV-Vis反射光谱中约280 nm吸收峰的消失或仅呈现一吸收肩可初步定性该类珍珠经优化处理。同时,从Ⅱ类灰色珍珠的断面结构看,当前灰色珍珠并不仅局限于有核珍珠,无核灰色珍珠同样存在于流通领域。课题研究工作可为灰色珍珠及其优化处理品的鉴定提供理论与技术支撑。     

不同处理工艺对珍珠的紫外可见漫反射光谱的共性影响研究

主要基于紫外可见（UV-Vis）漫反射光谱首次对比研究了经过热处理、有机或无机染料改色或钴-60产生的γ射线辐照三种不同处理工艺对同为珍珠质的淡水与海水珍珠及贝壳珍珠层的漫反射光谱的影响机制。结果表明：（1）在不同颜色、淡海水属性的珍珠与贝壳珍珠层的UV-Vis反射光谱的紫外区皆存在约280 nm 处的吸收峰,上述吸收峰位归属于珍珠层中自身存在的有机质所致,而非珍珠的致色色素。（2）以上三种不同的处理工艺对上述280 nm处的吸收峰位存在一致的影响行为,即随着不同的处理工艺强度的增大,处理样品对应的反射谱图中约280 nm处吸收峰的强度逐渐降低直至消失。与此同时,珍珠的反射谱图中紫外区的反射主波长的反射强度也随之减弱,且反射主波长的峰位向可见光区发生显著红移。研究工作可为珍珠及珍珠的优化处理的鉴定筛选及其珍珠颜色的形成属性判定提供检测依据与理论支撑。     

Reflection spectra of orthorhombic indium iodide

The reflection spectra of InI single crystal have been measured using linearly polarized light. Pronounced anisotropy is observed between two directions of polarization E ∥ c and E ∥ a. The first peak at 2.018 eV for E ∥ c is direct allowed exciton transition with binding energy 4.3 meV. The E ∥ a spectrum suggests that the transition is forbidden.     

Differential birefringence in Bragg gratings in multicore fiber under transverse stress

We present experimental measurements of the peak splitting of the reflection spectra of fiber Bragg gratings as a result of birefringence induced by transverse loading of a multicore fiber. Measurements show that the splitting is a function of the applied load and the direction of the load relative to the azimuth of the fiber. A model for calculating the stress in the fiber that is due to an applied load is in good agreement with our experimental observations.     

Global calculations of ground-state axial shape asymmetry of nuclei

Important insight into the symmetry properties of the nuclear ground-state (gs) shape is obtained from the characteristics of low-lying collective energy-level spectra. In the 1950s, experimental and theoretical studies showed that in the gs many nuclei are spheroidal in shape rather than spherical. Later, a hexadecapole component of the gs shape was identified. In the 1970-1995 time frame, a consensus that reflection symmetry of the gs shape was broken for some nuclei emerged. Here we present the first calculation across the nuclear chart of axial symmetry breaking in the nuclear gs. We show that we fulfill a necessary condition: Where we calculate axial symmetry breaking, characteristic gamma bands are observed experimentally. Moreover, we find that, for those nuclei where axial asymmetry is found, a systematic deviation between calculated and measured masses is removed.     

硼掺杂单壁碳纳米管吸附甲醛的电子结构和光学性能研究

应用基于第一性原理的密度泛函理论研究了硼原子取代掺杂的（8,0）碳纳米管吸附甲醛气体分子的束缚能、电子结构以及光吸收和反射性质.研究发现,硼原子掺杂的碳纳米管对甲醛气体具有较强的敏感性,其束缚能大大增加,电荷转移更加显著,吸收峰和反射峰增多,峰值减小,且在低能区发生蓝移现象,在能量约为172 eV处均出现一特征峰.对计算结果进行了讨论,期望利用硼掺杂碳管来制作检测甲醛的纳米传感器和光电器件. 关键词： 碳纳米管 甲醛 硼原子取代掺杂 光学性能     

ZnO薄膜光学常数测量

利用Kramers-Kronig方法(K-K方法)测量了ZnO薄膜的复介电常数和复折射率(折射率和消光系数)。为了满足K-K方法所要求的条件,光源发出的光束通过一个特殊设计的中间带孔的反射镜垂直投射到ZnO薄膜表面,在ZnO薄膜表面产生的反射光穿过反射镜中间的小孔进入单色仪,从而测量出正入射情况下ZnO薄膜的反射光谱。对有限波段下测量的数据经合理的外推后,得出全波段的薄膜反射谱,然后利用K-K方法计算出ZnO薄膜的复介电常数和复折射率。实验结果表明,氧化锌薄膜在可见光范围内的折射率近似为一常数3．5;在430nm附近出现折射率最大值,而在短波长范围所对应的折射率大大降低,其值在0．5—2．5之间起伏波动。     

