量子Monte Carlo处理激发态

提出了用于电子激发态的剩余函数变分量子ＭｏｎｔｅＣａｒｌｏ（ＳＦＶＭＣ）方法,已经证明：若激发态的初始波函数与基态的初始波函数属于对称性不同的不可约表示时,该激发态的ＳＦＶＭＣ方法与基态的ＳＦＶＭＣ方法完全相同;若激发态的初始波函数与基态的初始波函数有相同的对称性时,只要对激发态的初始波函数作正交性修正,则其态的ＳＦＶＭＣ方法亦可推到该激发态的情况。文章导出了这第二类激发态的ＳＦＶＭＣ方法的详细计     

飞秒时间分辨的光电子影像对3-甲基吡啶分子超快动力学研究(英文)

利用飞秒时间分辨的光电子影像技术结合时间分辨的质谱技术,研究了3-甲基吡啶分子激发态的超快过程.实时观察到了3-甲基吡啶分子S2态向S1态高振动能级的超快内转换过程,该内转换的时间大约为910fs.二次布居的S1态主要通过内转换衰减到基态S0,该内转换的时间尺度为2.77 ps.光电子能谱分布和光电子角分布显示,S2态和S1态在电离的过程中跟3p里德堡态发生偶然共振.本次实验中还用400 nm两个光子吸收的方法布居了3-甲基吡啶的3s里德堡态.研究表明,3s里德堡态的寿命为62 fs,并主要通过内转换快速衰减到基态.     

PH2^+基态及低激发态的构型优化及光谱性质理论研究

本文报道了PH2^+的一组新的ab initio计算结果。给出了PH2^+的基态(X^1A1)及几个低激发态的电子结构和几何构型。这些态的稳定构型都是在MRSD CI水平上优化得到的。在此基础上, 确定了基态到这些低激发态的跃迁能和部分跃迁的振子强度和辐射寿命。     

HCB和HCB-的激发态光谱与态-态转化的理论研究

HCB是最简单的有机硼化合物，理论上已有少量研究，报导了部分激发态及其谐振动频率．关于HCB-及其异构体HBC-的研究未见报导．本文采用精确的量子化学计算方法，对它们的激发态性质、光谱和态一态转化进行了系统的研究，为实验上对这些物质的研究提供了一些有用的信息．计算采用极化的三Zeta基组（TZP）进行基态和激发态的构型优化与振动性质调查各电子态相关能估算应用基于多组态自洽场分子轨道的一级组态相互作用（FOCI／MCSCF）方法．计算过程中，考虑到对称性破裂（symmetrybrealling）的影响同，对存在对称性破裂的体系采用…     

HeLi^n^+(n=0, 1)簇合物的稳定性和垂直激发态光谱

本文用ab initio研究了簇合物HeLi^n^+(n=0, 1)的几何构型和成键性质。在MP2(FULL)/6-31G**, 水平优化所得LeLi^+的平衡键长为0.2062nm, 与实验值0.205nm十分吻合。比较了HeLi^+(X^1∑^+和a^3∑^+), HeLi(X^2∑^+和a^4II)以及HLi(X^1∑^+)的稳定性, 计算了HeLi^+基态的相关能, 势能曲线和垂直激发态光谱。计算采用了6-31G**, 6-311G**,6-311G(2df, 2pd), 6-311G(3df, 2pd)和6-311+G(3df, 2pd)基组; 采用的方法包括MP2(FULL), MP4, MCSCF, MRSDCI, CCD和ST4CCD。计算表明, 同价HeLi^n^+中激发态的离解能均远比基态的大, 其中HeLi^+(a^3∑^+)的离解能最高(60.49kj/mol),说明激发态是稳定束缚态。HeLi^+基态比等电子体HLi分子基态的稳定性小得多。HeLi^+由A^1∑^+到B^1II的垂直跃迁(3σ→1π)振子强度较大而垂直跃迁能较小。     

飞秒时间分辨的光电子影像对3-甲基吡啶分子超快动力学研究

利用飞秒时间分辨的光电子影像技术结合时间分辨的质谱技术,研究了3-甲基吡啶分子激发态的超快过程. 实时观察到了3-甲基吡啶分子S₂态向S₁态高振动能级的超快内转换过程,该内转换的时间大约为910fs. 二次布居的S₁态主要通过内转换衰减到基态S₀,该内转换的时间尺度为2.77 ps. 光电子能谱分布和光电子角分布显示,S₂态和S₁态在电离的过程中跟3p里德堡态发生偶然共振. 本次实验中还用400 nm两个光子吸收的方法布居了3-甲基吡啶的3s 里德堡态. 研究表明,3s 里德堡态的寿命为62 fs,并主要通过内转换快速衰减到基态.     

