分子激子理论及其在光谱解析中的应用

分子聚集体是通过分子间相互作用形成的,其特殊作用和功能首先在生物体系中得到了人们的认识。分子光谱是聚集态分子研究的有力工具。分子激子理论基于激发态共振相互作用处理分子聚集体,给出了分子聚集体的光谱性质与分子结构之间的关系。本文将对分子激子理论做一简要介绍,并给出分子激子理论在光谱解析中的几个例子。

共轭高聚物双分子链中激子生成的动力学研究

通过对耦合共轭高分子双链中激子生成的动力学研究,讨论了受到光激发后,激子在分子内或分子间生成的制约因素.激子的生成除了受分子链间耦合强度的制约,还受到光激发模式的影响.结果表明,激子既可以在分子内生成,也可以在耦合分子间生成.增大分子之间的相互作用强度,可以增大在分子之间生成激子的概率.

分子二聚体的分子激子理论处理

本文通过对分子二聚体的处理,介绍了一种适于处理弱耦合体系激发态共振相互作用的理论方法——分子激子理论。

聚酰胺-胺树形分子与染料相互作用的分光光度法研究

采用分光光度法对酯端基的半代聚酰胺-胺(PAMAM)树形分子与直接湖蓝5B染料之间的相互作用进行了研究。发现静电相互作用和非极性相互作用同时存在,但静电相互作用起主要作用。半代树形分子导致直接湖蓝5B染料分子采取一定的定向排列,从而引起染料吸收光谱的变化。用分子激子理论对实验现象进行了解释。

Tunneling Electrons Triggered Energy Transfer between Coherently Coupled Donor-Acceptor Molecules

Energy transfer is ubiquitous in natural and artificial lightharvesting systems,and coherent energy transfer,a highly efficient energy transfer process,has been accepted to play a vital role in such systems.However,the energy oscillation of coherent energy transfer is exceedingly difficult to capture because of its evanescence due to the interaction with a thermal environment.Here a microscopic quantum model is used to study the time evolution of electrons triggered energy transfer between coherently coupled donoracceptor molecules in scanning tunneling microscope(STM).A series of topics in the plasmonic nanocavity(PNC)coupled donor-acceptor molecules system are discussed,including resonant and nonresonant coherent energy transfer,dephasing assisted energy transfer,PNC coupling strength dependent energy transfer,Fano resonance of coherently coupled donor-acceptor molecules,and polariton-mediated energy transfer.

Material Growth and Device Fabrication of GaAs Based 1.3μm GaInNAs Quantum Well Laser Diodes

Material growth and device fabrication of the first 1.3μm quantum well （QW） edge emitting laser diodes in China are reported. Through the optimization of the molecular beam epitaxy （MBE） growth conditions and the tuning of the indium and nitrogen composition of the GalnNAs QWs, the emission wavelengths of the QWs can be tuned to 1.3μm. Ridge geometry waveguide laser diodes are fabricated. The lasing wavelength is 1.3μm under continuous current injection at room temperature with threshold current of 1kA/cm^2 for the laser diode structures with the cleaved facet mirrors. The output light power over 30mW is obtained.

Smaller Ge Quantum Dots Obtained by ArF Excimer Laser Annealing

Ge self-assembled quantum dots （SAQDs） are grown with a self-assembled UHV/CVD epitaxy system. Then, the as-grown Ge quantum dots are annealed by ArF excimer laser. In the ultra-shot laser pulse duration, -20ns, bulk diffusion is forbidden,and only surface diffusion occurs, resulting in a laser induced quantum dot （LIQD）. The diameter of the LIQD is 20-25nm which is much smaller than the as-grown dot and the LIQD has a higher density of about 6 ×10^10cm^-2. The surface morphology evolution is investigated by AFM.

Highly-Strained InGaAs/GaAs Single-Quantum-Well Lasers Grown by Molecular Beam Epitaxy

Highly stained InGaAs/GaAs Quantum Wells (QW) are grown by using molecular beam epitaxy.The room-temperature photoluminescence (PL) peak wavelength as long as 1160nm is obtained from QW with the In composition of 38% and the well width of 6 8nm.The full-width at half-maximum of the PL peak is 22meV,indicating a good quality.InGaAs/GaAs QW ridge-waveguide lasers with emission wavelength of 1120nm are demonstrated.For 100-μm-wide ridge-waveguide lasers with a cavity length of 800μm,the kink-free output power up to 200mW is achieved with the slope efficiency of 0 84mW/mA under the continue-wave operation.For 10μm-wide ridge-waveguide lasers,the lowest threshold current density of 450A/cm2 and the characteristic temperature of 90K are obtained.

