环戊酮光电离解离的实验和理论研究

本文介绍了真空紫外光电离质谱结合理论计算研究环戊酮单分子的光电离解离过程. 在9.0∽15.5 eV能量范围内,测量了环戊酮离子及其碎片离子的光电离效率曲线. 通过光电离效率曲线,将环戊酮分子的电离能确定为9.23±0.03 eV,并确认碎片离子为：C₅H₇O⁺,C₄H₅O⁺,C₄H₈⁺,C₃H₃O⁺,C₄H₆⁺,C₂H₄O⁺,C₃H₆⁺,C₃H₅⁺,C₃H₄⁺,C₃H₃⁺,C₂H₅⁺, C₂H₄⁺. 利用量子化学计算方法,在ωB97X-D/6-31+G(d,p)理论水平基础上,提出了C₅H₈O⁺的解离机制. 通过对环戊酮解离路径的分析,发现开环和氢迁移过程为环戊酮离子解离的主要路径.     

异戊二烯解离光电离理论研究

利用CBS-QB3理论计算方法研究了异戊二烯的可能解离通道.获得了主要碎片离子C₅H₇⁺,C₅H₅⁺,C₄H₅⁺,C₃H₆⁺,C₃H₅⁺,C₃H₄⁺,C₃H₃⁺的C₂H₃⁺的结构以及这些解离通道的解离能,并给出了相应的过渡态和中间体的结构和位垒.得到的异戊二烯电离势及主要碎片离子的出现势均与实验值符合的较好.最后,通过理论和实验结果的对比讨论了各通道的解离机理.     

高能正负电子对的湮没与超窄共振ψ粒子的作用

本文给出了R=(σ(e⁺e^-→强子))/(σ(e⁺e^-→μ⁺μ^-))随能量上涨的一个解释。研究了新发现ψ粒子所具有作用的性质,指出其强度f²/(4π)～10^-5—10^-6。求得峰值截面σ₀=(12π)/m_ψ²(Γ(ψ→e⁺e     

小变形原子核中的相干效应

本文考察了在转动的小变形核力场中运动的核子-核子对、核子-空穴对中的相干效应。计算了O¹⁸最低的偶宇称态0⁺,2⁺,4⁺和O¹⁶最低的奇宇称态0^-,1^-,2^-,3^-波函数;和壳模型经典方法计算出的结果作了比较,二者相当一致。得出的初步结论如下:核力主要是P₂力再加上一定成分具有相干性质的力。前者与转动的变形场等效。不但对于0⁺,2⁺,4⁺,3^-态,而且对于1^-,2^-态,附加的相干成分都很重要;它们的内部态混合组态是比较多的,粒子-粒子之间、或粒子-空穴之间的关联都比较显著。只有0^-态的内部态是纯组态。     

钒氧卟啉正负离子的结构畸变与电子-振动耦合的DFT研究

用PBE1PBE方法研究了钒氧卟啉一价阴离子([VOP]^-)、一价阳离子([VOP]⁺)的单态和三重态结构. 结果表明[VOP]^-和[VOP]⁺的最稳定电子态均为三重态,其未配对电子一个占据钒的d_xy轨道,另一个占据卟啉环的π轨道,因此两者均为π-自由基. 中性分子(VOP)的双重态最稳定,其未配对电子占据钒的d_xy轨道. 双重态VOP具有较高的C_4v对称性,而三重态[VOP]^- 离子由于发生姜-泰勒效应对称性降低为C_2v. 计算了[VOP]^-姜-泰勒活性振动模式的电子-振动耦合常数,并用前线KS轨道的节面分布解释了姜-泰勒畸变沿特定简正模式发生的原因. 三重态[VOP]⁺ 阳离子的卟啉环发生键长交替变化,构型畸变起源于电子态近简并引起的赝姜-泰勒效应,导致其对称性从C_4v降低为C₄,其结构变化可以用重组的前线KS轨道的节面分布解释.     

甲基环己烷在9∽15.5 eV能量区的真空紫外光电离研究

利用具有同步辐射源的反射式飞行时间质谱仪，研究甲基环己烷的真空紫外光电离和光解离. 观测到母体离子C₇H₁₄⁺和碎片离子C₇H₁₃⁺，C₆H₁₁⁺，C₆H₁₀⁺，C₅H₁₀⁺，C₅H₉⁺，C₄H₈⁺，C₄H₇⁺和C₃H₅⁺的光电离效率曲线. 测定甲基环己烷的电离能为9.80±0.03 eV，通过光电离效率曲线确定其碎片离子的出现势. 在B3LYP/6-31G(d)水平上对过渡态、中间体和产物离子的优化结构进行表征，并使用G3B3方法计算其能量. 提出主要碎片离子的形成通道. 分子内氢迁移和碳开环是甲基环己烷裂解途径中最重要的过程.     