S3分子的结构与最可几解离过程理论研究

用量子化学从头算方法,计算得到了S3分子优化的几何结构(基态和几个低激发态);研究了其在C2v与Cs群对称性下的解离过程,给出两种群对称性下基态和激发态的势能曲面及等高投影图;在两种群对称性下均得到在相应势能曲面上的优化的解离路径.     

C2F51分子C—I键解离的自旋-轨道从头算研究

采用考虑相对论效应的6—311G^＊＊全电子基组与多参考微扰理论,计算了该分子的包含自旋-轨道耦合效应的垂直激发能和基态、激发态C—I键解离势能曲线．理论计算发现,势能曲线3^3A＂与1^1A＂,2^1A＇出现交叉,交叉区域在C—I键长为0．241nm附近;基态1^A＇到激发态3^3A＂（^3Q0）的垂直激发能为4．658eV,与实验值4．662eV非常吻合．讨论了C2F5I分子作为碘激光介质的可行性．     

石墨烯条带的电子结构与性质:电场及长度效应

在密度泛函理论(DFT)和含时密度泛函理论(TDDFT)的基础上对宽度上含有8个zigzag链的石墨烯条带(8-ZGNR)的基态和激发态的性质进行了理论研究,着重考察了条带长度及电场的影响.B3LYP杂化泛函的计算结果显示:在基态上,8-ZGNR的最低能量态并不具有磁性,随着长度的增加,才会显示出反铁磁的性质.静电场的加入使8-ZGNR显示出反铁磁性和半金属性.在激发态上,诱导电子会随着外激光脉冲的变化而发生移动和变化,但是相比而言,α自旋电子更容易被激发而产生较明显的诱导电子密度,而β自旋电子则更容易脱离外激光场的控制而产生非绝热现象.     

NiCO电子能级的自旋非限制X_α—SW法计算

利用自旋非限制X_α-SW法计算了不同状态的NiCO电子能级。结果表明基态是~1∑~+态而不是~3△态。和~3△态相比,~1∑~+态有较强的σ给予作用和π反馈作用。和自由CO配体比较,CO配体的5σ能级位移1π的要大。和实验一致,基态~1∑~+是反磁性的。我们还计算了基态~1∑~+的电荷密度、轨道电离能和跃迁能。     

Molecular frame photoelectron angular distributions for H2 ionization by single and trains of attosecond XUV laser pulses

The delayed autoionization of H₂ doubly excited states into channels of different inversion symmetry gerade and ungerade is investigated by using pulses of attosecond duration (isolated or packed in trains), linearly polarized along the molecular axis. It has been shown in previous work, by using XUV laser pulses with durations of 4 fs or longer, that the molecular frame photoelectron angular distributions (MFPAD) associated with the dissociative channel H⁺ + H(n?) are not symmetric with respect to the inversion center of the molecule. In contrast, the MFPADs become symmetric for shorter fs pulses. Here we show that, although this is still the case for pulses of attosecond duration, the combination of two of these pulses with a controlled time delay may still lead to asymmetric MFPADs. From the analysis of the time evolution of the calculated MFPADs, we propose a way to elucidate autoionization lifetimes of molecular resonant states. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2462–2471, 2010     

N 1s photoelectron angular distributions from fixed-in-space NO2 molecules: stereodynamics and symmetry considerations

Angular distributions of N 1s photoelectrons from fixed-in-space NO(2) molecules have been measured over the energy region of shape resonance and above. A multiple-coincidence velocity-map imaging technique for observation of molecular frame photoelectron angular distributions (MF-PADs) has been extended to nonlinear molecular targets. Density functional theory calculations have also been conducted to elucidate the photoionization dynamics and shape resonance in the N 1s photoionization of NO(2). Results show that the N 1s MF-PADs exhibit strong shape variation as a function of both photoelectron kinetic energy and symmetries of final states, whereas asymmetry parameters of laboratory frame PADs show a local minimum around the shape resonance region and increase monotonically as the photon energy increases. Over the shape resonance, the spatial shape of the photoelectron wave function with b(2)-symmetry closely resembles that of 5b(2)(?) unoccupied molecular orbital of NO(2), although the MF-PAD pattern for b(2)-symmetry does not correspond directly to the 5b(2)(?) orbital shape. At higher kinetic energy of 90 eV, MF-PADs become less structured, but still show a significant dependence on the symmetry of final states.     

