Vibration-assisted coherent excitation energy transfer in a detuned dimer

The important role of high-energy intramolecular vibrational modes for excitation energy transfer in the detuned photosynthetic systems is studied. Based on a basic dimer model which consists of two two-level systems(pigments)coupled to high-energy vibrational modes, we find that the high-energy intramolecular vibrational modes can enhance the energy transfer with new coherent transfer channels being opened when the phonon energy matches the detuning between the two pigments. As a result, the energy can be effectively transferred into the acceptor. The effective Hamiltonian is obtained to reveal the strong coherent energy exchange among the donor, the acceptor, and the high-energy intramolecular.A semi-classical explanation of the phonon-assisted mechanism is also shown.     

Light absorption and excitation energy transfer calculations in primitive photosynthetic bacteria

In photosynthetic organisms, light energy is converted into chemical energy through the light absorption and excitation energy transfer (EET) processes. These processes start in light-harvesting complexes, which contain special photosynthetic pigments. The exploration of unique mechanisms in light-harvesting complexes is directly related to studies, such as artificial photosynthesis or biosignatures in astrobiology. We examined, through ab initio calculations, the light absorption and EET processes using cluster models of light-harvesting complexes in purple bacteria (LH2). We evaluated absorption spectra and energy transfer rates using the LH2 monomer and dimer models to reproduce experimental results. After the calibration tests, a LH2 aggregation model, composed of 7 or 19 LH2s aligned in triangle lattice, was examined. We found that the light absorption is red shifted and the energy transfer becomes faster as the system size increases. We also found that EET is accelerated by exchanging the central pigments to lower energy excited pigments. As an astrobiological application, we calculated light absorptions efficiencies of the LH2 in different photoenvironments.     

Triplet-triplet transfer of electronic energy upon nonequilibrium vibrational excitation of triplet molecules

The specific features of the triplet-triplet (T-T) transfer of electronic excitation energy in a gas phase upon nonequilibrium vibrational excitation of the triplet molecules of a donor were studied for an anthraquinone-diacetyl donor-acceptor pair using the time-resolved slow fluoresence of anthraquinone and sensitized phosphorescence of diacetyl. It is shown that in the gas phase, which allows regular control of the number of collisions, competition between the processes of T-T transfer and intermolecular vibrational relaxation is observed for nanosecond time resolution. The T-T transfer rate for the molecular system investigated exceeded the rate of intermolecular vibrational relaxation k_V in the triplet state T₁ of the donor. The effectiveness of the T-T transfer of energy by vibrationally excited molecules turned out to be higher than the effectiveness of transfer by thermalized ones, but even the highest of them was much less than unity. An increase in the equilibrium temperature of vapors led to a decrease in the effectiveness of transfer for both vibrationally excited and thermalized triplet molecules, thus indicating the importance of the collisional complex in the intermolecular process studied. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 474–479, July–August, 2000.     

Dielectronic recombination and resonant transfer excitation processes for helium-like krypton

The relativistic configuration interaction method is employed to calculate the dielectronic recombination(DR) cross sections of helium-like krypton via the 1s2lnl ’(n = 2,3,...,15) resonances.Then,the resonant transfer excitation(RTE) processes of Kr 34+ colliding with H,He,H 2,and CH x(x = 0-4) targets are investigated under the impulse approximation.The needed Compton profiles of targets are obtained from the Hartree-Fock wave functions.The RTE cross sections are strongly dependent on DR resonant energies and strengths,and the electron momentum distributions of the target.For H 2 and H targets,the ratio of their RTE cross sections changes from 1.85 for the 1s2l2l ’ to 1.88 for other resonances,which demonstrates the weak molecular effects on the Compton profiles of H 2.For CH x(x = 0-4) targets,the main contribution to the RTE cross section comes from the carbon atom since carbon carries 6 electrons;as the number of hydrogen increases in CH x,the RTE cross section almost increases by the same value,displaying the strong separate atom character for the hydrogen.However,further comparison of the individual orbital contributions of C(2p,2s,1s) and CH 4(1t 2,2a 1,1a 1) to the RTE cross sections shows that the molecular effects induce differences of about 25.1%,19.9%,and 0.2% between 2p-1t 2,2s-2a 1,and 1s-1a 1 orbitals,respectively.     

