AlⅠ原子~2D吸收谱的多通道量子数亏损理论分析

本文用多通道量子数亏损理论分析计算了AlI原子的~2D吸收谱。采取具有三个不同电离阈的三个分解通道的混合模型。在适当选择了与能量有关的参数μ_α,D_α以及转换矩阵元U_(iα)之后,计算了第一电离阈和第二电离阈之间的~2D自电离谱,并与Roig的测量结果作了比较。利用上述参数延伸到分立能域,得到~2D能级的里德伯系列及其振子强度值。其结果与Lin和Weiss的分析以及相关的实验相符。     

Rb(62D)原子与基态Rb原子,H2分子碰撞转移截面

本文用荧光法测量Rb(6²D)原子与基态Rb原子,H₂分子碰撞转移截面。结果表明:Rb(6²D)-Rb(5²s)转移截面为σ_fs=67×10^-14cm²,σ_tr=4.3×10^-14cm²,Rb(6²D)—H₂转移截面为σ_fs 关键词：     

THE 82S1/2→62D EXCITATION TRANSFER OF RUBIDIUM ATOMS INDUCED BY COLLISIONS WITH GROUND-STATE RUBIDIUM AND HYDROGEN MOLECULES

The processes of excitation transfer from the 8²S_1/2 state to the 6²D state of rubidium in Rb(8²S_1/2)-Rb(5²S_1/2) and Rb(8²S_1/2)-H₂ collisions have been studied experimentally. During irradiating the Rb vapor, mixed with H₂, by two light beams for selective stepwise excitation, the Rb 8²S_1/2→5²P_3/2 direct fluorescence and the Rb 6²D_3/2→5²P_1/2 sensitized fluorescence have been measured as a function of H₂ gas pressure. The measurements yielded the cross-sections σ(8²S_1/2→6²D) and σ^*(8²S_1/2→6²D) of Rb 8²S_1/2→6²D excitation tranfer induced by collisions with 5²S_1/2 atom and H₂ molecules respectively. The results are discussed in detail.     

243—263nm S原子Rydberg态的(2+1)共振增强多光子电离

在243—263nm波长范围,测量了S⁺分质量激发谱,得到SO₂分子光解产生的S原子近50条(2+1)共振增强多光子电离谱线．除了来自S原子基态3p⁴³P_2,1,0直至n=10的Rydberg态³P,³D,³F的许多双光子跃迁谱线外,观察到若干新的¹P⁰,⁵S^关键词：     

多参考组态相互作用方法研究BS+离子的势能曲线和光谱性质

利用量子化学从头计算方法MRCI+Q在AVQZ级别上对BS⁺离子进行了研究. 通过计算得到了与BS⁺离解极限B⁺（¹S_g）+S（³P_g）和B⁺（¹S_g）+S（¹D）对应的5个Λ-S态,确认了BS⁺离子的基态为X³∏电子态,而第一激发态¹∑⁺的激发能T_e仅仅为564.53 cm^-1. 首次纳入的旋轨耦合效应（SOC）使得BS⁺的5个Λ-S态分裂成为9个Ω态,原有的两个离解极限分裂为B⁺（¹S₀）+S（³P₂）,B⁺（¹S₀）+S（³P₁）,B⁺（¹S₀）+（³P₁）以及B⁺（¹S₀）+S（¹D₂）. 在考虑自旋轨道耦合效应之后,Ω态的基态为X2态. 通过势能曲线（PECs）可以发现所得到的Λ-S态和Ω态均为束缚态,利用LEVEL8.0程序拟合得到了对应电子态的光谱常数,这些结果可以为实验和理论方面进一步研究BS⁺的光谱性质提供准确的电子结构信息. 关键词： 势能曲线 光谱参数 多参考组态相互作用方法 Q)')" href="#">Davidson修正(+Q)     

反应物NO的振动激发对反应C(3P)+NO(X2Π)→CO(X1Σ+)+N(2D)立体动力学性质的影响

采用准经典轨线方法研究碰撞能为0.23 eV时,反应物分子NO在不同初始振动态（v=0~3）下发生在两个电子态（²A″和²A'）势能面上反应C（³P）+NO（X²Π）→CO（X¹Σ⁺）+N（²D）的立体动力学性质。计算反应产物的转动角动量矢量分布（P（θ_r）和P（φ_r））以及微分散射截面（P₀₀（ω_t）,P₂₀（ω_t））。结果表明：反应物的振动激发对发生在²A'势能面上的反应立体动力学性质影响显著,而对发生在²A″势能面上的反应立体动力学性质影响较小,这可能与两个势能面的构型有关。在两个电子态势能面上发生的反应均受内平面反应机理支配。     

