Red Shift and Broadening of Backward Harmonic Radiation from Electron Oscillations Driven by Femtosecond Laser Pulse

The characteristics of backward harmonic radiation due to electron oscillations driven by a linearly polarized fs laser pulse are analysed considering a single electron model. The spectral distributions of the electron＇s backward harmonic radiation are investigated in detail for different parameters of the driver laser pulse. Higher order harmonic radiations are possible for a sufficiently intense driving laser pulse. We have shown that for a realistic pulsed photon beam, the spectrum of the radiation is red shifted as well as broadened because of changes in the longitudinal velocity of the electrons during the laser pulse. These effects are more pronounced at higher laser intensities giving rise to higher order harmonics that eventually leads to a continuous spectrum. Numerical simulations have further shown that by increasing the laser pulse width the broadening of the high harmonic radiations can be controlled.

Red-shift law of intense laser-induced electro-absorption in solids

A theoretical study on the red-shift of laser-induced electro-absorption is presented. It is found that laser-induced red-shift scales with the cube root of the pump laser intensity in the optical tunneling regime and has an obvious deviation from this scale in the multi-photon regime. Our results show that in the optical tunneling regime, the laser-induced red shift has the same law as that in the direct current （DC） approximation. Though the scales are the same in the optical tunneling regime, the physical pictures in the two cases are quite different. The electro-absorption in the DC case is a tunneling-assisted transition process, while the laser-induced electro-absorption is a mixed multi-photon process.

Derivatives of 4-dihydroquinolinone and their fluorescent property

A series of donor-π-acceptor （D-π-A） compounds involving varied donors and acceptors as well as a dihydroquinolinone moiety were synthesized. Tuned fluorescent colors from blue to orange were successfully realized in them. Spectroscopic analysis exhibits that the increased conjugated system, enhanced electrondonating ability of acceptor, and electron-withdrawing ability of donor result in red shift in both absorption and fluorescence for these compounds. Both the absorption and fluorescence show strong bathochromic shift effect with the increase in the polarity of solvents. It indicates that they are intramolecular charge transfer （ICT） fluorescent compounds and may have potential application as novel electroluminescent material.

Synthesis,characterization,and theoretical study of N,S-codoped nano-TiO_2 with photocatalytic activities

Nitrogen and sulfur doped titanium dioxide photocatalysts were prepared by the sol-gel method.The products were characterized by X-ray diffraction （XRD）,transmission electron microscopy （TEM）,and UV-visible diffuse reflectance spectra （DRS）.Photocatalytic activities of the samples were investigated on the degradation of methyl orange （MO）.The effect of the dopants on the electronic structure of TiO2 was studied by the first-principles calculations based on the density functional theory （DFT）.The orbital hybridization resulted in energy gap narrowing and electronic delocalization in the crystal of doped TiO2.Mobile electrons of varied energetic states could offer enhanced electron transfer,together with optical absorption improvement.The results show that the doping elements of N and S play a cooperative role in the modification of electronic structure,which enhances the photocatalytic performance.The experimentally observed absorption edges of N-doped TiO2,S-doped TiO2,and N,S-codoped TiO2 are 420,413,and 429 nm,respectively,which can be explained by the theoretical calculation results.

Effect of Energy Transfer on UV Spectra of “H-shaped” Azobenzene Derivatives

A series of “H-shaped” organic dimers （azobenzene derivatives） exhibit linear absorption red shift compared with their corresponding monomers experimentally. Dipolar interaction model is not appropriate for the azobenzene derivatives due to the small distance between two “D-π-A” chains. Energy transfer model is suggested for explanation of the absorption red shift. Two necessary conditions for energy transfer were verified. In addition, bi-exponential florescence-delay behavior of the dimer as well as Bella＇s quantum chemistry calculation shows evidence of energy transfer.

Synthesis of Two Novel Rhenium(I) Bipyridyl Photosensitive Dyes

Two novel rhenium(I) 2, 2'-bipyridyl complexes, [(4,4'-di-COOEt-bipy) Re(CO)3 (NCCH3)PF6] and [(4,4'-di-COOEt-bipy) Re (CO)3 (NCS)], a model complex [(4,4'-di- COOEt-bipy) Re (CO)3 (pyridine)PF6], were synthesized. Their ground stat?electronic spectra and emission spectra were measured in acetonitrile. The MLCT absorption maximum of the complex exhibited a considerable red shift as the ligand changed from pyridine to CNCH3, or SCN.

