Electron-photon coincidence studies on electron impact excitation of lighter neutral atoms

Recently we applied non-relativistic distorted wave approximation theory to study electron impact excitations in lighter atoms (viz. hydrogen, helium and some alkalis). Excitations from the ground and (or) initially excited metastableS states to next upper excitedP andD states have been considered. Results for the differential cross-sections and electron-photon coincidence parameters are obtained. Here the theory and the calculation of various scattering parameters are described briefly and some selected results are presented and discussed.     

Spectroscopic properties of ZnWO4 single crystal doped with Fe and Li impurities

The influence of Fe and Li co-doping on optical properties of ZnWO₄ crystals have been investigated by optical spectroscopy and electron paramagnetic resonance (EPR). The iron ions were added to the ZnWO₄ composition in the form of Fe⁰, FeO or Fe₂O₃. EPR has been used for determination of the Fe³⁺ concentration. The luminescence and excitation spectra obtained at different temperatures are presented. Under excitation 325 nm, two bands were observed: blue-green emission peaked at 490 nm and red peaked at 650 nm. The blue- green emission is related to Fe³⁺ and their shape depends on the doping method. The red emission is not related to the Fe³⁺.     

The Analysis of the Spurious Field about HL-2A Tokamak

To better the shielding of outer magnetic field when making the experiment on neutral particle measurement and neutral beam injection outside of HL-2A, it would be necessary to determine the distribution of outer magnetic field, which the excitation coils inducet. This experiment is done to measure and analyze the spurious field.     

Electric properties of the water molecule in 1A1, 1B1, and 3B1 electronic states: Refined CASSCF and CASPT2 calculations

Summary The dipole moments and dipole polarizabilities of the ¹A₁, ¹B₁, and ³B₁ electronic states of the water molecule have been calculated by using the CASSCF approach followed by the evaluation of the dynamic electron correlation contribution by the second-order perturbation scheme CASPT2. All calculations have been carried out in a specifically extended ANO basis set which accounts for the Rydberg character of the two excited states. In order to estimate the correctness and accuracy of the present data a scan over a variety of different active spaces for the CASSCF wave function has been made. The present results are superior to earlier CASSCF calculations, although their qualitative features remain essentially the same. The dipole moments in ¹B₁ and ³B₁ states are predicted to be about 0.49 a.u. and 0.33 a.u., respectively, and have the opposite orientation with respect to the ground state dipole moment. The dipole polarizability tensors of the excited states are characterized by high anisotropy and are dominated by the in-plane component perpendicular to the symmetry axis. All their components are found to be about an order of magnitude larger than those of the ground state polarizability tensor. The excitation energy dependence on the choice of the active orbital space in the CASSCF reference function is also considered and the analysis of the present data concludes in the concept of what is called the mutually compatible active spaces for the two states involved in excitation. All CASPT2 results are in good agreement with the results of recent calculations carried out in the framework of the open-shell coupled cluster formalism. This agreement confirms the high efficiency of the CASSCF/CASPT2 approach to the treatment of the electron correlation effects.     

Synthesis and luminescence properties of nanocrystalline YVO4:Eu

Nanocrystalline YVO₄:Eu³⁺ was synthesized by direct precipitation reaction, which was then annealed at different temperatures. The results of XRD showed that nanocrystalline YVO₄:Eu³⁺ could be obtained in solution at 60 °C, and the mean particle sizes of samples are increased as annealing temperature is increased. The results of TEM exhibit that the sizes of samples are around 5-30 nm. Studies on the excitation spectra show that there are a large number of the structural distortions in smaller particles. By analyzing line splitting patterns and peaks broadening in the emission spectra, we consider that the deviations in intensity patterns of ⁵D₀-⁷F₂ are affected by distortions of crystal lattice. Some abnormal behaviors can be attributed to higher ratio of surface to volume, which lead to the different local symmetry environment of Eu³⁺ ions on the surface.     

Calculation of vertical excitation energies of closed-shell molecules in the CNDO and INDO approximations

The Green's function method for the calculation of vertical excitation energies is adapted to the CNDO and INDO approximations by introducing an effective interaction into the irreducible vertex part. The computational scheme is explicitly developed for closed-shell molecules and applied to H₂O, H₂CO, HCOOH, HCONH₂.     

基于共轭聚合物的纳米粒子用于肿瘤的近红外二区荧光成像及光热治疗

为提高生物组织荧光成像质量以及对肿瘤的高效光热治疗,设计合成了一种新型的窄带隙共轭聚合物(BDT-TTQ),并通过纳米沉积的方式将聚合物制备成水溶性纳米粒子(BDT-TTQ NPs).该共轭聚合物纳米粒子在1000~1200 nm近红外二区范围具有较好的吸收,在1064 nm的激发光下能实现1200~1400 nm的近红外二区荧光成像. BDT-TTQ NPs纳米粒子粒径分布较窄,形貌呈规则的球形且分散均匀,具有好的生物相容性.该纳米粒子既可以在体外实现较高的近红外二区荧光成像穿透深度,又可以实现对小鼠活体血管的高清晰度的近红外二区荧光成像.此外,BDT-TTQ NPs纳米粒子在1064 nm激光下展现出优异的光热转换效率,具有较高的光毒性,对体外的肿瘤细胞以及小鼠的异质瘤具有高的光热杀伤能力.     

Liquid State Relaxation Processes of Electronically Excited Luminophors Detected by Time-Resolved Spectroscopy and Travelling Wave Dye Lasers

Experimental findings concerning liquid state relaxation processes of electronically excited molecules, coming from time-resolved spectroscopy and travelling wave dye lasers, offer a formidable basis for restructuring some of the theories dealing with relaxation processes. Comparison of the prime research literature with standard texts shows a severe time lag in the dissemination of essential concepts, while comparison of ‘traditional’ fluorescence with intra-cavity photon emission reveals basic differences involving relativistic effects and vector space construction, mitigating against the practice of directly incorporating laser based data into ordinary chemical dynamics.     

Quantitative analysis of UV excitation bands for red emissions in Pr-doped CaTiO3, SrTiO3 and BaTiO3 phosphors by peak fitting

A quantitative spectral analysis of the ultraviolet (UV) broad excitation bands, which are located in the range 300-400 nm, for red emissions at around 610 nm in Pr-doped CaTiO₃, SrTiO₃:Al and BaTiO₃:Mg phosphors has been carried out using a peak fitting technique. The obtained results demonstrate that the UV broad band of CaTiO₃:Pr consists of four primary excitation bands centered around 330, 335, 365 and 380 nm and those of both SrTiO₃:Al and BaTiO₃:Mg consist of three primary bands centered around 310, 345 and 370 nm. Based on the behavior patterns and the values of the respective primary excitation bands’ parameters, i.e. center gravity (λ_top), maximum height (I_max) and full-width at half-maximum (FWHM), the UV-to-red relaxation processes in these titanate phosphors can be explained to be essentially the same, except for the existence of an additional relaxation pathway via electron-trap states in CaTiO₃:Pr, which gives a characteristic shape of its UV excitation spectrum in the wavelength range of >360 nm.