Raman scattering under extreme conditions

Raman scattering is a versatile and powerful technique and has been widely used in modern scientific research and vast industrial applications. It is one of the fundamental experimental techniques in condensed matter physics, since it can sensitively probe the basic elementary excitations in solids like electron, phonon, magnon, etc. The application of extreme conditions （low temperature, high magnetic field, high pressure, etc.） to Raman scattering, will push its capability up to an unprecedented level, because this enables us to look into new quantum phases driven by extreme conditions, trace the evolution of the excitations and their coupling, and hence uncover the underlying physics. This review contains two topics. In the first part, we will introduce the Raman facility under extreme conditions, belonging to the optical spectroscopy station of Synergetic Extreme Condition User Facilities （SECUF）, with emphasis on the system design and the capability the facility can provide. Then in the second part we will focus on the applications of Raman scattering under extreme conditions to a variety of condensed matter systems such as superconductors, correlated electron systems, charge density waves （CDW） materials, etc. Finally, as a rapidly developing technique, time-resolved Raman scattering will be highlighted here.

Scattering Law Analysis Based on Hapke and Lommel-Seeliger Models for Asteroidal Taxonomy

In deriving the physical properties of asteroids from their photometric data, the scattering law plays an important role, although the shape variations of asteroids result in the main variations in lightcurves. By following the physical behaviors of light reflections, Hapke et al. deduced complex functions to represent the scattering process, however, it is very hard to accurately simulate the surface scattering law in reality. For simplicity, other numerical scattering models are presented for efficiently calculating the physical properties of asteroids, such as the Lommel-Seeliger （LS） model. In this article, these two models are compared numerically. It is found that in some numerical applications the LS model in simple form with four parameters can be exploited to replace the Hapke model in complex form with five parameters. Furthermore, the generated synthetic lightcurves by the Cellinoid shape model also show that the LS model can perform as well as the Hapke model in the inversion process. Finally, by applying the Principal Component Analysis （PCA） technique to the parameters of the LS model, we present an efficient method to classify C and S type asteroids, instead of the conventional method using the parameters of the Hapke model.

Application of neutron scattering in organic photovoltaic materials

Over last decades,the development of new organic materials has contributed to the rapid increase of high-power conversion efficiency of photovoltaic cells.At this stage,to understand the structure and the dynamic of materials is of significant importance for designing novel low-cost photovoltaic cells with superior performance.Neutron scattering is a powerful tool to provide unique and non-destructive information for the organic photovoltaic materials with particular advantages of addressing different parts of organic system by deuterium or tritium substitution.In addition,by employing several neutron scattering methods together,it is possible to further access the static structure and dynamic relaxation of the materials.With this perspective review,we introduce three neutron scattering techniques,including neutron reflectivity,small angle neutron scattering,grazing incidence small angle neutron scattering and quasi-elastic neutron scattering,and their applications on the organic photovoltaic materials.

Kinetics of ring-opening polymerization of octamethylcyclotetrasiloxane in microemulsion

Polysiloxane latexes were prepared by microemulsion polymerization of octamethylcyclotetrasiloxane （D4） in the absence of co-emulsifier with octadecyl trimethyl ammonium chloride as a cationic emulsifier and potassium hydrate as an initiator. The particle size was determined by the dynamic light scattering （DLS） technique and the reaction rates of the polymerization were discussed. Furthermore, the kinetics was studied by an initial-rate method, and the effects of the monomer, emulsifier and initiator concentrations and the temperature on polymerization conversions were investigated. From the kinetic results, the rate of polymerization, Rp at 80℃ can be expressed as Rp = k[D4]^0.79 [OTAC]^0.64[KOH]^0.38 and the aonarent activation energy（Ea）. which was determined by half-period method, is 95.32 kJ mol^-1.