固体中稀土离子的能级位移和电子云扩大效应

本文计算了25个含Eu³⁺离子的晶体中由于晶场效应引起的Eu³⁺离子的⁵(D_J),⁷(F_J)能级的位移和⁵D,⁷F谱项能级劈裂的加宽,分析了电子云扩大效应引起的能级位移与实验测量值的关系,并给出这些晶体中电子云扩大效应大小的正确次序。 关键词：     

聚合型硼氢化物(BH3)n(n=1-3)的几何结构与光谱的研究

采用不同方法B3P86,B3LYP,MP2和LSDA,结合Dunning的相关一致基组cc-PVTZ,对聚合型硼氢化物(BH₃)_n(n=1-3)分子的可能几何构型进行优化计算,得出最稳定构型的几何参数、电子结构、振动频率和光谱等性质参数,并给出了最稳定结构的总能量(E_T),结合能(E_BT),平均结合能(E_av),电离势(E_IP),能隙(E_g),费米能级(E_F)等.结果表明:采用密度泛函DFT中的方法B3P86计算的能量最低,结构参数更接近文献值;三种硼氢化物分子基态都为1重态,电子态分别为¹A',¹A和¹A; BH₃分子的最稳定几何构型为平面三角形结构;B₂H₆为对称性乙烯式D_2h立体结构,H-B之间生成氢桥式三中心双电子键;B₃H₉为C_3ν立体结构,也生成氢桥式三中心双电子键,但三个氢桥三中心双电子键彼此隔离.最后分析了三种氢化物的红外和拉曼光谱、平均结合能、电离势、能隙和费米能级等特性,说明(BH₃)_n(n=1-3)三分子中B₂H₆最稳定,H-B桥键键长比端键更长,最强峰红外光谱强度最大. 关键词： 聚合型硼氢化物 几何构型 光谱     

一价铝离子能级结构的多通道量子亏损理论分析

利用多通道量子亏损理论(MQDT)对一价铝离子(AIII)的各受干扰序列:3sns ¹S₀,3snp ³P_0,1,2^O,¹P₁^O,3snd ¹D₂和3snf³F_2,3,4^O的能级结构进行理论分析。结果表明:前两个序列所受到的干扰较弱,后三个序列则受到了来自干扰态3p4s ¹P₁^O,3p^{2 1}D₂和3p3d³F_2,3,4^O的强烈干扰,而3snf ¹F₃^O序列则受到来自电离限上方干扰态的影响。利用获得的MQDT参数推算出3p3d ¹F₃^O干扰态位于电离限上方5613cm^-1处,这一结果与其他作者的预言相符合。 关键词：     

H+CH→H2+C（1D）反应的立体动力学研究

利用从头计算的对称性为1A′的势能面,用准经典轨线（QCT）方法在不同的碰撞能下研究了反应H+CH→H₂+C（¹D）的产物和反应物的矢量相关性质.在质心系下计算了四个极化微分反应截面.计算并讨论了描述k和j′夹角分布关系的P（θ_r）和描述k-k′-j′三者的二面角分布关系的P（（?）_r）.计算结果表明势能面上的深势阱和不同的碰撞能对产物分子H₂有重要影响.     

Ionization and dissociative ionization of methane molecules

A technique for mass-spectrometric investigation of the yield of positive ions produced by direct and electron-impact dissociative ionization of methane molecules is described, and respective experimental data are presented. Doubly charged C ₂ ⁺ , CH ₃ ²⁺ , and CH ₄ ²⁺ ions, as well as singly charged D ₂ ⁺ , CD ₃ ⁺ , and CD ₄ ⁺ ions, are detected in the mass spectrum of a methane molecule at electron energy U _e = 90 eV for the first time. From ionization efficiency curves, the ionization energy of the parent molecule and the appearance energy of fragment ions are determined. The ionization energy of the CH₄ molecule is found to be 12.62 ± 0.20 eV. Electron-molecular reactions that may take place when a low-energy electron beam interacts with a methane molecule are analyzed. The ionization process and the formation of methane molecule fragments are studied.     