高离化态Cu18+离子的双电子复合及共振转移激发过程的理论研究

在准相对论理论框架下计算了Cu¹⁸⁺离子的双电子复合截面，分析了组态相互作用对截面的影响.基于这些数据，在冲量近似下，通过对靶原子中电子动量分布的卷积，进一步得到了Cu¹⁸⁺与H₂碰撞过程中的共振转移激发截面，并与已有的实验结果作了比较，符合得很好.A 关键词： 双电子复合 共振转移激发     

锁模激光相干激发原子的超窄共振效应

本文提出一种相干激发理论模型,解释了文献[1～3]用锁模激光脉冲序列激发原子产生超窄共振效应的实质.推导了原子密度算符ρA(t)的表示式和光谱信号表示式,给出了有关曲线.而且预言了越窄共振效应的新结果.这一理论模型可推广应用于多光子过程.     

Influence of donor-donor transport on excitation energy transfer

Energy migration and transfer from acriflavine to rhodamine B and malachite green in poly (methylmethacrylate) have been investigated using the decay function analysis. It is found that the influence of energy migration in energy transfer can be described quite convincingly by making use of the theories of Loring, Andersen and Fayer (LAF) and Huber. At high acceptor concentration direct donor-acceptor transfer occurs through Förster mechanism.     

近共振电子态和转动能量传递

为了进一步研究在近共振电子态和非共振电子态转动能量传递的跃迁几率,以一阶含时波恩近似、各向异性Lennard-Jones相互作用势和直线轨迹近似为基础,我们建立了 的碰撞诱导的电子态和转动态的能量传递模型,通过此模型我们得到了实验温度、转动量子数和折合质量对能量传递的影响。     

High order Correlation polarization potential for vibrational excitation scattering of diatomic molecules by low-energy electrons

This paper introduces a correlation--polarization potential with high order terms for vibrational excitation in electron--molecule scattering. The new polarization potential generalizes the two-term approximation so that it can better reflect the dependence of correlation and polarization effects on the position coordinate of the scattering electron. It applies the new potential on the vibrational excitation scattering from N₂ in an energy range which includes the ²П_g shape resonance. The good agreement of theoretical resonant peaks with experiments shows that polarization potentials with high order terms are important and should be included in vibrational excitation scattering.     

含振动能激发Boltzmann模型方程气体动理论统一算法验证与分析

为模拟研究高温高马赫数下多原子气体内能激发对跨流域非平衡流动的影响,将转动能、振动能分别作为气体分子速度分布函数的自变量,把转动能和振动能处理为连续分布的能量模式,将Boltzmann方程的碰撞项分解成弹性碰撞项和非弹性碰撞项,同时将非弹性碰撞按一定松弛速率分解为平动-转动能松弛过程和平动-转动-振动能松弛过程,构造了一类考虑振动能激发的Boltzmann模型方程,并证明了其守恒性和H定理.基于内部能量变量对分布函数无穷积分,引入三个约化速度分布函数,得到一组考虑振动能激发的约化速度分布函数控制方程组,使用离散速度坐标法,基于LU-SGS隐式格式和有限体积法求解离散速度分布函数,建立含振动能激发的气体动理论统一算法.通过开展高稀薄流到连续流圆柱绕流问题统一算法与直接模拟蒙特卡罗法模拟结果对比分析,特别是过渡流区平动、转动、振动非平衡效应对绕流流场与物面力热特性的影响机制,证实了所建立的含振动能激发的Boltzmann模型方程及气体动理论统一算法的准确可靠性.     

