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.

Phonon-assisted excitation energy transfer in photosynthetic systems

The phonon-assisted process of energy transfer aiming at exploring the newly emerging frontier between biology and physics is an issue of central interest.This article shows the important role of the intramolecular vibrational modes for excitation energy transfer in the photosynthetic systems.Based on a dimer system consisting of a donor and an acceptor modeled by two two-level systems,in which one of them is coupled to a high-energy vibrational mode,we derive an effective Hamiltonian describing the vibration-assisted coherent energy transfer process in the polaron frame.The effective Hamiltonian reveals in the case that the vibrational mode dynamically matches the energy detuning between the donor and the acceptor,the original detuned energy transfer becomes resonant energy transfer.In addition,the population dynamics and coherence dynamics of the dimer system with and without vibration-assistance are investigated numerically.It is found that,the energy transfer efficiency and the transfer time depend heavily on the interaction strength of the donor and the high-energy vibrational mode,as well as the vibrational frequency.The numerical results also indicate that the initial state and dissipation rate of the vibrational mode have little influence on the dynamics of the dimer system.Results obtained in this article are not only helpful to understand the natural photosynthesis,but also offer an optimal design principle for artificial photosynthesis.

Surveying the role of excitation energy in probing nuclear dissipation

A dynamical Langevin model is employed to calculate the excess of the evaporation residue cross sections of the ^194Pb nucleus over that predicted by the standard statistical model as a function of nuclear dissipation strength. It is shown that large excitation energy can increase the effects of nuclear dissipation on the excess of the evaporation residues and the sensitivity of this excess to the dissipation strength,and that more higher excitation energies have little contribution to further raising this sensitivity. These results suggest that on the experimental side,producing those compound systems with moderate excitation energy is sucient for a good determination of the pre-saddle nuclear dissipation strength by measuring the evaporation residue cross section,and that forming an extremely highly excited system does not considerably improve the sensitivity of evaporation residues to the dissipation strength.

STUDIES OF THE ANTENNA EFFECT IN POLYMER MOLECULES ENERGY MIGRATION AND TRAPPING IN NAPHTHALENE-CONTAINING POLYELECTROLYTES

Polymers of 1- and 2-vinylnaphthalene containing more than about 50 mol% sulfonic acid groups dissolve in water to form 'hypercoiled' conformations which have many of the properties of micelles. Hydrophobic molecules such as anthracene and perylene are selectively absorbed in these pseudo micellar structures, and their fluorescence emission is sensitized by energy transfer from the surrounding naphthalene chromophores. When irradiated with UV light in the presence of oxygen, the emission of perylene rapidly decreases. It is proposed that this is due to reaction of singlet oxygen with the perylene trapped in the hypercoiled polymer. (Author abstract) 3 Refs.

Packing Structures of Thiophene Dimers and Their Effects on Excitation Energies of Thiophene Dimers

The packing structures of thiophene dimers and their effects on excitation energies of thiophene dimers were studied by employing MP2/6-31 ＋ G^＊ and TDDFT calculations. Twelve Optimized dimers with different orientations were obtained by means of MP2/6-31 ＋ G ^＊ optimizations. Among them, five T-shaped and three π-stacked thiophene dimers are local minima in energy. The result shows that the preferable conformation of thiophene dimers is the T- shaped packing, which is in agreement with the results in references. All the excitation energies of both T-shaped dimers（5. 34-5. 48 eV） and π-stacked dimers（5. 15-5. 18 eV） are lower than that of the isolated thiophene（5.68 eV）, indicating that inter-ring interactions decrease the excitation energies.

A piezoelectric energy harvester based on internal resonance

A vibration-based energy harvester is essentially a resonator working in a limited frequency range.To increase the working frequency range is a challenging problem.This paper reveals a novel possibility for enhancing energy harvesting via internal resonance.An internal resonance energy harvester is proposed.The excitation is successively assumed as the Gaussian white noise,the colored noise defined by a second-order filter,the narrow-band noise,and exponentially correlated noise.The corresponding averaged root-meansquare output voltages are computed.Numerical results demonstrate that the internal resonance increases the operating bandwidth and the output voltage.