Broadband time-resolved elliptical crystal spectrometer for X-ray spectroscopic measurements in laser-produced plasmas

The X-ray spectrometer used in high-energy-density plasma experiments generally requires both broad X-ray energy coverage and high temporal, spatial, and spectral resolutions for overcoming the difficulties imposed by the X-ray back- ground, debris, and mechanical shocks. By using an elliptical crystal together with a streak camera, we resolve this issue at the SG-II laser facility. The carefully designed elliptical crystal has a broad spectral coverage with high resolution, strong rejection of the diffuse and/or fluorescent background radiation, and negligible source broadening for extended sources. The spectra that are Bragg reflected （23° 〈 θ 〈 38°） from the crystal are focused onto a streak camera slit 18 mm long and about 80 μm wide, to obtain a time-resolved spectrum. With experimental measurements, we demonstrate that the quartz（1011） elliptical analyzer at the SG-II laser facility has a single-shot spectral range of （4.64-6.45） keV, a typical spectral resolution of E/△E = 560, and an enhanced focusing power in the spectral dimension. For titanium （Ti） data, the lines of interest show a distribution as a function of time and the temporal variations of the He-α and Li-like Ti satellite lines and their spatial profiles show intensity peak red shifts. The spectrometer sensitivity is illustrated with a temporal resolution of better than 25 ps, which satisfies the near-term requirements of high-energy-density physics experiments.

Homo-and Hetero-epitaxial GaSb Layers by MOCVD

Metalorganic chemical vapor deposition(MOCVD) growth of homo-and hetero-epitaxial GaSb has been investigated,by using trimethylgallium(TMGa)and trimetbylantimony(TMSb)as source materials on n-type GaSb and semi-insulating GaAs substrates.The influence of Ⅲ/Ⅴ ratio on the growth of GaSb was studied in detail and it was found that the Ⅲ/Ⅴ ratio range proper for good quality epi-layers is narrow.The carrier mobility and concentration of undoped GaSb epi-layers are about 600 cm^2/Ⅴ·s and 2～4×10^(16)cm^(-3)at room temperature,respectively.The low temperature(77K)mobility is about 5 times of the room temperature's one.The low temperature(11K)photoluminescence(PL)spectrum and the temperature depen- dence of PL spectrum were investigated.The red shift of bound exciton with temperature was observed.

Luminescence Characteristics of Ce^(3+) Doped Ca-Al-Ba Glass

The Al-Ca-Ba glass system with good chemical durability was firstly investigated as the scintillators host. Luminescence properties of Ce3＋ ions in this glass were studied, and obvious red shift and larger stokes shift with respect to others system were investigared. The excellent physical property such as high density and large refractive index implies this glass as an important material for the high quality scintillating fiber.

Fabrication and Photoluminescence Property of CdS Nanowire Array by Template Eiectrodeposition

CdS nanowire arrays were synthesized by altering current（AC） electrodeposition in the porous anodic alumina film prepared by aluminium anodizing in oxalic acid. These nanowires have a uniform diameter of about 45 nm corresponding to the pore size of the films used and length up to several microns. The X-ray diffraction（XRD） pattern indicates that the CdS nanowires crystallize in an hcp structure. Besides, photoluminescences（PL） of CdS nanowire arrays, characterized by spectrophotometer show that CdS nanowries embedded in porous alumina template increases the light-emitting intensity and induces a red shift of PL band.

Study of Shifted UV Emission Peak of ZnO Nanowire Arrays

We have obtained vertically aligned ZnO nanowire arrays synthesized by microwave-assisted heating method with different growth time.From the room-temperature PL measurement,the strong deep-level emission and weak near band edge(NBE)emission can be seen.The deep-level emissions became weaker and deep-level emissions became stronger when the samples were annealed at 300℃for 30 min,meanwhile,the NBE emission peaks get red-shifted with growth time,and the longer the growth time,the more the peak shifting.This phenomenon can be attributed that the diameter of ZnO nanowires increases with growth time.This PL emission phenomenon is important in research of optoelectronic application.

Static spherically symmetric star in Gauss-Bonnet gravity

We explore static spherically symmetric stars in Gauss-Bonnet gravity without a cosmological constant, and present an exact internal solution which attaches to the exterior vacuum solution outside stars. It turns out that the presence of the Gauss-Bonnet term with a positive coupling constant completely changes thermal and gravitational energies, and the upper bound of the red shift of spectral lines from the surface of stars. Unlike in general relativity, the upper bound of the red shift is dependent on the density of stars in our case. Moreover, we have proven that two theorems for judging the stability of equilibrium of stars in general relativity can hold in Gauss-Bonnet gravity.