Quantum control of molecular orientation by two-color laser fields

We demonstrate molecular orientation by using phase-controlled two-color omega+2omega laser pulses with an intensity of 1.0x10(12) W/cm(2) and a pulse duration of 130 fs. The orientation of three iodine-containing molecules (IBr, CH(3)I, and C(3)H(5)I) was monitored by the directional asymmetries of the photofragment angular distribution in dissociative ionization. In all three molecules, the directional asymmetry showed an oscillating behavior dependent on the relative phase difference between omega and 2omega pulses. The phase dependence of the directional asymmetry observed in iodine ions and counterpart ions were out of phase with each other. This result shows that a phase-controlled omega+2omega optical field discriminates between parallel and antiparallel configurations of aligned molecules that have a permanent dipole. This method performed well because (1) molecular orientation can be achieved by all-optical fields; (2) the direction of orientation is easily switched by changing the sign of the quantum interference; and (3) this method is free from any resonance constraint and thus can be applied to any molecule.     

O1s photoionization dynamics in oriented NO2

We have performed extensive density functional theory (DFT) calculations, partial cross sections, dipole prepared continuum orbitals, dipole amplitudes and phase shifts, asymmetry parameters β, and molecular frame photoelectron angular distributions, to elucidate the O1s photoionization dynamics of NO(2) molecule with emphasis on the shape resonances in the O1s ionization continuum. In the shape resonance region, the β parameters and photoelectron angular distributions have been compared with our experimental results. Fairly good agreement between the theory and experiment has confirmed that the DFT level calculations can well describe the photoionization dynamics of the simple molecule such as NO(2). Interference due to equivalent atom photoionization is theoretically considered, and the possibility of detection of the effect in the two degenerate channels with different combinations of light polarization and photoemission direction is discussed.     

Laser-induced alignment and anti-alignment of rotationally excited molecules

We numerically investigate the post-pulse alignment of rotationally excited diatomic molecules upon nonresonant interaction with a linearly polarized laser pulse. In addition to the simulations, we develop a simple model which qualitatively describes the shape and amplitude of post-pulse alignment induced by a laser pulse of moderate power density. In our treatment we take into account that molecules in rotationally excited states can interact with a laser pulse not only by absorbing energy but also by stimulated emission. The extent to which these processes are present in the interaction depends, on the one hand, on the directionality of the molecular angular momentum (given by the M quantum number), and on the other hand on the ratio of transition frequencies and pulse duration (determined by the J number). A rotational wave packet created by a strong pulse from an initially pure state contains a broad range of rotational levels, over which the character of the interaction can change from non-adiabatic to adiabatic. Depending on the laser pulse duration and amplitude, the transition from the non-adiabatic to the adiabatic limit proceeds through a region with dominant rotational heating, or alignment, for short pulses and a large region with rotational cooling, and correspondingly preferred anti-alignment, for longer pulses.     

Photoelectron angular distribution in valence shell ionization of heteroaromatic molecules studied by the continuum multiple scattering xalpha method

Photoelectron angular distributions are calculated for the valence shell ionization of heteroaromatic molecules of pyridine, pyrazine, pyrimidine, pyrrole, and furan by the continuum multiple scattering Xalpha method. The asymmetry parameters exhibit strong energy dependences in ionization from pi orbitals but are almost invariant in ionization from sigma orbitals, in good agreement with experimental results. The asymmetry parameters in ionization from nonbonding orbitals appear generally higher than those in ionization from bonding orbitals. These features are interpreted in terms of the Coulomb phase and photoelectron angular distribution in the molecular frame.     