Doped all-inorganic cesium zirconium halide perovskites with high-efficiency and tunable emission

Doping enables manipulation of both the electrical and optical properties of halide perovskites.Herein,we incorporated Te^(4+) into Cs_(2)ZrCl_(6) single crystal,simultaneously preserving the vacancy-ordered structure,to obtain an efficient yellow-emitting perovskite with a near-unity photoluminescence quantum yield(PLQY≈97.6%).Te^(4+) doping modifies the hue and emission color of pristine Cs_(2)ZrCl_(6),generates new absorption channels,and successfully extends the excitation energy from<280 nm to 360-450 nm range.Detailed spectral characterizations,including ultrafast femtosecond transient absorption measurements,reveal that the bright yellow light is derived from triplet self-trapped excitons.Moreover,further tuning doping concentration enables Te-doped Cs_(2)ZrCl_(6) single crystals to exhibit efficient warm white light emission.This work provides a new perspective for the development and design of stable lead-free perovskites with highly efficient luminescence.

Variational Calculation of the Doubly-Excited States Nsnp of He-Like Ions via the Modified Atomic Orbitals Theory

In this paper, we have declined the formalism of the method of the Modified Atomic Orbital Theory (MAOT) applied to the calculations of energies of doubly excited states 2snp, 3snp, and 4snp Helium-like systems. Then we also applied the variational procedure of the Modified Atomic Orbital Theory to the computations of total energies, excitation energies of doubly-excited states 2snp, 3snp, 4snp types of Helium-like systems. The results obtained in this work are in good agreement with the experimental and theoretical values available.

Theoretical Investigation of Nonlinear Optical Properties of Organicand Transition Metal Hybrid Azobenzene Dendrimers

In this work, we report a theoretical exploration of the responses of organic azobenzene dendrimers. The polarizabilities, the first and second hyperpolarizabilities of the azobenzene monomers （GO）, and the first, second and third generation （G1, G2 and G3, respectively） are investigated by semi-empirical methods. The calculated results show that the nonlinear optical （NLO） properties of these organic dendrimers are mainly determined by the azobenzene chromospheres. Additionally, the values oft and y increase almost in proportion to the number of chromophores. On the other hand, two types of transition metal hybrid azobenzene dendrimers （core-hybrid and branch-end hybrid according to the sites combined with transition metals） are simulated and discussed in detail in the framework of time-dependent density functional theory （TDDFT）. The calculated results reveal that the NLO responses of these metal dendrimers distinctly varied as a result of altering the charge transfer transition scale and the excitation energies.

High-k Structures in (124)～Cs

High spin states in the odd-odd nucleus 124Cs have been investigated through the fusion-evaporation reaction 116Sn（11B, 3n）l24 Cs with a beam energy of 45 MeV. A new rotational band is established and assigned as the high-k configuration of πg9/2140419/2＋ ⊙vh 11/2[523]7/2-. Some structures linking to this band have also been observed. According to the results of the excitation energy systematics, the lowest level of this band is assigned as 9-, and the 8- isomer bandhead has not been observed. Another isomer with a half life of 6.3 s has also been observed with its new decay paths established, Its excitation energy is raised by 79 keV, but its Iπ is not changed.

Electron population properties with different energies in a helicon plasma source

The characteristics of electrons play a dominant role in determining the ionization and acceleration processes of plasmas.Compared with electrostatic diagnostics,the optical method is independent of the radio frequency(RF)noise,magnetic field,and electric field.In this paper,an optical emission spectroscope was used to determine the plasma emission spectra,electron excitation energy population distributions(EEEPDs),growth rates of low-energy and highenergy electrons,and their intensity jumps with input powers.The 56 emission lines with the highest signal-to-noise ratio and their corresponding electron excitation energy were used for the translation of the spectrum into EEEPD.One discrete EEEPD has two clear different regions,namely the low-energy electron excitation region(neutral lines with threshold energy of13–15 eV)and the high-energy electron excitation region(ionic lines with threshold energy?19 e V).The EEEPD variations with different diameters of discharge tubes(20 mm,40 mm,and 60 mm)and different input RF powers(200–1800 W)were investigated.By normalized intensity comparison of the ionic and neutral lines,the growth rate of the ionic population was higher than the neutral one,especially when the tube diameter was less than 40 mm and the input power was higher than 1000 W.Moreover,we found that the intensities of low-energy electrons and high-energy electrons jump at different input powers from inductively coupled(H)mode to helicon(W)mode;therefore,the determination of W mode needs to be carefully considered.

