Identification of Above-Threshold Ionization by Imaging Photoelectrons from Ammonia Molecules in an Intense Femtosecond Laser Field

The above-threshold ionization process of ammonia molecules induced by a femtosecond laser field at 800 nm is studied in the intensity range from 1.6 × 10¹³ to 5.7 × 10¹³ W/cm². Channel switching under different laser intensities is observed and identified in the photoelectron kinetic energy spectra of ammonia. Based on the photoelectron kinetic energy distributions and the photoelectron angular distributions, the characteristic peaks observed are exclusively ass...     

由值域求定义域的问题值得商榷

不少的参考书及杂志上出现了如下的题目 :已知函数 ｙ =4 ｘ- 3·2 ｘ 3的值域为 [1,7],则它的定义域是 (　　 )(Ａ) [- 1,1]∪ [2 ,4 ].　　 (Ｂ) [2 ,4 ].(Ｃ) (-∞ ,0 )∪ [1,2 ]. (Ｄ) (1,2 ) .其所谓的正确解答过程为 :解　由题设得4 ｘ- 3·2 ｘ 3≤ 7,4 ｘ- 3·2 ｘ 3≥ 1 4 ｘ- 3·2 ｘ- 4≤ 04 ｘ- 3·2 ｘ 2≥ 0 - 1≤ 2 ｘ≤ 42 ｘ≥ 2或 2 ｘ≤ 1 - 1≤ 2 ｘ≤ 1或 2≤ 2 ｘ≤ 4 ｘ≤ 0或 1≤ｘ≤ 2 .故函数定义域为 :(-∞ ,0 ]∪ [1,2 ].但我们很容易验证 ,当该函数的定义域为 [1,2 ]时 ,函数的值域也是 [1,7],可见 ,本题…     

从随机到取向--分子转动动力学的超快调控

分子取向物理是研究如何操控分子空间排列方向以及如何制备具有特定方向的分子。近十多年来,分子取向物理学取得巨大进展,人们通过各种技术对分子取向物理进行研究,使人们对分子取向的认识达到一个全新的高度。文章首先介绍了分子的量子态及其分布,转动量子态选择方法和分子的转动动力学,然后概述通过制备和调控转动态的相干布居来控制分子取向的方法。实验和理论表明,分子的不同转动态在相同激光条件作用下产生的转动波包不一样,从而导致分子的准直和取向程度随时间演化完全不一样。通过选择合适的转动量子态能够很好地提高分子取向程度。取向分子作为相互作用靶,为原子分子动力学、精密测量物理、立体化学反应和表面碰撞过程等提供了更加丰富多彩的研究内容。     

静电六极装置电场分布的数值计算方法及在N2O分子转动态选择、取向中的应用

阐述求解极性分子转动态选择及取向静电六极装置中势能分布、电场分布的数值计算方法.为了获得电场分布公式,需通过数值迭代求解势能满足的Laplace方程,获取数值分布点,通过数值分布点,由待定系数的多级展开势能解析表达式进行最小二乘拟合获得势能分布公式,由势能对空间向量的微分获得电场分布.分子在六极电场中的运行轨迹采用经典Newton方程描述,并通过四阶龙格-库塔方法(Four Order Runge-Kutta Method)实现数值求解,其中能量处理采用量子力学方法.应用此方法给出静电六极装置的电场分布公式,运用获得的电场分布公式计算和讨论电场对极性分子N₂O的静电六极转动态选择、取向所带来的影响.     

Hexapole State-Selection and Beam Focus of Linear Triatomic Molecules

The state selection and beam focus of linear triatomic molecules （OCS, HCN, ClCN, BrCN and ICN） with doubling states in a hexapole electric field have been numerically realized. The method is based on a quantum mechanical treatment of the molecular Stark energy and a classical mechanical treatment for the molecular trajectory in the field. In linear molecules with doubling states, the second-order Stark effect can be neglected and the doubling states have the same value of J and M. The influences of the molecular properties, state energies, and the apparatus parameters such as molecular beam temperature and length of the hexapole, on the role of state selection and focus have been discussed. The method established here can be taken as a guide for hexapole experiment of orientation of polar molecules.     

B-型长不对称陀螺分子在六极静电场中的转动态选择和取向作用

运用王函数(Wang Function)组合构成转动波函数推导了不对称陀螺分子转动能及其在外电场作用下的Stark能量的表达式,并将其应用到六极静电场态选择理论计算中.使用类似简并能级的计算方法讨论了彼此接近能级情况下分子转动态选择情况,获得了对(CH3)2O、O3、SO2分子实现获得具有高各项异性取向的分子束的优化条件.     

First principles investigation on Li or Sn codoped hexagonal tungsten bronzes as the near-infrared shielding material

The 52% energy of the solar radiation is contributed by near-infrared radiation (NIR, 780-2500 nm). Therefore, the material design for the energy-saving smart window, which can effectively shield NIR and has acceptable visible transmittance, is vital to save the energy consumed on the temperature control system. It is important to find a non-toxic stable material with excellent NIR-shielding ability and acceptable visible transmittance. The systematic first-principles study on Li_xSn_yWO₃ (x=0, 0.33, 0.66, and y=0, 0.33) exhibits that the chemical stability is a positive correlation with the doping concentration. After doping, the Fermi-energy upshifts into the conduction band, and the material shows metal-like characteristics. Therefore, these structures Li_xSn_yWO₃ (except the structure with x=0.33 and y=0) show pronounced improvement of NIR shielding ability. Our results indicate that when x=0 and y=0.33, the material exhibits the strongest NIR-shielding ability, satisfying chemical stability, wide NIR-shielding range (780-2500 nm), and acceptable visible transmittance. This work provides a good choice for experimental study on NIR shielding material for the energy-saving window.     

六极装置电场分布及对CH3Cl分子束选态会聚的模拟

通过数值获得的六极装置内部电势分布数值解,拟合得出电势分布公式中的系数,给出各项系数随着装置参数ρ0/r0的变化规律及拟合函数形式,结果表明ρ0/r0=0.5516时,六极装置的电场分布最接近理想六极电场. 对于其它ρ0/r0值时,推导出电势、电场更精确的计算公式. 并利用这些公式,在ρ0/r0不满足最优配置时给出了对CH3Cl分子转动态的会聚所需的实验参数. 这些方法为利用六极装置对分子束会聚和转动态选择的理论模拟及试验提供了更准确的理论依据.