Temperature Dependence of Vacuum Rabi Splitting in a Single Quantum Dot-Semiconductor Microcavity

The quantum dynamics of an exciton dressed by acoustic pnonons in an optically driven quantum dotsemiconductor microcavity at finite temperatures is investigated theoretically by quantum optics methods. It is shown that the temperature dependence of the vacuum Rabi splitting is 2√2g×exp[ - ∑qλq（Nq＋1/2）],where Nq=1/[exp（ωq/kBT）-1] is the phonon population, g is the single-photon Rabi frequency, and λq corresponds to exciton-phonon coupling.

Raman and Infrared Spectra for All-trans-astaxanthin in Dimethyl Sulfoxide Solvent

The Raman and infrared spectra of all-trans-astaxanthin （AXT） in dimethyl sulfoxide （DMSO） solvent were investigated experimentally and theoretically. Density functional cal-culations of the Raman spectra predict the splitting of the υ1 band into υ1-1 and υ1-2 compo-nents. The absence of splitting in Raman experimental spectra is ascribed to the competition between the two symmetric C=C stretching vibrations of the backbone chain. The υ1 band is very sensitive to the excitation wavelength： resonance excitation stimulates the higher-frequency υ1-2 mode, and off-resonance excitation corresponds to the lower-frequency υ1-1 mode. Analyses of the intramolecular hydrogen bonding between C=O and O-H in the AXT/DMSO system reveal that the C4=O1...H1-O3 and C4＇=O2...H2-O4 bonds are strengthened and weakened, respectively, in the electronically excited state compared with those in the ground state. This result reveals significant variations of the AXT molecular structure in different electronic states.

Efficient Preparation of D2 Molecules in v=2 by Stimulated Raman Pumping

We report the preparation of D2 molecules in v=2 level in molecular beam condition. A single longitudinal mode laser system was used for excitation of D2 from （v=0, j=0） to （v=2, j=0） with the scheme of stimulated Raman pumping. An excitation efficiency of 25.2% has been achieved, which was determined by the scheme of resonance-enhanced multiphoton ion- ization. Dependence of relative excitation efficiency on laser energy has been measured. We found that the increasing rate of excitation efficiency became slower as pulse energy of Stokes laser increase, while the excitation efficiency still increases approximately linearly with pump pulse energies up to 60 mJ. The spectral line shapes of Raman transition was also measured at different laser energies and considerable dynamical Stark effect was observed. A single peak was found on the three dimension surface of relative excitation efficiency, indicating the process occurred in the present study is a process of stimulated Raman pumping instead of stimulated adiabatic Raman passage.

Molecular oxygen activation enhancement by BiOBr0.5I0.5/BiOI utilizing the synergistic effect of solid solution and heterojunctions for photocatalytic NO removal

To improve the photocatalytic oxidation reaction activity for NO removal, photocatalysts with excellent activity are required to activate molecular oxygen. Solid solution and heterojunction were suggested as effective strategies to enhance the molecular oxygen activation viaexciton and carrier photocatalysis. In this study, a solid solution and heterojunction containing BiOBr0.5I0.5/BiOI catalyst was synthesized, and it showed improved photocatalytic activity for removing NO. The photocatalytic NO removal mechanism indicated that synergistic effects between the solid solution and heterojunction induced the enhanced activity for molecular oxygen activation. The photogenerated holes, superoxide, and singlet oxygen generated by the carrier and exciton photocatalysis supported the high photocatalytic NO removal efficiency. This study provides new ideas for designing efficient Bi-O-X(X = Cl, Br, I) photocatalysts for oxidation reactions.

Room Temperature Operation of Strain-Compensated 5.5μm Quantum Cascade Lasers

Room temperature operation is an important criterion for high performance of quantum cascade lasers. A strain-compensated quantum cascade laser（λ≈5.5μm） with optimized waveguide structure lasing at room temperature is reported. Accurate control of layer thickness and strain-compensated material composition is demonstrated using X-ray diffraction. An output power of at least 45mW per facet is realized for a 20μm-wide and 2mm-long laser at room temperature.

Investigation on Exciton Relaxation Kinetics of ZnCulnS/ZnSe/ZnS Quantum Dots by Time-Resolved Spectroscopy Techniques

The exciton relaxation kinetics of ZnCuInS/ZnSe/ZnS quantum dots （QDs） is investigated by time-resolved spectroscopy techniques in detail. Based on the rate distribution model, the wavelength-dependent emission dynamics shows that the intrinsic exciton, the exciton in the interface defect state and that in donor-acceptor pair state （DAPS） together participate in the photoluminescence process of QDs, and the whole emission process is mainly dependent on the DAPS emission. Transient absorption data show that the intrinsic exciton and the interface defect species maybe together appear after excitation and the intensity-dependent Auger recombination process also exists in QDs at high excitation intensity.

