测定J/ψ辐射衰变产物自旋宇称方法的灵敏区研究

当J/φ辐射衰变产物X是两个赝标介子的束缚态时,螺旋性振幅理论给出了它的角分布W_J.我们注意到.用这个角分布来确定X的自旋宇称存在着不灵敏区.本文对不灵敏区问题作了进一步研究.结果表明:1)确实存在着不灵敏区;2)θ(1720)的自旋宇称是2~(++)还是0~(++)尚不能最后肯定;3)窄峰ξ(2230)如果存在的话,可以排除其自旋宇称是0~(++)的可能性.     

NaF和NaF：Mg^＋＋晶体色心光致电离研究

用337nm、380nm和510nm脉冲激光照射着色NaF和NaF:Mg~(++)晶体,皆能产生大量F_2~+心.在照射过的NaF:Mg~(++)晶体中,观测到了F_2~+ 心向(F_2~+)~*心的转型现象.     

ξ(2230)的胶子球解释

本文讨论了ξ(2230)作为胶子球解释的可能性.螺旋性振幅之比x和y的理论值与实验值的比较表明,ξ(2230)不可能是一个纯的2~(++)S波(或D波)的胶子球,但可能是一个4~(++)D波胶子球.     

爆轰波在炸药-金属界面上的折射分析

针对爆轰波在炸药-金属界面上折射时由实验获得的金属折射冲击波压力与经典爆轰波极曲线理论预测的压力存在显著差异这一问题, 本文展开了进一步的理论和数值模拟分析研究. 首先通过分析指出经典爆轰波极曲线理论的缺陷, 并对爆轰波极曲线理论进行了改进, 改进爆轰波极曲线理论给出了炸药爆轰波折射类型以及折射冲击作用点处的压力值. 然后发展了一个基于次特征理论来数值求解爆轰反应流动控制方程的二阶中心型Lagrange方法, 并数值模拟了一个典型的炸药爆轰波折射实验. 改进爆轰波极曲线理论和数值模拟分析结果表明, 爆轰波折射类型有三种:反射冲击波的正规折射、带Mach反射的非正规折射、无反射波的正规折射, 并且金属折射冲击波压力值随入射角增大而单调减小.     

金属卟啉化合物激发态折射与激发态吸收增强瞬态热折射竞争研究

应用激发态吸收增强瞬态热折射理论结合激发态折射理论研究了新型锌卟啉化合物Zn-porphyrin 中激发态吸收增强瞬态热折射与激发态折射间的相互竞争. 样品在不同脉宽激光激发下呈现自聚焦-自散焦间的转化. 当入射激光脉宽为4 ns时,激发态折射占主要地位,样品呈现自聚焦性质;当入射激光脉宽为8ns时,激发态吸收增强瞬态热折射占主要地位,激发态折射占次要地位,样品呈现自散焦性质. 关键词： 金属卟啉化合物 激发态折射 瞬态热折射     

包钴型γ—Fe_2O_3磁粉矫顽力增大原因的探讨

针状γ-Fe_2O_3磁粉与Co~(++)和Fe~(++)溶液或Co(OH)_2起反应,在每颗颗粒上包上了一层Co铁氧体。经这样处理后的γ-Fe_2O_3磁粉的矫顽力可由原来的420Oe增大到770Oe左右。研究了这种磁粉的矫顽力H_c随磁粉密度以及温度的变化等,认为这种磁粉矫顽力增大的原因是由于增加了磁粉的表面各向异性所致     

从负折射现象重新认识波

负折射现象是近年来被大量研究的一类有趣现象,它使人们对波动现象有了更深的理解,并推动了电磁新材料研究的发展.但是,负折射材料与通常正折射材料有很大不同,其中的物理原理不容易理解.文章用简单易懂的理论推演分析了负折射现象的物理起源,重新审视了波动方程的求解过程,并讨论了负折射现象给我们带来的启示.     

Compton散射对斜入射激光脉冲在等离子体中传输的影响

应用多光子非线性Compton散射模型和等效折射指数模型,研究了Compton散射对斜入射激光脉冲在等离子体中传输特性的影响,提出了将入射光和Compton散射光形成的耦合光脉冲作为在等离子体中传输的新机制,用等效耦合折射指数和折射定律分别计算和数值模拟了等离子体中耦合光的反射和折射,结果表明,散射使等离子体中法拉第效应增强,产生了一个与折射界面平行的、较小等幅度附加折射波平面;使等效耦合折射指数的实部和虚部的实参数、折射角和等效折射指数之间的差异明显减小;使用等效耦合折射指数和折射定所得到的反射系数几乎均表现出相同的先增大后迅速减小的规律;使等离子体的反射系数随碰撞频率的增大而迅速减小,透射增强,透射增强的频率位置向高频明显移动。     