Theoretical Study on Dihydrogen Bonds of NH3BH3 with Several Small Molecules

The dihydrogen bonds B-H...H-X （X= the complexes of NH3BH3 with HF, HCl, F, Cl, Br, C, O, N） in the dimer （NH3BH3）2 and HBr, H2CO, H20, and CH3OH were theoretically studied. The results show that formation of the dihydrogen bond leads to elongation and stretch frequency red shift of the BH and XH bonds, except that in the H2CO system, the CH bond blue shifts. For （NH3BH3）2 and the complexes of the halogenides, red shifts of the XH bonds are caused by the intermolecular hyperconjugation σ（BH）→σ^＊ （XH）. For the system of H2CO, a blue shift of the CH bond is caused by a decrease of the intramolecular hyperconjugation n（O→σ^＊ （CH）. In the other two systems, the red shift of OH bond is a secondary effect of the stronger traditional red-shifted H-bonds N-H... O. In all these systems, red shifts of the BH bonds are caused by two factors： negative repolarization and negative rehybridization of the BH bond, and decrease of occupancy on σ（BH） caused by the intermolecular hyperconjugation σ（BH）→σ^＊ （XH）.

The Size of a Photon

This paper begins by exploring a useful and neglected detail of a photon—its physical size perpendicular to the direction of propagation in the same way as an atom or neutron has a physical size. Such a photon size would be quite separate from the cross-section of a photonic interaction, which depends on the material interacting. Such a perpendicular dimension of a photon will be invariant under Lorentz transform parallel to the light propagation direction and will thus be the same for all frequencies of light. This study also leads to new details about how a photon interacts, offering an explanation for the familiar physics where light slightly above and below the mean frequency of an excited state can still excite the same state without violation of conservation of energy—a mystery explored thoroughly in a previous paper without finding the solution offered here. As usual, a better elucidation of the details of light interaction also leads to new insights—especially about the vacuum field. The Appendix summarizes some previous research relevant to this

A Non-Newtonian View of the Universe Derived from Hydrodynamic Gravitation and Expanding Earth

Earth Science observations and the Borexino and KamLAND geoneutrino experiments provide clues on the role of aether in the evolution of the Earth, planets, and all other universal structures. Analysis of the problem of storage of aether entering celestial bodies led to a hydrodynamic explanation of gravitation which in turn was found to be closely related to the expanding Earth and to several other phenomena. Variable radius paleogeography provides an approximate assessment of the quantity of ordinary matter added to the planet per time unit, and some inferences about the Earth’s inner energy balance. The aether density, flow rate, and velocity are computed with the help of astrophysics. The origins of cosmological and gravitational redshift are unified under the single cause of gravitation. This is linked to the similar but not interchangeable concept of tired light, which was considered very plausible by cosmologists like Edwin Hubble and Fritz Zwicky. A superluminal speed was calculated for aether at the Earth’s surface. INFN experiments confirm hydrodynamic gravitation and superluminal velocities, and it is possible to identify interrelations of aether parameters with the currently known cosmological parameters H0, G, and c. Unification of hydrodynamic gravitation and the expansion of the celestial bodies through the existence of a minor dissipative force, a non-Newtonian concept, involves a revision of the theories of physics and cosmology, in which the currently accepted laws of physics will be only considered good approximations of a more complex reality.

Carbon interstitial defects causing emission red shift in YAG:Ce phosphor:First-principles calculation

Y3Al5O12:Ce3+ is the most famous phosphor material due to its excellent photolumincent properties.Here,through first-principles calculation,the effect of carbon interstitial defects on Y3Al5O12:Ce3+phosphor was investigated. It is found that the carbon interstitials tend to occupy the next-nearest sites of Ce3+ion in Y3Al5O12:Ce3+ lattice. Specially,these interstitial defects can shorten the Ce3+-O2-bond length, leading to a larger crystal field splitting of 5 d orbital of the Ce3+atom and bigger 5 d centroid shift.These two factors cause the emission spectrum of Y3Al5O12(C):Ce3+red shift compared with that of Y3Al5O12:Ce3+. Moreover, with our comparison experiment, we find that the Y3Al5O12(C):Ce3+ has an obvious red shift compared with that of Y3Al5O12:Ce3+system,which is in accord with our first principles calculation. Our work systematically investigates the impact of the carbon interstitial defect on Y3Al5O12:Ce3+,and provides a new route to tune the emission spectrum in Y3Al5O12:Ce3+.