Ionization of hydrogen and deuterium atoms in thermal energy collisions with state-selected Ne(3s 3 P 2,3 P 0) metastable atoms

High resolution energy spectra of electrons and ions resulting from thermal energy collisions of hydrogen and deuterium atoms with state-selected metastable Ne(Ne(3s ³ P ₂,³ P ₀) atoms are reported. The electron spectra for Ne(³ P ₂)+H(D) are very broad: The high energy part due to formation of NeH⁺ (NeD⁺) bound states (associative ionization), amounts to about 30% of the ionizing events, whereas the dominant part of the spectrum including a prominent low-energy peak is due to Penning ionization out of a strongly-attractive entrance potential curve. Comparison of the spectra with quantum mechanical fit calculations yields fairly accurate information on this potential, in particular its well depthD _e [Ne(³ P ₂)?H,D]= 2.0(1) eV. The spectra for Ne(³ P ₀)+H, D are comparatively narrow with much lower cross sections than the one for the Ne(³ P ₂) state. The corresponding entrance channel is a weakly bound van der Waals molecule with a well depth below 0.1 eV. A perturbation calculation of the Ne(3s)+H(1s) potential energy curves at large distances explains the observed difference between the Ne(³ P ₂)+H(D) and Ne(³ P ₀)+H(D) systems. Symmetry arguments are given that the major contribution to the Ne(³ P ₂)+H(D) spectra is due to the² Σ potential.     

Two-step excitation of Rb atoms on He nanodroplets

We present the first sequential laser excitation of atom-doped helium nanodroplets. Rubidium atoms on the surface of helium nanodroplets are selectively excited with a continuous wave laser to the 5²P_1/2 state so as not to desorb from the nanodroplets. From there they are excited by a laser pulse to the 5²D state; a laser-induced fluorescence (LIF) spectrum is recorded by monitoring the 6²P ?\rightarrow 5²S_1/2 emission. The LIF spectrum differs from that of the two-photon one-color direct excitation spectrum 5²D ?\leftarrow 5²S_1/2, indicating that the system does relax vibrationally during the lifetime of the 5²P_1/2 state. To model the LIF spectra we use calculated energy levels of the Rb atom as a function of its distance R from the center of the helium nanodroplet. The Franck-Condon factors of the resulting potential energy curves agree with the experimental spectra. In the future the 5²P_1/2 state can be used as a springboard to reach high-lying ²S and ²D states, and possibly create an artificial super-atom.     

Electron spectroscopy using excited atoms and photons IX. Penning ionization of CO2, CS2, COS,N2O,H2S,SO2, and NO2

The electron spectra resulting from thermal collisions of He* (predominantly 2³S) metastable atoms with the seven triatomic molecules, CO₂, COS, CS², N₂O H₂S, SO₂ and NO₂, are compared with their respective 584-Å photoelectron spectra using a transmission-corrected electron spectrometer. The normalised relative electronic-state transition probabilities for production of ionic states in Penning ionization and photoionization are reported together with energy shifts (ΔE values) for He*(2³S) Penning ionization. The cross-section for Penning ionization to lower states of NO₂⁺ is extremely low as has been observed in other open shell molecules such as NO and O₂.     

Spectrum diagnostics. The necessity for detailed non-LTE modeling of X-ray emission from dense plasmas

Except in the simplest of physical situations, broadband spectrum formation in dense optically thick plasmas is the result of a highly complex set of nonlinear phenomena. At NRL, we are developing models to investigate a number of the theoretical issues related to the interpretation of time integrated X-ray spectra. Many of the individual features of these spectra can be understood qualitatively and modeled quantitatively (see Ref. 3). However, a number of questions concerning the self-consistency of theoretical treatments of an entire spectrum remain. A few of these questions will be examined and discussed in this talk within the context of imploding plasmas.Spectrum formation at high ion densities will be described using an argon K-shell model containing atomic structure up to n = 10 in both hydrogen and helium-like ionization stages as well as lower excited states in the lithium-like system. Lyman series emission is computed along with three prominent satellite lines of the H- and He-L_α lines and He 1s²?1s2p³P intercombination line. Local Stark profiles are also computed and used for L_α, L_β, and L_γ lines of both the hydrogen and helium-like series. For the higher lying lines, which are strongly overlapped at high densities, collisional width estimates for Voigt profiles are used. The overlap of satellite, intercombination, and L_α resonance lines, on the other hand, occurs as the result of overlapping Stark and Voigt profiles.The influence of these different line profile assumptions on spectrum formation at high density will be discussed in terms of the problems of self-consistently inferring plasma conditions during emission, such as temperature, density, and plasma ionization state. These are usually inhomogeneous in both space and time. However, some recent progress at NRL enables us to theoretically address these problems. We will discuss them within the context of post-processing the temperature and density profiles that are predicted by hydrodynamics calculations of imploded, Argon/DT filled, glass microballoons.     