Valence and inner-valence shell dissociative photoionization of CO in the 26-33 eV range. II. Molecular-frame and recoil-frame photoelectron angular distributions

Experimental and theoretical results for molecular-frame photoemission are presented for inner-valence shell photoionization of the CO molecule induced by linearly and circularly polarized light. The experimental recoil frame photoelectron angular distributions (RFPADs) obtained from dissociative photoionization measurements where the velocities of the ionic fragment and photoelectron were detected in coincidence, are compared to RFPADs computed using the multichannel Schwinger configuration interaction method. The formalism for including a finite lifetime of the predissociative ion state is presented for the case of general elliptically polarized light, to obtain the RFPAD rather than the molecular frame photoelectron angular distribution (MFPAD), which would be obtained with the assumption of instantaneous dissociation. We have considered photoionization of CO for the photon energies of 26.0 eV, 29.5 eV, and 32.5 eV. A comparison of experimental and theoretical RFPADs allows us to identify the ionic states detected in the experimental studies. In addition to previously identified states, we found evidence for the 2 (2)Δ state with an ionization potential of 25.3 eV and (2)Σ(+) states with ionization potentials near 32.5 eV. A comparison of the experimental and theoretical RFPADs permits us to estimate predissociative lifetimes of 0.25-1 ps for some of the ion states. Consideration of the MFPADs of a series of (2)Π ion states indicates the importance of inter-channel coupling at low photoelectron kinetic energy and the limitations of a single-channel analysis based on the corresponding Dyson orbitals.     

Angular distributions in the photoelectron spectroscopy of furan,thiophene, and pyrrole

The photoelectron angular distributions of furan, thiophene, and pyrrole are reported. The trends in the value of the asymmetry parameter β and in the shapes and positions of bands in the spectra are used to assign the peaks that correspond to ionization from the π orbitals in these molecules.     

Probing Rapidly‐Ionizing Super‐Atom Molecular Orbitals in C60: A Computational and Femtosecond Photoelectron Spectroscopy Study

Super‐atom molecular orbitals (SAMOs) are diffuse hydrogen‐like orbitals defined by the shallow potential at the centre of hollow molecules such as fullerenes. The SAMO excited states differ from the Rydberg states by the significant electronic density present inside the carbon cage. We provide a detailed computational study of SAMO and Rydberg states and an experimental characterization of SAMO excited electronic states for gas‐phase C₆₀ molecules by photoelectron spectroscopy. A large band of 500 excited states was computed using time‐dependent density functional theory. We show that due to their diffuse character, the photoionization widths of the SAMO and Rydberg states are orders of magnitude larger than those of the isoenergetic non‐SAMO excited states. Moreover, in the range of kinetic energies experimentally measured, only the SAMO states photoionize significantly on the timescale of the femtosecond laser experiments. Single photon ionization of the SAMO states dominates the photoelectron spectrum for relatively low laser intensities. The computed photoelectron spectra and photoelectron angular distributions are in good agreement with the experimental results.     

Electronic states of thiophenyl and furanyl radicals and dissociation energy of thiophene via photoelectron imaging of negative ions

We report photoelectron images and spectra of deprotonated thiophene, C(4)H(3)S(-), obtained at 266, 355, and 390 nm. Photodetachment of the α isomer of the anion is observed, and the photoelectron bands are assigned to the ground X(2)A(') (σ) and excited A(2)A(") and B(2)A(") (π) states of the thiophenyl radical. The photoelectron angular distributions are consistent with photodetachment from the respective in-plane (σ) and out-of-plane (π(?)) orbitals. The adiabatic electron affinity of α-(●)C(4)H(3)S is determined to be 2.05 ± 0.08 eV, while the B(2)A(") term energy is estimated at 1.6 ± 0.1 eV. Using the measured electron affinity and the electron affinity/acidity thermodynamic cycle, the C-H(α) bond dissociation energy of thiophene is calculated as DH(298)(H(α)-C(4)H(3)S) = 115 ± 3 kcal/mol. Comparison of this value to other, previously reported C-H bond dissociation energies, in particular for benzene and furan, sheds light of the relative thermodynamic stabilities of the corresponding radicals. In addition, the 266 nm photoelectron image and spectrum of the furanide anion, C(4)H(3)O(-), reveal a previously unobserved vibrationally resolved band, assigned to the B(2)A(") excited state of the furanyl radical, (●)C(4)H(3)O. The observed band origin corresponds to a 2.53 ± 0.01 eV B(2)A(") term energy, while the resolved vibrational progression (853 ± 42 cm(-1)) is assigned to an in-plane ring mode of α-(●)C(4)H(3)O (B(2)A(")).