Highly selective and turn-on fluorescence probe with red shift emission for naked-eye detecting Al^(3+)and Ga^(3+)based on metal-organic framework

A novel ZnII-based metal-organic framework with the formula of{[Zn_(2)(BBIP)_(2)(NDC)_(2)]·H_(2)O}n(JXUST-5)derived from 3,5-bis(benzimidazol-1-yl)pyridine(BBIP)and 1,4-naphthalenedicarboxylic acid(H_(2)NDC)has been synthesized.The adjacent Zn^(II)ions are linked through two BBIP ligands to form a[Zn_(2)(BBIP)_(2)]secondary building unit(SBU).The neighbouring SBUs are further connected by NDC^(2-)withμ2-η^(1):η^(1)andμ2-η^(1):η^(1):η^(1)bridging modes to form a two-dimensional(2D)framework.Topological analysis shows that JXUST-5 could be simplified as an uninodal fes topology with a point symbol of{4.8^(2)}.Furthermore,the 2D framework net could be extended through C-H···πinteraction to form the three-dimensional supramolecular structure.Luminescent experiments suggest that JXUST-5 could selectively and sensitively recognize Al^(3+)and Ga^(3+)through fluorescence enhancement effect along with a relatively large red shift.The detection limits for Al^(3+)and Ga^(3+)are 0.17 and 0.69 ppm,respectively.Interestingly,the sensing process for both Al^(3+)and Ga^(3+)could be directly observed with naked eyes under 365 nm UV lamp.Notably,JXUST-5 could be recycled at least five times as a fluorescent sensor toward Al^(3+)and Ga^(3+),which is the second example of turn-on MOF based fluorescent sensor toward Ga^(3+).

Near-infrared absorbing(>700 nm)aza-BODIPYs by freezing the rotation of the aryl groups

The typical aza-BODIPYs in the dye family are known for bright fluorescence,excellent stability,and tunable absorption wavelengths.Hence,these dyes are attracting the increasing attention.Aza-BODIPYs having the maxima absorption in the near-infrared(NIR)region(650-900 nm)are very favorable for bioimaging in vivo due to the less photo-damage,deeper tissue penetration,and less interference from background auto-fluorescence by biomolecules in the living systems.Many strategies have been employed to modify the structures of the aza-BODIPY core to provide the NIR absorbing dyes.Among these,the most effective method is the fusion of the aromatic rings in aza-BODIPY system.This review allsidedly summarizes the recent development of ring-fused aza-BODIPY dyes(λ_(abs)>700 nm)focusing on the design,synthesis,and potential applications in the NIR region since 2002.

Structural insights into the unusual core photocomplex from a triply extremophilic purple bacterium,Halorhodospira halochloris

Halorhodospira(Hlr.)halochloris is a triply extremophilic phototrophic purple sulfur bacterium,as it is thermophilic,alkaliphilic,and extremely halophilic.The light-harvesting-reaction center(LH1–RC)core complex of this bacterium displays an LH1-Q_(y)transition at 1,016 nm,which is the lowest-energy wavelength absorption among all known phototrophs.Here we report the cryo-EM structure of the LH1–RC at 2.42?resolution.The LH1 complex forms a tricyclic ring structure composed of 16αβγ-polypeptides and oneαβ-heterodimer around the RC.From the cryo-EM density map,two previously unrecognized integral membrane proteins,referred to as protein G and protein Q,were identified.Both of these proteins are single transmembrane-spanning helices located between the LH1 ring and the RC Lsubunit and are absent from the LH1–RC complexes of all other purple bacteria of which the structures have been determined so far.Besides bacteriochlorophyll b molecules(B1020)located on the periplasmic side of the Hlr.halochloris membrane,there are also two arrays of bacteriochlorophyll b molecules(B800 and B820)located on the cytoplasmic side.Only a single copy of a carotenoid(lycopene)was resolved in the Hlr.halochloris LH1–α3β3 and this was positioned within the complex.The potential quinone channel should be the space between the LH1–α3β3 that accommodates the single lycopene but does not contain aγ-polypeptide,B800 and B820.Our results provide a structural explanation for the unusual Q_(y)red shift and carotenoid absorption in the Hlr.halochloris spectrum and reveal new insights into photosynthetic mechanisms employed by a species that thrives under the harshest conditions of any phototrophic microorganism known.

Incorporation of Si-Ninducing white light of SrAl_2Si_2O_8:Eu^(2+),Mn^(2+) phosphor for white light emitting diodes

Photoluminescence （PL） and colorimetric properties of white-light emission SrAl2Si2O8：Eu2＋,Mn2＋ phosphor were tuned effectively through incorporating Si–N bond to the host in the form of Si3N4. A maximum solubility of Si–N bond in SrAl2–xSi2＋xO8–xNx was estimated theoretically to be in a value of x=1.0. Under 365 nm irradiation, a distinct red-shift of blue band emission from 406 to 473 nm for Eu2＋ and an enhancement of yellow band emission peaked at ~565 nm for Mn2＋ were observed with the increase of Si–N content. These effects resulted from partial substitution of Si–N for Al1–O1 and Al4–O2 sites in SrAl2Si2O8 lattice. Eventually, a white emission with CIE chromaticity coordinates （0.287, 0.337） and color rendering index （CRI） 78.3 for SrAl2Si2O8：Eu2＋,Mn2＋ phosphor were achieved upon optimization to a suitable amount of Si–N.