激发态铷分子的光离解

研究了Rb(52P3/2)+Rb(5S)+nhν→Rb(72DJ)+Rb(5S)+(n-1)hν过程, 激光频率ν调到Rb7D3/2→5P3/2跃迁谱线的两翼20-100 cm-1, 测量了精细结构谱线强度分支比I(7D3/2→5P1/2)/I(7D5/2→5P3/2). 实验表明, 原子相互作用势和非绝热效应在离解动力学中起关键作用.     

Kinetics of the Structural Transition to a Highly Excited State

It is demonstrated that in a crystal that undergoes a martensitic transition stimulated by an external force pacemakers arising in inhomogeneous regions of the medium are sources of forming an incommensurable lattice structure.     

7-(3,6-二硝基-N-p-乙烯基苯基咔唑)香豆素分子的光谱和激发态的密度泛函理论研究

采用密度泛函理论(DFT)对7-(3,6-二硝基-N-p-乙烯基苯基咔唑)香豆素分子做理论研究。用B3LYP/6-31G(d,p)对其几何结构进行优化,得到其最稳定构型及能量。在优化结构的基础上,对其进行频率分析得到了分子的红外光谱和拉曼光谱,并对谱线中的各峰值做了具体指认,同时也得到了分子的最高占据轨道(HOMO)和最低空轨道(LUMO)能隙为2.150eV。利用含时密度泛函理论(TDDFT)对该分子的激发态进行计算,得到最低十个跃迁允许的单激发态。对前线分子轨道最高占据轨道和最低空轨道分析得到,C-C原子之间形成了离域π键。研究结果表明:7-(3,6-二硝基-N-p-乙烯基苯基咔唑)香豆素是一种良好的有机半导体材料,并具有很好的发光性能。     

Experimental Determination of Ground and Excited State Dipole Moments of N,N-Bis (2, 5-di-tert-butylphenyl)-3, 4:9, 10-perylenebis (dicarboximide) (DBPI) A Photostable Laser Dye

In the present work, the absorption, emission spectra and dipole moments(μ_g, μ_e) of N, N-bis (2, 5-di-tert-butylphenyl)-3, 4:9, 10- perylenebis (dicarboximide) (DBPI) have been studied in solvents of various polarities at room temperature. Using the methods of solvatochromism, the difference between the first excited singlet state (μ_e) and ground state (μ_g) dipole moments was estimated from Lippert – Mataga,, Bakhshiev, Kawski – Chamma – Viallet equations. The change in dipole moment (Δμ) was also calculated using the variation of the Stokes shift with microscopic solvent polarity parameter (E _T ^N ). It was observed that the value of excited singlet state dipole moment is higher (3.53 Debye) than the ground state one (1.92Debye), showing that the excited state of DBPI is more polar than the ground state.     

Double-Modulation Submillimeter-Wave Spectroscopy of HOC(+) in the nu(2) Excited Vibrational State

The submillimeter-wave rotational transitions of HOC(+) in the nu(2) excited state are first detected using the double-modulation method, and the precise transition frequencies and the much improved molecular constants are obtained. The measurements of the ground state HOC(+) and DOC(+) submillimeter-wave lines are extended up to the 840-GHz region. It is found that the higher order centrifugal distortion constant, H, is necessary to fit the observed transition frequencies to the experimental accuracy. Copyright 2000 Academic Press.     

Spectral Properties of Amphiflavins in Polymer Matrices

The parameters characterizing the absorption, fluorescence and phosphorescence of 10-dodecylisoalloxazine (DIA), 10-octadecylisoalloxazine (OIA) 3-methyl-10-dodecylisoalloxazine (MDIA) embedded into polymeric matrices (polystyrene – PS, polymethacrylate methyl – PMM and poly(vinyl alcohol) – PVA) were studied. It was found that both the polarity of microenvironment and its structure influenced the changes of the spectral properties of the examined amphiflavins.     

Low-Frequency Internal Friction Study on the Structural Changes in Polymer Melts

With the help of the low-frequency internal friction method, we investigate the structural properties of polymer melts, such as amorphous polystyrene （PS）, poly（methyl methacrylate） （PMMA）, and semi-crystalline poly（ethylene oxide） （PEO）. An obvious peak of relaxation type is found in each of the internal friction curves. The peak temperature Tp follows the relation Tp ≈ （1.15- 1.18）Tg for PS and PMMA melts, while it follows Tp ≈ 1.22Tm for PEO melt, with Tg being the glass transition temperature and Tm the melting temperature. Based on the analysis of the features of this peak, it is found that this peak is related to the liquid-liquid transition temperature Tn of polymer melts. Mechanism of the liquid-liquid transition is suggested to be thermally-activated collective relaxation through cooperation. This finding may be helpful to understand the structural changes in polymer melts. In addition, the internal friction technique proves to be effective in studying dynamics in polymer melts.     

