Femtosecond Dynamics of Energy Transfer in Native B800-B850 and B800-Released LH2 Complexes of Rhodobacter Sphaeroides

Two kinds of antenna complexes LH2 of Rhodobacter sphaeroides, wild type RS601 and the removal of B800pigments (B800-released), were used in our experiment. These two LH2 complexes show quite different behaviour in absorption and femtosecond dynamics. By using the femtosecond pump-probe technique, the energy transfer processes occurring in two complexes were studied. Because of removing the B800 pigment from the LH2 in B800-released LH2 complex, the energy transfer between the B800 to B850 pigment was completely eliminated, while the pure internal energy transfer within the exciton states of B850 pigment could be carefully investigated. The results show that, at B800 absorption band, B800-released LH2 obviously shows a dominated transient absorption different from the photobleaching observed in RS601; while at the B850 band, these two complexes show similar photobleaching behaviour.     

Effect of the mutation of carotenoids on the dynamics of energy transfer in light-harvesting complexes （LH2） from Rhodobacter sphaeroides 601 at room temperature

Energy transfers in two kinds of peripheral light-harvesting complexes (LH2) of {Rhodobacter sphaeroides} (RS) 601 are studied by using femtosecond pump--probe spectroscopy with tunable laser wavelength at room temperature. These two complexes are native LH2 (RS601) and green carotenoid mutated LH2 (GM309). The obtained results demonstrate that, compared with spheroidenes with ten conjugated double bonds in native RS601, carotenoid in GM309 containing neurosporenes with nine conjugated double bonds can lead to a reduction in energy transfer rate in the B800-to-B850 band and the disturbance in the energy relaxation processes within the excitonic B850 band.     

Process e^-у→ e^-H in Littlest Higgs Model

In the context of the littlest Higgs （LH） model, we estimate the production cross section of the process e^-у→ e^-H in the future high-energy linear e^＋e^- collider （ILC） with the center-of-mass （CM） energy √S = 500 GeV. Our numerical results show that the contributions of the LH model Co this process are very small in most of the parameter space allowed by the electroweak precision measurement data, and are very diffcult to be detected in the future ILC experiments.     

Correction of the Littlest Higgs Model to Higgs Production Process e-γ→veW-H in e-γ Collisions

The littlest Higgs model is the most economical one among various little Higgs models. In the context of the littlest Higgs （LH） model, we study the process e-γ → veW^-H and calculate the contributions of the LH model to the cross section of this process. The results show that in most of the parameter spaces preferred by the electroweak precision data, the value of the relative correction is larger than 10%. Such correction to the process e-γ →veW^-H is large enough to be detected via e-γ collisions in the future high energy linear e^＋ e^- collider （ILC） experiment with the c.m. energy √s = 500 GeV and a yearly integrated luminosity ￡ = 100fb^-1, which will give an idea/way to test the model.     

Intermediate Energy Coulomb Excitation of Neutron-Rich Nuclei

We reinvestigate the collective effects of the retardation as well as the bending on the Coulomb excitation cross sections and also on the B（E2） strengths of some neutron-rich isotopes using the intermediate energy Coulomb excitation theory. It is found that the B（E2） strengths extracted from the experimental Coulomb excitation cross section data get suppressed approximately by 6%. Furthermore, the obtained B（E2） strengths in the energy range 30-100 MeV/A are found to be in better agreement with the corresponding values known from other sources, than those obtained by using the recoil-corrected relativistic Coulomb excitation theory.     

Statefinder Diagnostic for Born--Infeld Type Dark Energy Model

Using a new method cafled the statefinder diagnostics which can make one dark energy model differ from the others, we investigate the dynamics of Born-Infeld （B-I） type dark energy model. The evolution trajectory of B-I type dark energy with Mexican hat potential model with respect to e-folding time N is shown in the r（s） diagram. When the parameter of noncanonical kinetic energy term η→0 or kinetic energy φ^2 →0, the B-I type dark energy （K-essence） model reduces to the quintessence model or the ACDM model corresponding to the statefinder pair （r, s） = {1, 0} respectively. As a result, the evolution trajectory of our model in the r（s） diagram in Mexican hat potential is quite different from those of other dark energy models. The current values of parameters Ωφ and wφ in this model meet the latest observations WMAP5 well.     

$\phi$-Meson Photoproduction off the protons by using linearly polarized photons in the mid- to higher-$t$ regimes at threshold energies

Observables from vector meson photoproduction by linearly-polarized photons can be expressed in term of bilinear combinations of helicity amplitudes parameterized by the Spin Density Matrix Elements （SDMEs）. These SDMEs give straightforward relations for understanding the nature of the parity exchange at threshold energies, as well as for extracting signatures of the Okubo-Zweig-Iizuka violation. This paper will show preliminary measurements of SDMEs for γp →φp in the photon energy range of 1.7 to 1.9 GeV （momentum transfer squared t range of -1.2 to -0.25 GeV2） and 1.9 to 2.1 CeV （t range of -1.4 to -0.25 GeV2） from the g8b experimental data collected in the summer of 2005 in the Hall B of Jefferson Lab.     

