Structure and Morphology of a Polyether/Polyacrylate Semi-interpenetrating Polymer Network

In this study NMR and DSC are used to probe the structure, thermal characteristics and morphology of a network formed from a diepoxide/acrylate system. Separate chemistries are employed to polymerize the diepoxide and acrylate components. The cationic polymerization of the diepoxide exhibits excellent selectivity in producing a crosslinked polyether network without affecting the acrylate monomer. Subsequent photoinitiated free-radical polymerization of the acrylate produces a phase separated, semi-interpenetrating polymer network (SIPN).This revised version was published online in November 2005 with corrections to the Cover Date.     

Nondegenerate plasma with a diffusive boundary condition in a high-frequency electric field near resonance

An analytical solution of the linearized problem concerning the behavior of collisional non-degenerate plasma in an external electric field is obtained. It is assumed that the electrons are diffusively scattered from the plasma boundary. The resulting solution is used to determine the screening field. The case of a high-frequency external field with a frequency close to the plasma resonance frequency is examined.     

Resonance ionization mass spectrometry for precise measurements of isotope ratios

Resonance ionization mass spectrometry offers extremely high sensitivity and elemental selectivity in microanalysis, but the isotopic precision attainable by this technique has been limited. Measured isotope ratios are sensitive to small fluctuations in the pointing, pulse timing, and wavelength of the resonance lasers. We show that, by minimizing these fluctuations using feedback controls and by power-broadening the optical transitions, we are able to measure chromium isotope ratios with statistics-limited precision better than 1%. Small additional improvements in reproducibility come from careful shaping of the electric field in the region where atoms are photoionized and from minimizing pulse-to-pulse variations in the time-of-flight mass spectrometer through which the photoions travel. The increased reproducibility of isotopic measurements on standard materials has enabled us to detect anomalous chromium isotopic abundances in presolar SiC grains extracted from primitive meteorites.     

Calculation of light emission in sonoluminescence

We modify a uniform model of single bubble sonoluminescence, in which heat diffusion, water vapor diffusion and chemical reactions are included to describe the bubble dynamics, and the processes of electron-atom bremsstrahlung, electron-ion bremsstrahlung and recombination radiation, radiative attachment of electrons to atoms and molecules, line emissions of OH radicals and Na atoms are taken into account to calculate the light emission. With this model, we compute the light pulse width, the photon number per flash, the continuum and line spectra and the gas species as the products of chemical reactions, and try to compare with all the experimental data available. We obtain good agreement with the observations of Ar and Xe bubbles in many cases, but fail to match the experimental data of the photon number per flash. We also find that for He bubble the computed photon number is always too small to interpret the observations. Supported by the National Natural Science Foundation of China (Grant Nos. 10674081 and 10434070)     

Ne^3P0,2）与乙腈的能量转移反应研究

在流动余辉装置上，我们研究了亚稳态原子Ｎｅ（＾３Ｐ０，２）与乙腈的能量转移反应，观察到了ＣＮ（Ａ－Ｘ），ＣＮ（Ｂ－Ｘ），ＣＨ（Ａ－Ｘ）的发射谱。计算了ＣＮ（Ａ，Ｂ）的相对振动粒子数布居，并对该反的机理进行了讨论。     

Plasma in a high-frequency electric field with a reflective condition on the boundary

An analytical solution is obtained for the linearized problem of the behavior of a collisional gas plasma in a half-space in an external alternating electric field. It is assumed that the electrons are mirror-reflected from the plasma boundary. The solution is used for finding the screened field. The case of an external field frequency close to the plasma frequency is investigated separately.