Theoretical Studies on the Ground State and Excited State of 2,70-(Ethylene)-bis-8-hydroxyquinoline

采用DFT/B3LYP和HF方法优化了2,70-(乙烯基)-二-8-羟基喹啉的构型,计算了该化合物的电子亲合势、电离势,利用ZINDO半经验方法和含时密度泛函方法(TD-DFT)计算了吸收光谱的数值,用CIS方法优化了第一激发单态并在此基础上计算了发射光谱,当考虑溶剂化效应后,实验光谱与计算光谱符合得相当好. 通过分析能量与光谱数值,该化合物的电子传输能力强于8-羟基喹啉,吸收光谱和发射光谱发生红移. 通过分子内重组能的计算,三-2,70-(乙烯基)-二-8-羟基喹啉铝（Albiq3）的电子传输性能比三-8-羟基喹啉铝的差,比较两配合物的发射光谱,Albiq3的最大发射波长红移.     

Ground and Singlet Excited State Pyridinic Protonation of N9-Methylbetacarboline in Water-N,N-Dimethylformamide Mixtures

The ground and the singlet excited state pyridinic protonation of 9-methyl-9H-pyrido[3,4-b]indole, MBC, in water-N,N-dimethylformamide mixtures has been studied by absorption, steady state and time resolved fluorescence measurements. These proton transfer reactions elapse by a stepwise mechanism modulated by different hydrogen bonded adducts and exciplexes formed by water molecules and the pyridinic nitrogen atom of the MBC. Based in the present and previous studies, a general mechanistic Scheme for the ground and the singlet excited state MBC pyridinic protonation has been proposed. Accordingly, in the ground state, upon increasing the water proportion of the water-N,N-dimethylformamide mixtures, a hydrogen bonded complex, HBC, its hydrogen bonded proton transfer complex, PTC, a pre-cationic complex, PC, and the cation, C, are progressively formed. In the excited state, MBC, HBC and PC behave as independent fluorophores. Excited state cations, C*, are mainly formed by direct excitation of the ground state cations and, in minor proportion, by the excited state reaction of the PTC^* through the CL^* exciplex.     

Excited State Absorption Study in Hematoporphyrin IX

We present the study of the excited state absorption of Hematoporphyrin IX dissolved in dimethyl sulfoxide. All measurements were carried out using open aperture Z-scan and white-light continuum pump-probe with picosecond pulses to avoid triplet excited state absorption. Without the latter contribution, the results obtained with both techniques show a transition to a high singlet excited state. The vibronic progression of the Q-band is observed due to photobleaching of the ground state. In addition, we show that the excited state presents reverse saturable absorption for most of the spectral range studied. A long relaxation component of the first singlet excited state was evidenced with the pump-probe experiment. This result is in agreement with fluorescence lifetime and fluorescence quantum yield measurements. In order to elucidate the origin of the nonlinear effects, we used a three-level energy diagram to describe the principal singlet-singlet transitions.     

Excited State Intramolecular Proton Transfer in O-Tosylaminobenzaldehyde

Excited state intramolecular proton transfer (ESIPT) in o-tosylaminobenzaldehyde has been investigated. According to quantum-chemical calculations ESIPT in o-tosylaminobenzaldehyde is barrierless. Product of ESIPT undergoes efficient nonradiative deactivation caused by internal rotation of C(H)OH-group. The solvent orientational relaxation in anionic form of o-tosylaminobenzaldehyde was detected. The mechanism of anionic form fluorescence quenching at the addition of the base in a protic solvent is proposed. It consists in the intermolecular proton transfer from the protonated base to oxygen atom of aldehyde group followed by the internal rotation of C(H)OH-group.     

抛物量子线中极化子的激发态性质

研究抛物型量子线中极化子激发态的性质。采用线性组合算符法和Pekar变分法,导出了抛物量子线中强耦合和弱耦合两种情况下极化子的基态能量、第一内部激发能量、激发能和振动频率随量子线的约束强度的变化关系。数值计算结果表明:抛物型量子线中极化子的基态能量、第一内部激发能量、激发能和振动频率都随量子线约束强度的增强而增大,体现了量子线受限强度越大,相应的极化子的能量也越大。     

High-lying excited states in ~(10)Be from the ~9Be(~9Be,~(10)Be)~8Be reaction

A transfer-reaction experiment of ~9Be(~9Be,~(10)Be)~8Be was performed at a beam energy of 45 Me V.Excited states in ~(10)Be up to 18.80 Me V are produced using missing mass and invariant mass methods.Most of the observed high-lying resonant states,reconstructed from theα+~6He and t+~7Li decay channels,agree with the previously reported results.In addition,two new resonances at 15.6 and 18.8 Me V are identified from the present measurement.The 18.55 Me V state is found to decay into both the t + ~7Lig:s: and t + ~7Li?(0.478 MeV) channels, with a relative branching ratio of 0:93 ± 0:33. Further theoretical investigations are encouraged to interpret this new information on cluster structure in neutron-rich light nuclei.     