Electromagnetic Transition Strengths and New Insight into the Chirality in ^106Ag

Excited states in ^106Ag are populated through the heavy-ion fusion evaporation reaction ^100Mo（ll B,5n）^106Ag at a beam energy of 60MeV. Lifetimes are measured for transitions of the two negative-parity rotational bands in the nucleus ^106Ag. The reduced transition probabilities show a great difference between the two bands. The staggering of the B（M1） and B（M1）/B（E2） values with spin are not observed. The bands are identified to be built on two distinct quasiparticle configurations. These results are contrary to an earlier suggestion that the pair of bands in ^106Ag are chiral doublet bands.     

Mechanism of Pseudogap Detected by Electronic Raman Scattering： Phase Fluctuation or Hidden Order？

We study the electronic Raman scattering in the cuprates to distinguish the two possible scenarios of the pseudogap normal state. In one scenario, the pseudogap is assumed to be caused by phase fluctuations of the preformed Cooper pairs. We find that pair-breaking peaks appear in both the B1g and B2g Raman channels, and they axe smeared and tend to shift to the same energy with the increasing strength of phase fluctuations. Thus both channels reflect the same pairing energy scale, irrespectively of the doping level. In another scenario, the pseudogap is assumed to be caused by a hidden order that competes with the superconducting order. As an example, we assume that the hidden order is the d-density-wave （DDW） order. We find analytically and numerically that in the DDW normal state there is no Raman peak in the B2g channel in a tight-binding model up to the second nearest-neighbor hopping, while the Raman peak in the Big channel reflects the energy gap caused by the DDW order. This behavior is in agreement with experiments in the pseudogap normal state. To gain further insights, we also calculate the Raman spectra in the DDW＋SC state. We study the doping and temperature dependence of the peak energy in both channels and find a two-gap behavior, which is in agreement with recent Raman experiments. Therefore, our results shed light on the hidden order scenario for the pseudogap.     

Excitonic level structures of LH1 and LH2 of purple photosynthetic bacteria using an analytical approach

The excitonic level structure of a ring-like chain of dimers is discussed analytically in order to aid the understanding of the possible spectral properties of LH1 and LH2 of purple photosynthetic bacteria. Under the approximation of dipole－dipole interaction between Bchls, the excitonic levels, bandwidths and energy gap between two Davydov subbands are expressed analytically in terms of interaction energies and configurational parameters of dipoles. Our model includes all the interactions between pigment molecules in the system. The oscillator strengths and circular dichroism (CD) for the excitonic states are also presented analytically. The simulated absorption and CD spectra of LH1 and LH2 complexes reproduce the main features of the measured results.     

Photoluminescence of Mg—doped GaN with Different Mg Concentrations after Annealing at Different Temperatures

The blue band (BB) in low temperature photoluminescence of Mg-doped GaN films with different Mg concentrations is investigated.The BB peak of as-grown samples with higher Mg concentration centres at lower energy.A shift of the BB peak energy is observed after annealing in N2 at different temperatures,meanwhile,the difference between the BB peak energy is observed after annealing in N2 at different temperatures.Meanwhile,the difference between the BB peak energies diminishes for raised annealing temperature,and the BB peaks for different samples converge to 2.92eV after annealing at 850℃.These experimental results can be accounted for by a model based on compensation effect.The shift of BB lines provides a useful criterion for the optimum annealing temperature of the Mg-doped GaN material,and the value is taken to be 850℃ in our case.     

Influence of Rashba SOI and Polaronic Effects on the Ground-State Energy of Electrons in Semiconductor Quantum Rings

The influence of Rashba spin-orbit interaction （SOI） and polaronic effect on the ground-state energy of electrons in semiconductor quantum rings （QRs） are studied by means of the Lee-Low-Pines variational method. Numerical calculations for GaAs QRs are performed and the results show that the ground-state energy of electrons splits into two branches as E（↑） and E（↓） under the Rashba SOI, which correspond to the spin-up state and spin-down state, respectively. The contribution of the Rashba SOI effect to the ground-state energy of electrons is related to the spin state of electrons and is closely linked to the inner and outer radii of a QR. However, it is independent of the height of the QR. The ground-state energy of electrons decreases due to the polaronic effect in QRs. The energy shift ＆#8710;Ee-LO of the ground-state of the electron induced by the polaronic effect decreases monotonically with increase of the height of a QR and fluctuates with the changes of the radii of QRs. The amplitude of the fluctuation is very sensitive and remarkable to the changes of the inner radius R1 and the outer radius R2.     