Collision-induced rovibrational energy transfer in small polyatomic molecules: the role of intramolecular perturbations

ABSTRACT

Various forms of time-resolved optical double-resonance spectroscopy facilitate rotationally resolved measurements of collision-induced intramolecular vibration-to-vibration (V–V) energy-transfer processes, which take a gas-phase polyatomic molecule from one distinct rovibrational energy level to another. Of longstanding mechanistic interest are questions concerning the extent to which such V–V energy transfer (ET) may be influenced by intramolecular perturbations – notably Fermi resonance (and other anharmonic mixing effects) and Coriolis coupling – within polyatomic molecular rovibrational manifolds of interest. It is evident that quantum-mechanical interference effects can arise, either inhibiting or enhancing the probability of collision-induced ET in perturbed rovibrational manifolds of certain small gas-phase polyatomic molecules, notably CO₂, D₂CO and C₂H₂. This article focuses on a blend of high-resolution rovibrational spectroscopy (characterising initial and final molecular levels and their intramolecular perturbations) and collision dynamics (with colliding molecules defined in terms of isolated-molecule spectroscopic basis states). It aims to offer fresh insights and to consider some apparent mechanistic anomalies (e.g. collision-induced quasi-continuous background effects in the 4ν_CH rovibrational manifold of C₂H₂). Various reported experiments and related theoretical treatments are critically re-examined, in order to pose and address mechanistic questions some of which still challenge detailed understanding.     

近共振电子态和转动能量传递AB(~1∑,J) +C(~sl_j)→AB(~1∑,J′) +C(~sl_(j′))(英文)

1995年沙等在静态池实验中观测到了碰撞诱导转动传能中的量子干涉效应,并且测量到了决定跃迁截面幅值的积分干涉角(J .Chem.Phys.,1995,102 ,2772).同时,孙等在理论上计算了CO A1Π(v=0)~e3∑-(v=1)与He,Ne以及其它碰撞伴的碰撞体系的积分干涉角,建立了相应的理论模型.然而,以前的研究都局限在碰撞伴通常被认为是没有结构的粒子,但是在碰撞过程中相互碰撞的两个粒子都有内部角动量,自旋-轨道相互作用又对反应速率起着非常重要的影响,同时也能够影响反应势垒的高度,因此这种近似忽略了碰撞伴原子对整个碰撞体系得影响.基于这种考虑,在这篇文章中我们从理论上研究AB(~1∑,J) C(~sl_j)→AB(~1∑,J′) C(~sl_(j′))的碰撞诱导的电子态和转动态的能量传递,应用一级含时波恩近似、各向异性L-J相互作用势和直线轨迹近似,建立了理论模型.并讨论和比较了在近共振电子态和非共振电子态两种情况下的振动传能的跃迁几率.     

Measurement of cross-section of excitation transfer from 3s2 to 4s1 and 5s1 energy levels of neon

Collision induced non-radiative transitions in neon plasma have been studied using high intra-cavity radiation field of a 633 nm He-Ne laser. The transitions, induced from 3s ₂ energy level to 4s₁ and 5s₁ groups of energy levels, have been detected as changes in intensities of the spectral lines originating from these energy levels. From these intensity measurements, the quantities governing the transitions i.e. (i)S ₃ ^e /S _3RT , the ratio of the probabilities of electronic deexcitation to the total radiative deexcitation of energy level 3 (ii) 〈r ₂₃ ^e v _e〉, rate of excitation transfer per particle and (iii)S ₂₃ ^e , the total probability for excitation transfer from level 2 to level 3 at a certain value of electron density have been calculated.     