Experimental and Theoretical Investigation on Excited State Intramolecular Proton Transfer Coupled Charge Transfer Reaction of Baicalein

The excited state intramolecular proton transfer （ESIPT） coupled charge transfer of baicalein has been investigated using steady-state spectroscopic experiment and quantum chemistry calculations. The absence of the absorption peak from S1 excited state both in the experi-mental and calculated absorption spectra indicates that S1 is a dark state. The dark excited state S1 results in the very weak fluorescence of solid baicalein in the experiment. The fron- tier molecular orbital and the charge difference densities of baicalein show clearly that the S1 state is a charge-transfer state whereas the S2 state is a locally excited state. The only one stationary point on the potential energy profile of excited state suggests that the ESIPT reaction of baicalein is a barrierless process.

STUDY ON OCCURENCE FORM OF PLATINUM IN XINJIE Cu－Pt DEPOSIT BY NAA AND SCANNING PROTON MICROPROBE

A combination of NAA and micro-PIXE was used to study concentrations and distributions of platinum group elements (PGE) in ores from Xinjie Cu-Pt deposit.The NAA results of the bulk indicate that the ores belong to the enriched Pt-Pd type.The element concentration maps of scanning micro-PIXE for the ores show that the occurence form of Pt is independent arsenide minerals. No PGE were detected in chalcopyrite of Xinjie Cu-Pt deposit. These information are economically beneficial to the mineral smelting process.

Functional Integrals and Collective Excitations in Boson-Fermion Model

In this paper, collective excitations in the boson-fermion model are investigated by means of functional integration method. The equations of energy gap and excitation spectrum are derived. Moreover, the Bose energy spectrum of zero wave vector Fermi fields is also calculated.

Laser Ablation Atomic Beam Apparatus with Time-Sliced Velocity Map Imaging for Studying State-to-State Metal Reaction Dynamics

We report a newly constructed laser ablation crossed molecular beam apparatus, equipped with time-sliced velocity map imaging technique, to study state-to-state metal atom reaction dynamics. Supersonic metal atomic beam is generated by laser vaporization of metal rod, and free expansion design without gas flow channel has been employed to obtain a good quality of metal atomic beam. We have chosen the crossed-beam reaction Al＋O2 to test the performance of the new apparatus. Two-rotational-states selected AIO（X^2∑＋, v=0, N and N＋I4） products can be imaged via P（N） and R（N＋14） branches of the Av=l band at the same wavelength, during （1＋1） resonance-enhanced multi-photon ionization through the AIO（D2E＋） intermediate state. In our experiment at 244.145 nm for simultaneous transitions of P（15） and R（29） branch, two rings in slice image were clearly distinguishable, corresponding to the AiO（v=0, N=IS） and AIO（v=0, N=29） states respectively. The energy difference between the two rotational levels is 403 cm^-1. The success of two states resolved in our apparatus suggests a better collisional energy resolution compared with the recent research study [J. Chem. Phys. 140, 214304 （2014）].

Treatment for triple-negative breast cancer

Triple-negative breast cancers (TNBCs) neither express estrogen receptor and progesterone receptor nor over- express human epidermal growth factor receptor-2. Because of the special molecular features, triple-negative breast cancer is not either sensitive to endocrine therapy or targeted therapy of trastuzumab. There has not been standard treatment regimen for triple-negative breast cancer yet and chemotherapy has still been the chief therapy currently. However, with the great progress of oncology and molecular biology, the understanding of the natural history, pathophysiology and molecular features of this disease has been greatly improved, and a growing number of novel and effective therapies and discoveries of new biological targets for this phenotype of breast cancers have been reported, which provide new insights into therapeutic strategies for the women suffering from it.

Ion-Pair Dissociations of Br CN by Electron Impacts

Ion-pair dissociation is an important molecular process and frequently happens when the target molecule is pumped to its electronically superexcited states. In contrast to the experimental studies of photoexcitation ion-pair dissociation, there are some experimental challenges in the electron-impact ion-pair dissociation study, in particular, on determination of the energetic threshold. Here we report an experimental development for the ion-pair dissociation study by using the monochromized electron impacts. As an example, the threshold of BrCN→Br^-+CN^+ is determined as 13.78 eV according to the appearance energy of CN^+ signals, meanwhile, the time-sliced ion velocity image of CN^+ is recorded at 16.09 eV and indicates an anisotropic distribution of the CN^+ momentum.