Selection rules for electric multipole transition of diatomic molecule in scattering experiments

The knowledge of the energy level structures of atoms and molecules is mainly obtained by spectroscopic experiments.Both photoabsorption and photoemission spectra are subject to the electric dipole selection rules(also known as optical selection rules). However, the selection rules for atoms and molecules in the scattering experiments are not identical to those in the optical experiments. In this paper, based on the theory of the molecular point group, the selection rules are derived and summarized for the electric monopole, electric dipole, electric quadrupole, and electric octupole transitions of diatomic molecules under the first Born approximation in scattering experiments. Then based on the derived selection rules, the electron scattering spectra and x-ray scattering spectra of H2, N2, and CO at different momentum transfers are explained, and the discrepancies between the previous experimental results measured by different groups are elucidated.     

利用近似理论计算原子分子形状因子的平方

实现了基于近似理论数值计算原子基态形状因子平方的方法,并以氢原子为例,检验了Hatree-Fock近似方法与密度泛函近似方法的优劣,对比了不同基组的精确性.这种数值计算方法也适用于揭示其他波函数无法精确求解的原子和分子的电子结构.     

1,2-环氧辛烷的同步辐射光电离解离研究

利用同步辐射产生的真空紫外光和反射式飞行时间质谱仪,在超声冷却条件下测量了1,2-环氧辛烷在光子能量9.8~16.6 eV能区的光电离解离过程,获得了不同能量光子作用下的电离解离产物。通过测量各离子的光电离效率曲线,得到了主要碎片离子的出现势。结合G3理论计算得到了母体离子、中性碎片及离子碎片的结构与能量,通过对比实验测量值与理论值给出了1,2-环氧辛烷的光电离解离通道.     

A review of recent theoretical and computational studies on pinned surface nanobubbles

The observations of long-lived surface nanobubbles in various experiments have presented a theoretical challenge, as they were supposed to be dissolved in microseconds owing to the high Laplace pressure. However, an increasing number of studies suggest that contact line pinning, together with certain levels of oversaturation, is responsible for the anomalous stability of surface nanobubbles. This mechanism can interpret most characteristics of surface nanobubbles. Here, we summarize recent theoretical and computational work to explain how the surface nanobubbles become stable with contact line pinning. Other related work devoted to understanding the unusual behaviors of pinned surface nanobubbles is also reviewed here.     

氮分子{a'^1}\Sigma _g^ (v' = 0)和{a'^1}\Sigma _g^ + (v' = 1) + {b^1}\Pi _u(v' = 0) 广义振子强度的高能电子散射研究

利用快电子能量损失谱仪结合相对流量技术,在入射电子能量1500 eV和能量分辨70 meV的条件下,测量了氮分子{a''^1}\Sigma _g^ (v'' = 0)和{a''^1}\Sigma _g^ + (v'' = 1) + {b^1}\Pi _u(v'' = 0)激发态的广义振子强度。通过与已有的电子散射结果以及X射线散射结果对比发现,对于{a''^1}\Sigma _g^ (v'' = 0)和{a''^1}\Sigma _g^ + (v'' = 1) + {b^1}\Pi _u(v'' = 0),我们的结果与X射线散射结果在大动量转移出现差异,这表明对{a''^1}\Sigma _g^ (v'' = 0)和{a''^1}\Sigma _g^ (v'' = 1),即使入射电子能量1500 eV也没有达到一阶玻恩近似条件。在动量转移平方小于2 a.u.时, {a''^1}\Sigma _g^ + (v'' = 1) + {b^1}\Pi _u(v'' = 0)与X射线散射结果的符合表明,对{b^1}\Pi _u(v'' = 0),1500 eV入射电子能量已经达到一阶玻恩近似条件。     