Photo-induced intramolecular electron transfer and intramolecular vibrational relaxation of rhodamine 6G in DMSO revealed by multiplex transient grating spectroscopy

Photo-induced intramolecular electron transfer （PIET） and intramolecular vibrational relaxation （IVR） dynamics of the excited state of rhodamine 6G （Rh6G＋） in DMSO are investigated by multiplex transient grating. Two major compo- nents are resolved in the dynamics of Rh6G＋. The first component, with a lifetime τTPIET = 140 fs-260 fs, is attributed to PIET from the phenyl ring to the xanthene plane. The IVR process occurring in the range ZIVR = 3.3 ps-5.2 ps is much slower than the first component. The PIET and IVR processes occurring in the excited state of Rh6G＋ are quantitatively determined, and a better understanding of the relationship between these processes is obtained.     

相干喇曼诱导甲烷V-T弛豫过程

本文首次报道了用相干喇曼激光诱导红外荧光的方法,研究多原子分于-OH_4的振动能转移过程,并测出v_4振动能级到平动能转移速率常数为:K_(VL)=(8±)×10_(-5).     

Numerical exploration of coherent excitation in three-level ladder systems

The technique of stimulated Raman adiabatic passage (STIRAP) is used to transfer potassium atoms from the 22p state to the 21p Rydberg state through the intermediate state 22s. The results show that complete population transfer is related to pulse duration and overlap, and occurs when the pulse duration and overlap have adequate values. At the same time, population trapping is also formed. Complete population transfer can also occurs when the two-photon resonance condition ({\it\Delta}_s= {\it\Delta}_p) is met.     

Simulation of ball motion and energy transfer in a planetary ball mill

A kinetic model is proposed for simulating the trajectory of a single milling ball in a planetary ball mill, and a model is also proposed for simulating the local energy transfer during the ball milling process under no-slip conditions. Based on the kinematics of ball motion, the collision frequency and power are described, and the normal impact forces and effective power are derived from analyses of collision geometry. The Hertzian impact theory is applied to formulate these models after having established some relationships among the geometric, dynamic, and thermophysical parameters. Simulation is carried out based on two models, and the effects of the rotation velocity of the planetary disk and the vial-to-disk speed ratio ω/Ω on other kinetic parameters is investigated. As a result, the optimal ratio ω/Ω to obtain high impact energy in the standard operating condition at = 800 rpm is estimated, and is equal to 1.15.     

Förster resonant energy transfer in quantum dot layers

Förster resonant energy transfer (FRET) in quantum dot (QD) layer structures has been analyzed. Small and large colloidal CdTe QDs were used as donors and acceptors, respectively. A FRET theory for random donor/acceptor distributions in two dimensions, taking into account exclusion zones around the donors, was applied to characterize FRET in a mixed monolayer. The exclusion zones provide a possibility to include the QD size in the FRET analysis and to determine its impact on the FRET efficiency. The acceptor concentration dependence of the FRET efficiency can also be described within this theory. In a separate donor/acceptor layer structure the distance dependence of the FRET efficiency as well as the acceptor enhancement was investigated. Both were found to agree well with the model of FRET between donor and acceptor layers.     

Sequential excitation energy transfer from naphthalene cascading through titan yellow to fluorescein sodium mediated by (C16Naph(2,6)C4N) vesicles

The sequential excitation energy transfer has been studied in a C₁₆Naph(2,6)C₄N⁺, titan yellow (TY) and fluorescein sodium (FS) ternary aqueous covesicle system. The sequential arrays of chromophores with regulated distance, orders, and orientations were constructed on a non-covalent self-organization system through amphiphilic and electrostatic interaction in aqueous media. The naphthalene group, embedded in the interior of the vesicles, TY and FS anchored on surface of the covesicles through electrostatic interaction, which were employed as donor, mediator and acceptor, respectively, based on overlapping absorption and emission spectra. The sequential energy transfer from naphthalene cascading through TY mediator to FS has been studied in the C₁₆Naph(2,6)C₄N⁺, TY and FS ternary aqueous covesicle system. This sequential excitation energy transfer offers a good model for photoenergy transmission system mimicking photosynthetic systems.