辅助光对NaCl(OH-)和KCl(Na+,OH-)晶体中的类F2+型色心激光输出的影响

文中报进了有关辅助光对NaCl(OH^-):(F₂⁺)_H及KCl(Na⁺,OH^-):(F₂⁺)_AH色心激光输出功率影响的主要研究结果。初步探讨了辅助光作用的物理机制。     

AlnC4-/0(n=2∽4)团簇的结构和成键性质: 光电子能谱和理论计算

本文采用尺寸选择的负离子光电子能谱与高精度理论计算,对Al_nC₄^-/0(n=2∽4))团簇的结构和成键性质进行了研究. Al₂C₄^-团簇负离子的最稳定结构是一个C_2v对称的平面结构,其中两个C₂单元与两个铝原子分别相连. Al₂C₄^-团簇负离子的次稳定结构是一个线型结构,两个铝原子位于C₄线型结构两端,能量仅比最稳定结构高0.05 eV. 中性Al₂C₄团簇是一个线型结构. Al₃C₄^-团簇负离子是一个平面结构,其中三个铝原子分别与两个C₂单元相连. 而中性Al₃C₄团簇则是一个V字型结构. Al₄C₄^-团簇负离子和中性Al₄C₄团簇均为C_2h对称的平面结构,四个铝原子分别位于两个C₂单元的末端. Al_nC₄^-/0(n=2∽4))团簇负离子的自适应自然密度配分的分析结果表明这些团簇中铝原子与C₂单元之间的化学键具有σ和π键特征.     

碘酸锂晶体全部电弹常数的测量

本文探讨了碘酸锂晶体(α-LiIO₃,简称LI)全部电弹常数的测试方法。以压电板厚度振动模理论,推导出LI晶体独立电弹常数计算公式。对无压电耦合的弹性常数C₁₁^E和C₆₆^E,采用了声光同步测速法进行测量。最后,测量给出了LI晶体全部电弹常数和一些机电耦合系数共52个数据。     

ILC上Z玻色子与荷电top-pion对联合产生过程的研究

在国际直线对撞机(ILC)上顶色辅助的人工色(TC2)模型下对Z玻色子与荷电top-pion对联合产生过程e⁺e^- → Zπ_t⁺π_t^-进行了研究. 计算了过程e⁺e^- → Zπ_t⁺π_t^-的产生截面, 发现在TC2模型所允许的参数空间范围之内该过程的截面最大可达到1 fb. 考虑到荷电top-pion的主要的衰变模式π_t⁺ → tb, 发现该截面在ILC能产生很可观的事例数.     

Hyperfine structure in optical spectra of LiYF4-Ho3+: forbidden transitions

The hyperfine lines of the forbidden Γ₃₄?→?Γ₃₄ optical transition are observed in the axially polarized absorption spectra of Ho³⁺ in LiYF₄. They are explained by an admixture of nearby lying Γ₂ and Γ₁ crystal field states by the perpendicular part of the magnetic dipole hyperfine interaction.     

Etude de l'intensité d'oscillateur de la raie d'absorption quadrupolairen=1 de la série jaune de Cu2O à 4,2°K

The oscillator strength of the orthoexcitonicn=1 line of the yellow series of Cu₂O has been measured at 4,2°K. Its value for a polycrystalline sample and for unpolarized light isf=1,3·10^?9. The variation of intensity of the line as a function of the orientation of the light vectorq with respect to the symmetry axes of the crystal has been determined with natural, oriented single crystals. The results obtained are in good agreement withElliott's theory. According to this theory, this line corresponds to an excitonic electric quadrupole transition. The transition takes place from a ground level of representationΓ ₁ ⁺ towards an excitonic level of representationΓ ₂₅ ⁺. In the red part of the spectrum, we have observed with thick oriented monocrystalline samples of natural Cu₂O two new lines of weak intensity. The origin of these lines is discussed.     