Equation-of-motion/Linear-response Coupled Cluster Methods with an Approximate Treatment on Triples for Singly-excited States with Pronounced Double Excitation Character

In this work,we investigate the performance of various equation-of-motion/linear-response coupled cluster(EOM/LR-CC)methods with an approximate treatment for triples on excitation energies(EEs)by comparing with EOM-CCSDT(SDT=single,double,triple excitations)results.The focus of this work is on singly-excited states with percentages of the single excitation part(R_(1),%)from CC3 between 50%and 80%,i.e.,excited states with a pronounced double excitation character.CC3 is shown to provide EEs that agree well with EOM-CCSDT results for such excited states.Moreover,reliable EEs can be obtained with EOM-CCSD(T)(a)^(*) and CCSDR(3)for excited states with R1 from CC3 larger than 80%.As for singly-excited states with R1 from CC3 between 80%and 50%,EEs with EOM-CCSD^(*),CCSDR(T)andδ-CR-EOM-CC(2,3)-D agree reasonably well with those of EOM-CCSDT.However,it is too costly to choose a proper method for singly-excited states based on R_(1) of CC3 since CC3 is a rather expensive method.On the other hand,our results show that difference between EEs with EOM-CCSD and EOM-CCSD(T)(a)*[ΔE_((T)(a)*)]correlates well with R1 from CC3 andΔE_((T)(a)*)is about 0.25 eV when R_(1)(CC3)is 80%.Appropriate methods to obtain reasonable EEs for singly-excited state can be chosen based on whetherΔE_((T)(a)*)is larger than 0.25 eV.

Ion stopping in dense plasmas: A basic physics approach

We survey quite extensively the present research status of ion-stopping in dense plasmas of potential importance for initial confinement fusion(ICF)drivenby intense and heavy ion beams,and alsofor warm dense matter(WDM).First,we putemphasis on every possible mechanism involved in the shaping of the ion projectile effective charge,while losing energy in a target plasma with classical ions and partially degenerate electrons.Then,we switch to ion stopping by target bound electrons,taking detailed account of mean excitation energies.Free electron stopping has already been given a lot of attention in former works[C.Deutsch et al.,Recent Res.Devel.Plasma 1(2000)1-23;Open Plasma Phys.J.3(2010)88-115].Then,we extend the usual standard stopping model(SSM)framework to nonlinear stopping including a treatment of the Z 3 Barkas effect and a confronting comparison of Bloch and Bohr Coulomb logarithms.Finally,we document low velocity ion slowing down(LVISD)in single ion plasmas as well as in binary ionic mixtures(BIM),in connection with specific ICF fuels.

The Parametric Identification of a System with Unclear Input information

This paper develops an average power and energy method for the parametric identification of a system. The new method makes it possible to identify the parameters of a system depending only on its output information, and can be used in both linear and non-linear systems.

Variational Calculations of Energies of the (2<i>snl</i>) ^1,3<i>L^π</i>and (2<i>pnl</i>) ^1,3<i>L^π</i>Doubly Excited States in Two-Electron Systems Applying the Screening Constant per Unit Nuclear Charge

In this paper, resonance energies and excitation energies of doubly 2sns 1,3Se, 2snp 1,3P0, 2pnp 1,3De, 2pnd 1,3F0 and 2pnf 1,3Ge excited states of the helium isoelectronic sequence with Z ≤ 10 are calculated. Calculations are carried out in the framework of the variational procedure of the formalism of the Screening Constant per Unit Nuclear Charge (SCUNC). New correlated wave function of Hylleraas type is used. Precise resonance and excitation energies are tabulated and good agreement is obtained when a comparison is made with available literature values.