氮分子a″~1Σ_g~+(v'=0)和a″~1Σ_g~+(v'=1)+b~1Π_u(v'=0)广义振子强度的高能电子散射研究

利用快电子能量损失谱仪结合相对流量技术,在入射电子能量1500 eV和能量分辨70 meV的条件下,测量了氮分子a″~1Σ_g~+(v'=0)和a″~1Σ_g~+(v'=1)+b~1Π_u(v'=0)激发态的广义振子强度.通过与已有的电子散射结果以及X射线散射结果对比发现,对于a″~1Σ_g~+(v'=0)和a″~1Σ_g~+(v'=1)+b~1Π_u(v'=0),我们的结果与X射线散射结果在大动量转移出现差异,这表明对a″~1Σ_g~+(v'=0)和a″~1Σ_g~+(v'=1),即使入射电子能量1500 eV也没有达到一阶玻恩近似条件.在动量转移平方小于2 a.u.时,a″~1Σ_g~+(v'=1)+b~1Π_u(v'=0)与X射线散射结果的符合表明,对b~1Π_u(v'=0),1500 eV入射电子能量已经达到一阶玻恩近似条件.     

离子液体的凝聚态化学研究

离子液体是可以替代传统溶剂实现高效、低碳、清洁、循环新过程新技术的新型溶剂,在完成“双碳”目标中具有重要的应用价值。同时,离子液体是一种典型的“软凝聚态物质(软物质)”,对它的认识和应用依赖于对其内部多尺度微观结构的研究,这需要以“凝聚态化学”的思想作为未来的研究方向,即对离子液体体系的组成、结构、性质、功能及它们之间的内在关系进行多层次的研究,进而实现对实际应用体系中传递过程和反应过程的调控。在本文中,我们以“凝聚态化学”的视角简要综述了对离子液体的研究。首先介绍了离子液体的化学结构和物理性质,指出理解离子液体性质的变化必须要研究其内部的结构。然后,我们介绍了离子液体从分子层面到纳微尺度的结构,包括离子对、氢键、氢键网络、团簇、界面结构和纳米限域结构。最后,我们对离子液体“凝聚态化学”研究的未来进行了展望。     

相对流量技术及其在电子碰撞微分散射截面测量中的应用

为了提高原子分子动力学参数的测量精度,本文把气体相对流量技术应用到快电子碰撞研究中. 并且在此基础上测量了氙原子6s激发的广义振子强度,所得结果在小动量转移区间与前人的结果符合很好,表明气体相对流量技术在电子碰撞方法中的适用性. 大动量转移区间6s的表观广义振子强度对电子碰撞能量的依赖行为,说明500eV的电子碰撞能量还不满足一阶玻恩近似条件. 与Hartree-Fock方法相比,考虑电子关联效应更全面的随机相移近似计算结果与本文的实验结果符合更好,说明对于像Xe这样的重原子,电子关联效应十分重要.     

Momentum transfer dependence behaviors of ionization and dissociation of oxygen

The decay pathways of the structured ionization region of oxygen at different momentum transfers,i.e.,0,0.23 a.u.(atomic unit),and 0.91 a.u.,are studied by measuring the ion and the scattered electron coincidently.It is found that the dipole-forbidden superexcited states of(2σu)-1(c4Σu-)npσu 3Σg-← X3Σg-decay into different channels according to the principal quantum number n.The broad ridge above 35 eV,which may be due to inner-valence excited states of(2σg)-1nλ or multiply excited states,is observed both at small and large momentum transfers,and its decay channel of O++ O is dominant.     

Oscillator strength study of the excitations of valence-shell of C2H2 by high-resolution inelastic x-ray scattering

The oscillator strengths of the valence-shell excitations of C₂H₂ are extremely important for testing theoretical models and studying interstellar gases. In this study, the high-resolution inelastic x-ray scattering (IXS) method is adopted to determine the generalized oscillator strengths (GOSs) of the valence-shell excitations of C₂H₂ at a photon energy of 10 keV. The GOSs are extrapolated to their zero limit to obtain the corresponding optical oscillator strengths (OOSs). Through taking a completely different experimental method of the IXS, the present results offer the high energy limit for electron collision to satisfy the first Born approximation (FBA) and cross-check the previous experimental and theoretical results independently. The comparisons indicate that an electron collision energy of 1500 eV is not enough for C₂H₂ to satisfy the FBA for the large squared momentum transfer, and the line saturation effect limits the accuracy of the OOSs measured by the photoabsorption method.