Compton散射对斜入射激光脉冲在等离子体中传输的影响

应用多光子非线性Compton散射模型和等效折射指数模型,研究了Compton散射对斜入射激光脉冲在等离子体中传输特性的影响,提出了将入射光和Compton散射光形成的耦合光脉冲作为在等离子体中传输的新机制,用等效耦合折射指数和折射定律分别计算和数值模拟了等离子体中耦合光的反射和折射,结果表明,散射使等离子体中法拉第效应增强,产生了一个与折射界面平行的、较小等幅度附加折射波平面;使等效耦合折射指数的实部和虚部的实参数、折射角和等效折射指数之间的差异明显减小;使用等效耦合折射指数和折射定所得到的反射系数几乎均表现出相同的先增大后迅速减小的规律;使等离子体的反射系数随碰撞频率的增大而迅速减小,透射增强,透射增强的频率位置向高频明显移动。     

用于相位突变界面的广义的反射定律和折射定律

考虑到位于两物质界面上的Metasurface对光线传播行为的影响, 从费马原理和边界条件连续两种角度出发, 推导了可用于相位突变界面的广义反射与折射定律. 该定律在界面对光波的相位改变量为零的情况下, 回归为通常的反射定律和折射定律. 利用广义的折射定律和反射定律讨论了介质折射率、界面上的相位梯度等因素对光传播行为的影响, 发现利用广义的折射定律和反射定律很容易实现反常反射和反常折射行为, 并给出了出现反常反射和反常折射的条件, 以此为基础可以实现对光波的随意控制. 依据广义的折射定律和反射定律分析了一维相位掩模板对光场传播行为的影响. 关键词： 超材料 相位突变界面 反射定律 折射定律     

聚焦激光束加热时脉冲光热偏转光谱的理论及构型优化

本文给出了聚焦激光束加热时脉冲光热偏光谱的理论，考虑了加热束传输特性和探测束有限尺寸的影响，比较了各种理论模型及其适用范围，并对紧聚焦激光束加执焊脉冲光热偏转光谱的各项结构参数进行了优化。     

Photothermal techniques with a top-hat beam excitation

A flatly topped circular beam (“top-hat beam”) is employed as the excitation beam for photothermal deflection and surface thermal lens techniques. The Fresnel diffraction model is applied to describe the photothermal signals. The theoretical comparison between a Gaussian beam and a top-hat beam excited photothermal signal amplitudes shows that the use of the top-hat beam excitation improves the measurement sensitivity of the photothermal techniques. Experimental results for both photothermal deflection and surface thermal lens are presented. The potential applications of the top-hat beam excited photothermal techniques are highlighted.     

Negative refraction at infrared wavelengths in a two-dimensional photonic crystal

We report on the first experimental evidence of negative refraction at telecommunication wavelengths by a two-dimensional photonic crystal field. Samples were fabricated by chemically assisted ion beam etching in the InP-based low-index constrast system. Experiments of beam imaging and light collection show light focusing by the photonic crystal field. Finite-difference time-domain simulations confirm that the observed focusing is due to negative refraction in the photonic crystal area.     

Thermal loss mechanism in the generation of multifrequency laser emission via stimulated Raman scattering and four-wave Raman mixing studied by photothermal refraction spectroscopy

The heat produced in conjunction with the processes of stimulated Raman scattering and four-wave Raman mixing in hydrogen was measured by photothermal refraction spectroscopy. Many vibrational, rotational, and vibrationally shifted rotational Raman lines are exclusively/simultaneously generated by changing the polarization of the laser beam and the hydrogen pressure. Thermal loss occurs predominantly from vibrational Raman scattering, which can be ascribed to a large Raman shift frequency of 4155 cm^-1 for the vibrational transition. In contrast to stimulated Raman scattering, little or no thermal loss is observable during the process of four-wave Raman mixing. Received: 12 April 1999 / Revised version: 12 July 1999 / Published online: 20 October 1999     

基于椭圆偏振光谱法的玻璃表面离子束改性分析

采用阳极层线性离子源解离氮气对玻璃表面进行刻蚀处理,研究表面改性后玻璃表面的变化,并分析离化电压对表面粗糙度、折射率以及光学厚度的影响。在此基础上,基于椭圆偏振光谱仪,通过对比不同表面状态下的Δ光谱,讨论固定波长变化入射角的Δ光谱曲线特征与表面折射率、布儒斯特角、粗糙度以及光学厚度之间的关系。结果表明,刻蚀后玻璃的布儒斯特角附近的Δ光谱曲线形状发生变化,突变向高角度偏移,曲线下降斜率增大。通过建模并拟合分析发现,氮离子束轰击使玻璃表面产生光密介质层,表面折射率增大,布儒斯特角增大,粗糙度降低,且随离化电压升高,折射率不变,而光密介质层厚度增加。由原子力显微镜分析表面形貌,验证了离子束对玻璃表面的平整化作用。X射线光电子能谱结果表明离子束使玻璃表面发生选择性溅射,推断光密介质层的产生来自于离子束对玻璃表面的夯实作用。此外,推导并验证了Δ光谱曲线的特征与材料表面状态之间的普适关系,提出了基于椭圆偏振光谱仪的材料表面评估方法,即Δ曲线的突变发生角度增大说明折射率与布儒斯特角的增大;下降斜率增大说明表面粗糙度减小;曲线两端尖角增大说明光学厚度增大。反之亦然。     