Role of Mode-mode Coupling in Short-time Excited State Decay

Master equation of a relevant electronic and vibrational system is derived for a special diabatic basis corresponding to vertical processes. It is shown that bath modes contribute dynamically to the inter-state coupling only at short times. For long times the bath-induced inter-state coupling is static and increases with the contribution of bath modes to the Stokes shift and to the Herzberg-Teller correction of the excited state. Simultaneously, the time evolution of excited state population is studied numerically for the system consisting of two electronic levels interacting with two vibrational modes, coupled to a heat bath. A mutual coupling of the vibrational modes in the excited state is taken into account (Duschinsky effect). Excited state population relaxes faster if interacting vibrational mode dissipates its energy via vibrational mode of a smaller eigenfrequency. Fast component of excited state depopulation cannot be achieved via coherent mode-mode coupling, if the second mode is not directly coupled to the electronic inter-state transition.     

Lifetime of a Nuclear Excited State in Cascade Decay

It is shown that the lifetime of a nuclear excited state in the region of femtoseconds could be accurately measured by a precision measurement facility of a flat crystal spectrometer, if the angular correlation of two successive γ-rays in cascade decay is taken into account in the Doppler shift attenuation method.     

分子内质子转移分子2-(2′-羟基苯基)间氮杂氧茚的光学非线性的研究

报道了在调Ｑ的Ｎｄ∶ＹＡＧ激光器泵浦下用Ｚ扫描技术对具有分子内质子转移（ＥＳＩＰＴ）特性的分子２（２′羟基苯基）间氮杂氧茚（ＨＢＯ）的光学非线性的研究。结果表明：对１．０６μｍ的光，ＨＢＯ无非线性吸收，其三阶非线性极化率不随入射光强而变；而在０．５３μｍ的激光作用下，ＨＢＯ表现出显著的双光子吸收，其双光子吸收系数随泵浦光强增强而减小，而其三阶非线性极化率实部则随泵浦光强的增强而增大。在建立双光子泵浦产生激发态分子内质子转移动态模型的基础上，通过理论计算很好地解释了实验现象     

甲醇/TiO2(110)界面激发态的表征

用光电子能谱的方法研究了甲醇/TiO₂(110)界面的电子结构．在激发波长为400 nm的双光子光电子能谱(2PPE)中,探测到了一个末态能量在费米能级以上5.5 eV的共振信号．之前的研究[Chem. Sci. 1, 575 (2010)]表明,这个共振信号与甲醇在5配位的钛离子(Ti_5c)上的光催化解离相关．双光子光电子能谱同时携带初态和中间态的信息．为此设计了一个调谐激发光波长的2PPE实验以及一个单光子光电子能谱(1PPE)和2PPE对比的实验,结果一致表明这个共振信号来自于未占据的中间态,也就是激发态．能带色散关系测量表明这个激发态是局域的．时间分辨2PPE测得这个激发态的寿命是24 fs．     

1-羟基蒽醌的分子内质子转移动力学

利用飞秒瞬态吸收光谱结合量化计算研究了1-羟基蒽醌在溶剂中的激发态分子内质子转移动力学. 分子受到400 nm光激发后的瞬态吸收谱呈现出激发态吸收和受激辐射两个光谱带. 受激辐射信号较激发态吸收信号滞后出现,由此确定质子转移时间是32 fs. 量化计算表明分子在沿质子转移路径衰变时,分子轨道和能级次序发生了反转,形成锥形交叉. 在质子转移之后,经锥形交叉布居的电子态发生内转换和分子间能量弛豫,时间分别是200 fs和16 ps. 基态回复时间是300 ps. 通过实验和理论研究,证实存在两个质子转移路径,其中主要的衰变路径保持了原来轨道的性质.     

Excited states of 10B from the 6Li(α, γ) and 9Be(p, γ) reactions

Excitation functions for the (α, γ) and (p, γ) reactions leading to ¹⁰B have been measured at θ = 0° in the energy range from E_x = 6.7 to 7.6 MeV. Two resonances corresponding to levels at 6.88 and 7.44 MeV are observed. Branching ratios extracted from γ-ray spectra are the same in both reactions for the 6.88 MeV (1^?, T = 0 + 1) level, but different at 7.44 MeV. The T = 0 + 1 level at 7.44 MeV (Γ = 90±10keV) is assigned 2^? or 2⁺ from its strong branch to the 3⁺ ground state. We find no evidence for a second isospin mixed 1^? state.