Optical absorption due to paraexciton of Cu2O

In Cu₂O a new absorption line is observed at 97 cm^?1 below the n =1 of the yellow exciton (triply degenerate orthoexciton) under a strong magnetic field at 4.2 K. The line is assigned as a transition to a nondegenerate spin triplet state Γ⁺₂ (paraexciton). An analysis including the effects due to the n =1 of the green exciton yields 364 cm^?1 as the exchange energy, and 2.68 and ?1.02, or 1.02 and ?2.68 as the g-factors of the conduction and valence bands forming the yellow exciton.     

Valence band spin-orbit splitting in CdTe and Cdf−xMnxTe and giant zeeman effect in the Γ7 band of Cd1−xMnxTe

Optical transitions from spin-orbit split-off valence band Γ₇ to the conduction band Γ₆ were directly observed in transmission measurements on thin samples of CdTe and Cd_1?xMn_xTe. Precise values of spin-orbit splittings were determined. Giant Zeeman splitting of Γ₇ - Γ₆ exciton in Cd_1?xMn_xTe was observed and found coherent with corresponding splitting of Γ₈-Γ₆ exciton.     

Electronic absorption spectra of the 5d3 hexafluororhenate(IV) ion

The Γ₈(⁴A_2g) →Γ₇(²T_2g), Γ₈(²T_2g) electronic transitions for the 5d³ hexafluororhenate(IV) ion have been observed at liquid hydrogen temperature in a single Cs₂GeF₆ crystal and in a mixed crystal where the ReF^?2₆ ion is doped in the cubic Cs₂GeF₆ lattice. The electronic transitions have been assigned with a crystal field model to give information about the parameters B, C, Dq, and spin-orbit coupling. The vibrational structure in the mixed crystal system may be assigned to the ungerade modes of the ReF^?2₆ moiety. Comparison of the mixed and pure crystal vibrational structure shows that the pure crystal vibrational structure can be interpreted on the basis of K ≠ 0 lattice effects and a small distortion in the pure crystal.     

Magnetooptical evidence of exchange interactions in zero-gap Hg1−xFexTe mixed crystals

Interband magnetoabsorption is carried out on zero gap Hg_1-xFe_xTe alloys of x ～ 0.015.Γ₆ → Γ₈ magnetooptical spectra for σ⁺, σ^-, γ 6 H polarization are quantitatively interpreted within the “quasi Ge” model modified by the inclusion of exchange contributions. The field dependence of the magnetization provides evidence of antiferromagnetic interactions between localized spins.     

The nature of excitonic complexes in ZnTe

Uniaxial stress experiments were used to investigate the nature of the luminescence lines observed at low temperatures in ZnTe in the vicinity of the absorption edge. The single crystals used in this experiment were grown from solution of ZnTe in tellurium. Both “as-grown” crystals and crystals annealed in Zn vapour were investigated. The most intense line in “as-grown” crystals is attributed to an exciton bound to a neutral acceptor. The binding energy of the exciton in this center is 6 meV. After annealing a new center appears in the same spectral region. Stress experiments as well as the temperature dependence of the intensity of the luminescence indicate that this center is a complex consisting of an exciton and an ionized donor. Splitting of J = 1 (Γ₅) and J = 2 (Γ₃ + Γ₄) levels was found to be 1.2 meV.     

掺铒硅发光的晶场分裂

测量了掺铒硅的高分辨光致发光光谱，得到9条铒发光分裂谱线.利用群对称理论指出9条谱线来自Er³⁺中⁴I_13/2到⁴I_15/2光跃迁在T_d晶场下的分裂.Er³⁺的第一激发态⁴I_13/2最低能量的两个Stark能级为Γ₈，Γ₆(能量递增)，它们到基态⁴关键词：     

Magneto-optical studies of excitons in AgGaS2

The reflection, absorption and luminescence spectra of the lowest excitons in AgGaS₂ are measured in magnetic fields. The results can be explained by the quasicubic model. The exchange splittings of the Γ₄, Γ₅ and Γ₃ exciton state are evaluated. The Zeeman splittings of the Γ₅ and Γ₅-Γ₃ states yield g-values of + 3.8 and 3.7, respectively. They are determined mainly by the contributions of the hole and conduction electron spins.     

Vibronic model of the stress effects on the relaxed excited state of the F center

A vibronic model of the stress effects on the relaxed excited state of the F center is studied by taking into account the Γ⁺₁, Γ⁺₃, and Γ^-₄-mode phonons. The vibronic parameters and stress coupling coefficients are determined for KCl. The orbital reduction is discussed.