Structural Deformation of CO22+ in Intense Femtosecond Laser Fields

The angular distributions of CO^＋ from the dissociation of CO2^2＋ and CO2^＋ in intense femtosecond laser fields （45 fs, about 5 × 10^15 W/cm^2） are studied at a laser wavelength of 800nm based on the time-of-flight mass spectra of CO^＋ fragment ions. The experimental results show that structural deformation occurs in the charge state of CO2^2＋ and the CO^＋ maintains linear geometrical structure.     

双光束相干控制产生多次谐波的实验验证

利用两束相干度可改变的飞秒脉冲光对产生的五次谐波的强度特性进行了研究，发现谐波信号的强度随相干程度的增大而增加，谐波信号的最大值相对于相干零点(双光束相干度最大处)是非对称的，从而证明了合成的激光脉冲波形变化对谐波信号的影响.同时对谐波的受激放大理论进行了初步的实验探索和展望. 关键词： 五次谐波 波形变化 相干 受激放大     

KrF激光受激布里渊散射反射率稳定性的研究

实验研究发现抽运功率密度（或抽运能量）的波动引起的受激布里渊散射(SBS)反射率的不稳定程度受实验参数（抽运能量、介质气压和透镜焦距）的影响.当抽运能量、介质气压和透镜焦距这三个参数同时满足下列条件时可以获得稳定的输出：抽运能量超过5倍的SBS阈值，介质气压在16×105Pa和透镜焦距在15—50cm的范围内；同时还发现当改变实验参数时SBS反射率与稳定性的变化规律完全一致，反射率越高稳定性越好.通过理论分析得到 SBS反射率的相对稳定度实际上是受GIL因子的影响，理论计算与实验符合得很好. 关键词： KrF激光 受激布里渊散射 反射率 稳定度     

对撞增强型YAG相位共轭腔

降低SBS相位共轭腔的启动阈值以及如何提高输出光束的质量一直是人们关心的课题。报道了在YAG激光器上运行一种新型对撞增强型YAG受激布里渊散射相位共轭激光腔的输出特性。该腔具有较低的启动阈值和较高的输出能量;该腔型最高能输出150mJ的能量,输出脉宽最窄为11ns,光束发散角为1.3mrad,输出能量和光束质量都很优良。     

Lifetimes of Excited Levels in ^131Ce

The fusion-evaporation reaction ^116Sn (^19F, p3n)^131 Ce at projectile energy of 95 MeV is used to populate high spin states in ^131Ce. The de-exciting γ-rays are detected in γ-γ coincidence measurement with Compton-suppressed BGO-HPGe detectors. Level lifetimes of ^131 Ce were determined by using the Doppler shift attenuation method.The experimental results indicate that collectivity of ^131 Ce is reduced relative to that of ^130Ce and it follows that deformation decreases with increase of the neutron number on the basis of systematic comparison of transition quadrupole moments for the light cerium isotopes.     

Photoluminescence Characterization of Silicon Nanoparticles Hybridized Europium Complex

A europium complex Eu (DBM)3 TPPO (Eu tris(benzoylmethide)-(triphenylphosphine oxide)) and silicon nanoparticles have been hybridized.The hybridization can evidently change the photoluminescence (PL) characteristics of the Eu complex in the following aspects:under an excitation of 390nm,the intensity of the PL peak at 611nm due to the ^5Du-^7F2 transition of the Eu^3 ions has been increased by 30%,and thc integrated PL intensity in the visible range has been increased by nearly 3 times;the PL excitation efficiency beyond 440nm has been improved cvidently;the peak in the PL excitation spectrum shifts from 408nm to 388nm,and the PL decay time decreases from 2.07 to 0.96μs,The experimental results indicatde that in the PL process,the photoexcited energy may transfer from the silicon nanoparticlcs to the Eu^3 ions.     

高电荷态离子126Xeq+与Ti固体表面作用的激发光谱

报道用150keV的高电荷态离子¹²⁶Xe^q+（6≤q≤30）轰击Ti固 体表面产生2 00—1000nm波段发射光谱的实验结果.结果显示，用电荷态足够高的离子作光谱激发源，无 需很强的束流强度（nA量级），便可激发起样品表面的原子和离子在可见光波段的特征谱线 .当入射离子剥离度q>q_c≈20时，Ti原子及其离子的特征谱线强度突然显著增强 ；不 同金属靶，特征谱线突然增强的q_c值不同.理论分析表明，这与q大于此临界值 后，单电子转移释放能量激发靶材料传导电子气体的表面等离激元密切相关. 关键词： 低速高电荷态离子 特征谱线 经典过垒模型 等离激元     

Optical limiting effect based on stimulated Brillouin scattering in CCl4

The optical limiting effect based on stimulated Brillouin scattering (SBS) in a nonlinear medium was investigated. We numerically treated the nonlinear propagation process with a theoretical model, which includes the spontaneous nature of the initiation of SBS, and obtained optical limiting effect in the process. Energy limiting, pulse reshaping and stabilization have been demonstrated on SBS mechanism with the nonlinear medium CCl_4. The input optical signals were Nd:YAG nanosecond laser pulses with width varying from 16ns to 7ns then to 2ns, the relationship between the transmitted signal and launched pump signal was shown. In the experimental regime, the most stable pulse and a superior energy stabilization of the transmitted pulse were obtained when the laser pulse-width became as short as 2ns. For the energy variation of laser pulses in a wide range of 14－88mJ, the output energy was limited in a quite narrow range 4.5－5.5mJ.     

单模双折射光纤中的增益

在双折射光纤中,根据受激拉曼散射和参量放大共同作用下的斯托克斯波和反斯托克斯波所满足的耦合模方程,考虑输入泵浦波是线偏振光,推导出了与泵浦波偏振方向垂直的的斯托克斯波和反斯托克斯波的增益系数;研究了双折射色散缓变光纤中,斯托克斯波和反斯托克斯波增益随相关参量的变化关系。结果表明,与泵浦波偏振方向垂直的斯托克斯波和反斯托克斯波增益的变化趋势是完全相同和对称的;同时表明,通过改变失配系数 ,在适当的传输位置,可以实现对斯托克斯波和反斯托克斯波有选择性的输出,以达到输出频率转换的目的。     

一维金属光栅的光学反射吸收

利用RCWA(rigid coupled-wave analysis)方法研究了一维金属光栅的反射特性,考察了 瑞利反常、表面等离激元驻波共振和几何共振三种共振吸收机理,分析了这三种机理的相互作用,如表面等离激元驻波共振和几何共振可以形成混合模式. 在反射式复合金属光栅中,确认了第四种共振形式,即相位共振. 数值计算表明相位共振对光学吸收的影响有两种形式: 当光栅周期大于一个波长时,相位共振导致尖锐的吸收峰,峰位在几何共振吸收峰一侧;当光栅周期小于一个波长时,相位共振导致混合模式的共振吸收峰发生劈裂. 对一维金属光栅反射特性的研究增加了对金属光栅共振吸收模式及其相互作用的认识. 关键词： 一维金属光栅 瑞利反常 表面等离激元 相位共振