Properties of Cu film and Ti/Cu film on polyimide prepared by ion beam techniques

Cu film and Ti/Cu film on polyimide substrate were prepared by ion implantation and ion beam assisted deposition (IBAD) techniques. Three-dimension white-light interfering profilometer was used to measure thickness of each film. The thickness of the Cu film and Ti/Cu film ranged between 490 nm and 640 nm. The depth profile, surface morphology, roughness, adhesion, nanohardness, and modulus of the Cu and Ti/Cu films were measured by scanning Auger nanoprobe (SAN), atomic force microscopy (AFM), and nanoindenter, respectively. The polyimide substrates irradiated with argon ions were analyzed by scanning electron microscopy (SEM) and AFM. The results suggested that both the Cu film and Ti/Cu film were of good adhesion with polyimide substrate, and ion beam techniques were suitable to prepare thin metal film on polyimide.     

Use of the direct negative Cu ion beam deposition for the control of the properties of Cu thin film

Direct metal ion beam deposition (DMIBD) technique for Cu thin film metallization is characterized. With suitable operating conditions, secondary Cu⁻ ion yield, ion/atom arrival rate ratio, ion beam energy spreads were optimized at 15%, 0.3, and 10%, respectively.After optimization of DMIBD system, the effect of Cu ion beam energy on the resistivity, adhesion strength, and surface morphology of Cu thin film was investigated. TEM micrograph shows that the film prepared at 75 eV was polycrystalline, while the film prepared at 0 eV was vertical columnar structure.As ion beam energy is increased from 25 to 75 eV, the resistivity is decreased from 6.21 to 2.09 μΩ cm, while the critical load to cause adhesion failure was increased to about 13 N at 200 eV, which is four-times higher that that of 25 eV.     

黑腔中高斯型激光束偏折的模拟研究

利用三维激光等离子体相互作用流体程序LAP3D数值模拟研究了高斯光束在均匀等离子体传播过程中的激光束偏折现象,分别考察了激光强度变化和等离子体横向流的流速变化对束偏折的影响。模拟结果表明:当流速接近离子声速时,激光束偏折效应最明显,此时激光偏折程度与激光强度成正比;当流速逐渐小于离子声速时,激光束偏折行为受抑制逐渐减弱;而当流速逐渐大于离子声速时,激光光强包络的变化以衍射效应为主。     

Gaussian beam parameter transformation at a refracting surface

The Fourier transform method is used to calculate the electric field of the astigmatic gaussian beam which appears when an incident stigmatic gaussian beam is refracted at the interface between media with different refractive indices. A beam parameter transformation law is derived which shows that the beam parameters of the refracted astigmatic beam can be calculated from the beam parameters of the incident stigmatic beam and the angles of incidence and refraction. An heuristic derivation of the transformation law based on geometrical optics is also given. The application of the law is illustrated by determining the plane parallel plate astigmatism.     

重离子束辐照对荷颊囊癌金黄地鼠血清微量元素的影响

探讨了重离子束辐照后荷颊囊癌金黄地鼠血清中微量元素含量的变化趋势。采用0, 4, 6, 8和12 Gy剂量的12C6+ 离子束对荷颊囊癌金黄地鼠辐照治疗后28 d取血, 应用原子吸收光谱仪火焰法测定血清中Fe, Cu, Zn, Mg和Ca 5种微量元素的含量。金黄地鼠成瘤后, 血清中微量Cu, Zn, Ca和Mg元素含量下降, 均明显低于正常组（P<0.05）; 不同剂量的重离子束辐照后28 d, 血清中5种微量元素在低剂量时均呈现继续下降趋势, 在6或8 Gy时恢复到正常组水平, 到12 Gy再呈降低的趋势, 存在一定的剂量-反应关系。重离子束辐照影响荷颊囊癌金地鼠血清微量元素的含量, 具有一定的临床意义。 To study the trend of the changes of trace elements in serum of golden hamster with cheek pouch carcinoma after irradiation by heavy ion beam, the cheek pouch carcinoma of golden hamster was exposed to different doses of heavy ion beam, after 4 weeks, the contents of Cu, Zn, Fe, Mg and Ca in serum were detected by flame method of Atomic Absorption Spectrometer. The contents of Cu, Zn, Ca and Mg in experimental groups with cheek pouch carcinoma were significantly lower than that of the normal group (P<0.05). After irradiated by 0, 4, 6, 8, 12 Gy heavy ion beam, the 4 Gy group showed a tendency downward, when the irradiation dose reached 6 Gy, the contents of Fe, Zn were increased, and decreased at 12 Gy. While Cu, Ca and Mg content of 8 Gy group rose to the highest, and decreased at 12 Gy. All of the results showed a dose reaction relationship (P<0.05). The irradiation of heavy ion beam maybe significantly affect the content of trace elements in serum of golden hamster with cheek pouch carcinoma.