Nondipole Effects in Atomic Ionization Induced by an Intense Counter-Rotating Bicircular Laser Field

Nondipole effects occurring in the process of atomic ionization by an intense, mid-infrared, counter-rotating bicircular laser field are investigated using the strong-field approximation with leading-order nondipole corrections. The time integrals appearing in the expression for the differential ionization rate are computed in two ways: numerically, and by applying the saddle-point approximation. The nondipole corrections introduce an asymmetry in the photoelectron momentum distribution along the field propagation direction. The asymmetry is quantified by the partial average value of the propagation-direction momentum component of the photoelectrons and by the normalized difference of the differential ionization rates computed including and excluding the nondipole corrections. Using the saddle-point approximation, it is investigated how the nondipole corrections change the solutions for direct photoelectrons and how this affects the momentum spectra. The impact of nondipole corrections increases with increasing photoelectron energy. Analysis of the complete photoelectron spectra including both direct and rescattered photoelectrons shows that, in the low-energy region, a shift against the propagation direction occurs. The partial average of the propagation–direction momentum component in the rescattering region exhibits a plateau structure and also a local minimum structure that was recently observed in an experiment with a linearly polarized laser field (Lin et al., Phys Rev. Lett. 128, 023201 (2022)).     

Studies on 2,4-DNT Mixtures Using Reflection Terahertz Time Domain Spectroscopy for Explosives Detection

Absorption spectra （0.2-1.8 THz） of the mixtures of explosive 2,4-DNT and polyethylene（PE） at different ratios are obtained using reflection terahertz time domain spectroscopy （THz-TDS）. The pronounced absorption peak of 2,4-DNT at 1.08 THz is always observed for the mixtures with 2,4-DNT ratios above 20%. Experimental results demonstrate that more applicable and realistic THz-TDS in reflection geometry can be used to distinguish explosive mixed with other material having no THz fingerprints, and has a high potential in the detection of explosives.     

Ce3+,Mn2+激活氟磷酸钙的发光中心及其相互作用

研究了Ce3+,Mn2+激活的氟磷酸钙(FAP:Ce3+,Mn2+)的发光光谱、激发光谱、漫反射光谱、发光衰减以及顺磁共振谱,首次发现了FAP:Ce3+,Mn2+中Ce3+可以形成两种发光中心;同时也发现在该材料中Mn3+的发光中心与普通卤粉相似,即存在MnⅠ和MnⅡ两种中心;研究表明,由Ce3+中心向Mn2+中心的能量传递具有相当高的效率,传递机制属偶极子-偶极子相互作用;在Ce3+→Mn2+能量传递过程中,MnⅠ中心优先被Ce3+中心敏化。     

Study of the parameters of the He(3 <Superscript>3</Superscript>S)-He(2 <Superscript>3</Superscript>P) line *

We have observed emission spectrum in dense plasmas of helium excited by a corona discharge at 706.69 nm. In continuation of an analysis of spectra obtained in gaseous helium at 300 K, we report on a study of the line parameters of the observed spectra. We discuss the major importance of temperature and perturber density in the broadening, shift and asymmetry measured from calculated profiles within a unified line shape semi-classical theory. The comparison is done with existing data derived from experimental spectra at 300 K. The theoretical work is extended at lower temperatures down to 40 K.     

Site equivalent all Apex 1 nm-particle of CdSe preferentially grown in solution

A 1-nm particle of CdSe showing a sharp photoabsorption peak at 350 nm has been selectively synthesized as a single species in solution. Solid NMR spectra of both atoms show a single narrow peak of large chemical shift anisotropy and asymmetry compared with the essentially isotropic bulk CdSe. This result indicates that this extremely small 1-nm particle has most of its atoms at the surface, and the atoms are deformed from the sp³ configuration of the bulk fragment into an assembly consisting entirely of apexes of equivalent symmetry that are particularly stable and preferentially grown. This observed selective stability presents the possibility of growing 1-nm particles with an atomic monostructure in macroscopic quantities.