Synchrotron radiation VUV double photoionization of CHF2Cl

VUV double photoionization of CHF₂Cl in an energy region 32–40 eV was investigated with photoionization mass spectroscopy by using synchrotron radiation. The double ionization energy of CHF₂Cl and appearance energies for its main fragment dications (CHCl²⁺, CF₂²⁺ and CHFCl²⁺), were determined with photoionization efficiency spectroscopy for the first time. The single point energies of CHF₂Cl and its parent dication (CHF₂Cl²⁺) were calculated using Gaussian 03 program and density functional theory (DFT and B3LYP functional). The vertical double ionization energy of CHF₂Cl was predicted by using B3LYP method and empirical equation. According to our research results, the experimental double ionization energy of CHF₂Cl is in good agreement with the theoretically calculated vertical double ionization energy. The mechanism of double photoionization of CHF₂Cl was discussed based on the comparison of our experimental results with those predicted theoretically.     

Multiphoton ionization spectra in lithium vapour

The two-photon absorption spectrum to high-lying states of Li vapour has been obtained using ion-cell detection. ²S states are observed to n = 32 and the ²D series to n = 49. Simple heating techniques circumvented the problem of absorption by the blue-green band system of Li₂ which overlaps the series limit at 4600 Å. The order of the ionization process was examined and found to vary as the square of the laser intensity for two-photon transitions. A conflict with data obtained with a space-charge-limited diode is examined and possible ionization mechanisms are discussed.     

Molecular ionization of cyclohexanone in femtosecond laser fields: An application of ADK theory

The mechanisms of ionization and dissociation of cyclohexanone (C₆H₁₀O) in a 90 fs, 788 nm linearly polarized laser field ranging from 10¹³ to 10¹⁴ W/cm² by a time-of-flight mass spectrometer (TOF-MS) have been investigated. The ion yields as a function of laser intensity have been measured experimentally. By comparison with the Ammosov-Delone-Krainov (ADK) theory based on a hydrogen-like model, the ionization mechanism of cyclohexanone in this intense femtosecond laser field has been understood. Considering the importance of molecular nuclear motions, we propose that the Franck-Condon (F-C) factor can provide the excess vibrational energy in the molecular ion. This energy is required for the decomposition of the molecular ion which finally results in the observed mass spectrum.     

Similarities between 2D and 3D convection for large Prandtl number

Using direct numerical simulations of Rayleigh–Bénard convection (RBC), we perform a comparative study of the spectra and fluxes of energy and entropy, and the scaling of large-scale quantities for large and infinite Prandtl numbers in two (2D) and three (3D) dimensions. We observe close similarities between the 2D and 3D RBC, in particular, the kinetic energy spectrum E_u(k)～k^?13/3, and the entropy spectrum exhibits a dual branch with a dominant k^?2 spectrum. We showed that the dominant Fourier modes in 2D and 3D flows are very close. Consequently, the 3D RBC is quasi-two-dimensional, which is the reason for the similarities between the 2D and 3D RBC for large and infinite Prandtl numbers.     

The reactions N14(n, α)B11 and N14(n,t)C12 observed with a gridded ionization chamber

The cross sections for the reactions N¹⁴(n, α)B¹¹ and N¹⁴(n, t)C¹² have been measured in the neutron energy range 4.0 to 6.4 MeV and at 2.5 MeV. Mono-energetic neutrons were produced in the D(d, n) He³ reaction using a gas target. The (n, α) and (n, t) disintegrations were detected in a gridded ionization chamber filled with an argonnitrogen mixture. The response of the chamber under different operation conditions is described. The excitation functions, measured with a neutron energy resolution of 40 to 50 keV, are given for theα ₀ group from the N¹⁴(n,α)B¹¹ reaction over the entire neutron energy range and for theα ₁ group and the t₀ group from N¹⁴(n, t) C¹² for neutron energies above 4.3 and 5.6 MeV, respectively.