Top Quark Flavor Changing Decay t→ cH^0 in Little Higgs Model

We study theoretically the quantum effects of the littlest Higgs model （LH） mediated by flavor changing one-loop Feynman diagrams on the rare decay process t→ cH^0. The comparison of the decay width in the LH model with that in the standard model （SM） is made. We find that the decay branch ratio of t→ cH^0 in the LH model is at most of the order-10^-12, which is two order larger than in the SM. The numerical results show that the difference between the branch ratios in the LH model and the SM is generally sensitive to the LH model parameters, such as symmetry breaking scale f, Higgs boson mass mH0, and x=v＇4f/v^2 in our chosen parameter space, but relatively insensitive to the value choice of the cosine of the mixing angle c and the ratio λ1/λ2.     

Ohmic Radio-Frequency Synergy Current Drive and Transformer Recharging Experiments in the HT-7 Tokamak

Lower hybrid current drive (LHCD) experiments for investigating the interaction between lower hybrid (LH) wave and residual dc electric field were performed in extensive plasma parameter ranges in the HT-7 superconducting tokamak. The experimental results are well fitted to the Karney-Fisch theory on the efficiency of LH waves energy converted to poloidal magnetic field energy. The fraction of absorbed LH power is about 0.75 for the HT-7 machine, and the upshift of the LH-wave parallel refraction index during LHCD experiments have been derived by the optimizing fitting parameters. The LH wave is also used for the transformer recharging when the plasma current is maintained unchanged. The highest efficiency about 7% has been achieved in HT-7 machine.     

Observation of Nano-Dots on HOPG Surface Induced by Highly Charged Arq+ Impact

Highly charged ions （HCIs） have huge potential energy due to their high charge state. When a HCI reaches a solid surface, its potential energy is released immediately on the surface to cause a nano-scale defect. Thus, HCIs are expected to be useful for solid-surface modifications on the nano-scale. We investigate the defects on a highly oriented pyrolytic graphite （HOPG） surface induced by slow highly charged Ar^q＋ ions with impact energy of 20-2000qeV with scanning probe microscopy （SPM）. In order to clarify the role of kinetic and potential energies in surface modification, the nano-defects are characterized in lateral size and height corresponding to the kinetic energy and charge state of the HCIs. Both the potential energy and kinetic energy of the ions may influence the size of nano-defect. Since potential energy increases dramatically with increasing charge state, the potential energy effect is expected to be much larger than the kinetic energy effect in the case of extremely high charge states. This implies that pure surface modification on the nano-scale could be carried out by slow highly charged ions. The mean size of nano-defect region could also be controlled by selecting the charge state and kinetic energy of HCI.     

Theoretical analysis of ion kinetic energies and DLC film deposition by CH4＋ Ar （He） dielectric barrier discharge plasmas

The kinetic energy of ions in dielectric barrier discharge plasmas are analysed theoretically using the model of binary collisions between ions and gas molecules. Langevin equation for ions in other gases, Blanc law for ions in mixed gases, and the two-temperature model for ions at higher reduced field are used to determine the ion mobility. The kinetic energies of ions in CH4 ＋ Ar（He） dielectric barrier discharge plasma at a fixed total gas pressure and various Ar （He） concentrations are calculated. It is found that with increasing Ar （He） concentration in CH4 ＋ Ar （He） from 20% to 83%, the CH4＋ kinetic energy increases from 69.6 （43.9） to 92.1 （128.5）eV, while the Ar＋ （He＋） kinetic energy decreases from 97 （145.2） to 78.8 （75.5）eV. The increase of CH4＋ kinetic energy is responsible for the increase of hardness of diamond-like carbon films deposited by CH4 ＋ Ar （He） dielectric barrier discharge without bias voltage over substrates.     

Simulation of a modified neutron detector applied in CSNS

We simulate the response of a modified Anderson-Braun rem counter in the energy range from thermal energy to about 10 GeV using the FLUKA code. Also, we simulate the lethargy spectrum of CSNS outside the beam dump. Traditional BF3 tube is replaced by the 3He tube, a layer of 0.6 cm lead is added outside the boron doped plastic attenuator and a sphere configuration is adopted. The simulation result shows that its response is exactly fit to H＊（10） in the neutron energies between 10 keV and approximately 1 GeV, although the monitor slightly underestimates H＊（10） in the energy range from thermal energy to about 10 keV. According to the characteristics of the CSNS, this modified counter increases the neutron energy response by 30% compared with the traditional monitors, and it can be applied in other kinds of stray field rich of high eeergy neutrons.