Ligand-dependent aggregation-enhanced photoacoustic of atomically precise metal nanocluster

Atomically precise metal nanoclusters(MNCs),as a potential type of photoacoustic(PA)contrast agent,are limited in application due to their low PA conversion efficiency(PACE).Here,with hydrophilic Au25SR18(SR=thiolate)as model NCs,we present a result that weakly polar solvent induces aggregation,which effectively enhances PA intensity and PACE.The PA intensity and PACE are highly dependent on the degree of aggregation,while the aggregation-enhanced PA intensity(AEPA)positively correlates to the protected ligands.Such an AEPA phenomenon indicates that aggregation actually accelerates the intramolecular motion of Au NCs,and enlarges the proportion of excited state energy dissipated through vibrational relaxation.This result conflicts with the restriction of intramolecular motion mechanism of aggregation-induced emission.Further experiments show that the increased energy of AEPA originates from the aggregation inhibiting the intermolecular energy transfer from excited Au NCs to their surrounding medium molecules,including solvent molecule and dissolved oxygen,rather than restricting radiative relaxations.This study develops a new strategy for enhancing the PA intensity of Au NCs,and contributes to a deeper understanding of the origin of the PA signal and the excited state energy dissipation processes for MNCs.

Forced vibration control of an axially moving beam with an attached nonlinear energy sink

This paper investigates a highly efficient and promising control method for forced vibration control of an axially moving beam with an attached nonlinear energy sink（NES）.Because of the axial velocity,external force and external excitation frequency,the beam undergoes a high-amplitude vibration.The Galerkin method is applied to discretize the dynamic equations of the beam–NES system.The steady-state responses of the beams with an attached NES and with nothing attached are acquired by numerical simulation.Furthermore,the fast Fourier transform（FFT）is applied to get the amplitude–frequency responses.From the perspective of frequency domain analysis,it is explained that the NES has little effect on the natural frequency of the beam.Results confirm that NES has a great potential to control the excessive vibration.

Calculation of vibrational energy transition rates in acoustic relaxation processes for excitable gas molecules

To research the correlation between vibrational energy transition rates and acoustic relaxation processes in excitable gases, the vibrational relaxation theory provided by Tanczos [J. Chem. Phy3. 25, 439 （1956）] is applied to calculate the energy transition rates of Vibrational- Vibrational （V-V） and Vibrational-Translational （V-T） energy transfer in gas mixtures. The results of calculation for the multi-relaxation processes in various gas mixtures, consisting of carbon dioxide, methane, chlorine, nitrogen, and oxygen at room temperature, demonstrate that the acoustic energy stagnated in every vibrational mode is coupled with each other through V-V energy exchanges. The vibrational excitation energy will relax through the V-T de-excitation path of the lowest mode because of its fastest V-T transition rate, resulting in that only one absorption peak can be measured for most of excitable gas mixtures. Thus, an effective model is provided to analyze how the vibrational energy transition rates affect the characteristics of acoustic relaxation processes and acoustic propagation in excitable gas mixtures.

The NUBASE2020 evaluation of nuclear physics properties

The NUBASE2020 evaluation contains the recommended values of the main nuclear physics properties for all nuclei in their ground and excited,isomeric(T1/2≥100 ns)states.It encompasses all experimental data published in primary(journal articles)and secondary(mainly laboratory reports and conference proceedings)references,together with the corresponding bibliographical information.In cases where no experimental data were available for a particular nuclide,trends in the behavior of specific properties in neighboring nuclei were examined and estimated values are proposed.Evaluation procedures and policies that were used during the development of this evaluated nuclear data library are presented,together with a detailed table of recommended values and their uncertainties.

Calculation of prompt fission neutron spectrum for ^(233)U(n,f) reaction by the semi-empirical method

The prompt fission neutron spectra for the neutron-induced fission of 233U for low energy neutrons （below 6 MeV） are calculated using nuclear evaporation theory with a semi-empirical method, in which the partition of the total excitation energy between the fission fragments for the nth＋233U fission reactions is determined by the available experimental and evaluation data. The calculated prompt fission neutron spectra agree well with the experimental data. The proportions of high-energy neutrons of prompt fission neutron spectrum versus incident neutron energies are investigated with the theoretical spectra, and the results are consistent with the systematics. The semi-empirical method could be a useful tool for the prompt evaluation of fission neutron spectra.