激光冷却和捕陷中性原子③

6 激光冷却和捕陷中性原子技术的应用 前面已经提到,激光冷却和捕获中性原子技术最主要的应用是在精密计量和超冷原子物理两个方面.在精密计量方面最为典型的是可用于原子频标的"原子喷泉"(atomic fountain)技术;而在超冷原子物理方面最为典型的是玻色-爱因斯坦凝聚(Bose-Einstein condensation)和原子波激射器(atom laser)的实现.     

Search for Higgs Boson in UHE Cosmic Rays

Considering the SM Higgs boson mass in the range of (95–235) GeV, we present here a mechanism for indirect searches of this scalar in UHE cosmic rays interactions. The mechanism is the decay of Higgs bosons which are produced through bubble formation due to vacuum excitation in an UHE cosmic rays interactions with air nuclei. We develop a model of hadronic interaction based on algorithms of the GENCL code of the UA5 experiment of CERN and some physics of CORSIKA code (Karlsruhe report), incorporating a fraction of energy transfer to bubble formation through vacuum excitation and subsequent multiparticle production via conversion of Higgs boson to heavy fermion pairs. Such events are expected to have high multiplicity and excess muons. This mechanism has significant effect starting from E _P 10¹⁸eV. It is found that the average muon number decreases gradually upto 175 GeV Higgs boson mass and remain practically constant thereafter for all primary energies (E _P) above 10¹⁸ eV and for all fractions of energy transfer (f _e 0.01–0.5). The fluctuation of muon multiplicity decreases with E _P and increases very slowly with Higgs mass upto 175 GeV, remaining practically invariant thereafter.     

Letter: Trace Anomaly and Backreaction of the Dynamical Casimir Effect

The Casimir energy for massless scalar field which satisfies periodic boundary conditions in two-dimensional domain wall background is calculated by making use of general properties of renormalized stress-tensor. The line element of domain wall is time dependent, the trace anomaly which is the nonvanishing T for a conformally invariant field after renormalization, represent the back reaction of the dynamical Casimir effect.     

Determination of the Coefficient of Laser Radiation Reflection from Dielectric Targets in Vacuum

We present the results of experimental determination of the coefficients of laser radiation reflection (₁ 10.6 m and ₂ 1.06 m) from dielectric targets of complex chemical composition in vacuum with allowance for a regime of developed plasma formation.     

基于双核模型对超重元素合成机制的研究

在双核模型基础上，考虑了熔合与准裂变的竞争，通过数值法求解主方程，计算了⁵⁰Ti，⁵⁸Fe+²⁰⁸Pb，²⁰⁹Bi这4个反应系统通过冷熔合反应合成超重元素的激发函数，得到了与实验比较符合的结果.计算了不同入射能量时各角动量分波对熔合概率和超重核存活概率的影响以及对蒸发剩余截面的贡献.这些结果对进一步理解超重核的合成机制有重要意义. 关键词： 超重元素 双核模型 熔合反应 蒸发剩余截面     

Kerr介质中双原子-压缩真空场系统的腔场谱

研究了含Kerr介质腔中耦合双原子间与双模均处于压缩真空态的光场拉曼相互作用过程的腔场谱.通过求解本征方程导出了双模光场处于任意强度时腔场谱的计算公式,给出了数值计算结果.发现在两模初始场均为弱场时,Kerr介质和原子间的耦合作用对谱结构的影响较小;当双模初始场均为强场时,两模主峰的右侧出现了半梳状边峰,随Kerr效应的增强,峰间距逐渐加宽,并向高频方向扩展,在Kerr效应较强时,两模边峰的峰高出现高低相间的现象.     

Influence of oxygen pressure of ZnO/glass substrate produced by pulsed filtered cathodic vacuum arc deposition

The effects of oxygen pressure on the structural and optical properties of high quality transparent conductive ZnO thin films were studied in detail. ZnO thin films were prepared by pulsed filtered cathodic vacuum arc deposition system under various oxygen pressures on glass substrate at room temperature. With increasing oxygen pressure, the structure and optical properties of films change. The structural and optical properties of the ZnO thin films were investigated using X-ray diffraction, transmittance spectrometry, refractive index, oscillator parameters, energy band gap and Urbach tail. The films show c-axis oriented (0 0 2) hexagonal wurtize crystal structure. It has been found that the grain size of ZnO thin films increases from 16.9 to 22.6 nm with the increase of oxygen pressure from 3.8×10⁻⁴ to 6.9×10⁻⁴ Torr and the crystallinity is enhanced. Average transmittance is about 90% in the visible region of the ZnO thin films. From optical transmittance spectra of ZnO films, the absorption edge shifts towards the taller wavelength with an increase in oxygen pressure. The energy band gap decreases from 3.31 to 3.20 eV with an increase in oxygen pressure. The packing density investigation shows in ZnO films high packing densities (above 0.78) can be obtained.     

Matrix-assisted pulsed laser evaporation of polyfluorene thin films

Poly(9,9-dioctylfluorene) (PF8) thin films have been deposited by matrix-assisted pulsed laser evaporation (MAPLE) using a KrF excimer laser. The influence of the laser fluence (50-500 mJ/cm²) and the nature of the solvent (chloroform, toluene, tetrahydrofuran) on the films properties have been studied. The chemical composition of the deposited films was investigated by Fourier transform infrared (FTIR) spectroscopy and compared with the one of spin coated films. To investigate the effect of the deposition parameters on the optical properties of the films, photoluminescence (PL) measurements were performed. Poor structural and optical properties were observed for films deposited starting from chloroform solutions. When using toluene as solvent, the spectra characteristics improved with increasing laser fluence, while wide PL spectra were observed. The characteristic emission bands of the PF8 polymer were nicely detected for films deposited starting from a tetrahydrofuran (THF) solution. Moreover, in this last case, the PF8 structure is preserved at high laser fluences, too.     

Polycaprolactone biopolymer thin films obtained by matrix assisted pulsed laser evaporation

We report the successful deposition of polycaprolactone polymer by MAPLE using a KrF* excimer laser (λ = 248 nm, τ = 7 ns). According to FTIR spectra the deposited films have similar chemical structure to the dropcast material. The fluence plays a key role in optimizing the performances of MAPLE-synthesized polycaprolactone structures. We demonstrated that MAPLE allows for controlling the morphology of films to the level required in targeted drug delivery of pharmacologic agents.