Pulsed upconversion of Tm3+-doped sol–gel silicate glasses

Upconversion processes allow materials to emit light of shorter wavelength than the light incident upon them. Materials with high upconversion efficiency have numerous potential applications in solid-state physics, such as blue upconversion lasers. We study the time-evolution of upconversion fluorescence of Tm³⁺ in a sol–gel glass host following pulsed, red light excitation. The ¹D₂→³F₄ intensity varies quadratically with the laser intensity, indicating a two-photon upconversion mechanism. Maximum upconversion intensity occurred for 0.5% Tm³⁺ with 1% Al³⁺. We analyzed the main relaxation processes affecting the upconversion emission, namely ion clustering and atmospheric water adsorption.     

Radial splitting and confinement in quarkonium

We study the radial splittings of mesons (from light to heavy) in a non-relativistic potential model. We find that the main features of the splittings can be explained by a linear confining potential and discuss expected deviations, as well as predict the radial excitations of \(Q\bar q\) systems such asD ^*′,F ^*′ andB ^*′.     

Scattering of a Light Particle by a System of Harmonic Oscillators

We discuss the asymptotic wave function of a quantum system in ?³ composed by heavy and light particles, in the case where the light particles are in scattering states and no interaction is assumed among particles of the same kind. We first review a recent result concerning the case of K heavy and N light particles, where the one-particle potential acting on each heavy particle decays at infinity. Then we consider the case of one light particle interacting with a system of harmonic oscillators and prove the same kind of result following, with some modification, the proof of the previous case. A possible application to the analysis of the scattering of a light particle from condensed matter is also outlined.     

Systematic investigation of light heavy-ion reactions

We introduce a novel coupling potential for the scattering of deformed light heavy-ion reactions. This new approach is based on replacing the usual first derivative coupling potential by a new, second derivative coupling potential in the coupled-channels formalism. This new approach has been successfully applied to the study of the ¹²C+¹²C, ¹²C+²⁴Mg, ¹⁶O+²⁸Si, and ¹⁶O+²⁴Mg systems and made major improvements over all the previous coupled-channels calculations for these systems. This paper also shows the limitations of the standard coupled-channels theory and presents a global solution to the problems faced in the previous theoretical accounts of these reactions.     

On the possibility of using dark magneto-optical lattices to achieve Bose condensation of atoms

We show that in dark magneto-optical lattices, effects associated with the Bose statistics of atoms can be observed even at laser cooling temperatures (10⁻⁴–10⁻⁶ K), which exceed evaporative cooling temperatures in magnetic traps by several orders of magnitude. Quasicondensation occurs, i.e., the wave function is formed over the distances on which atoms are localized near the bottom of a separate potential well. In addition, switching off the magnetic field adiabatically reduces the temperature significantly, as a result of which Bose condensation in the entire volume of the gas can be observed. We propose a configuration of the light and magnetic fields in which the shape of the three-dimensional magneto-optical potential is independent of the phases of the emerging light waves. Zh. éksp. Teor. Fiz. 113, 2056–2064 (June 1998)     

Real part of the optical potential for composite particles

The optical potential for a composite particle is most simply approximated by the sum of the optical potentials of the constituent nucleons. Restricting ourselves to the real parts of the potentials we use this model as a first approximation in a calculation of the potentials for d, ³He, α and ¹²C. We add corrections for (i) the energy dependence of the nucleon potentials, (ii) three-body terms, (iii) the Pauli principle. All corrections can be important and that for the Pauli principle can be very large. We obtain a good explanation of the following phenomena: (a) the deuteron potential is nearly the sum of the neutron and proton potentials, (b) the potential for ³He is about 20 % less than the sum of the potentials of the nucleons in the ³He projectile, (c) the volume integral of the potential for ³He falls at both high and low energies in the energy range 20–100 MeV, (d) shallow potentials with large radii are found for low energy (30 MeV) scattering of α-particles, (e) deeper potentials are found for higher energy α-particle scattering. We predict shallow potentials for ¹²C scattering from light targets but deeper potentials for heavier targets.     

Photoluminescence of Cu:ZnS, Ag:ZnS, and Au:ZnS nanoparticles applied in Bio-LED

In this work, transition elements, including Cu²⁺, Ag⁺, and Au³⁺, were used to dope in zinc sulfide (ZnS) by chemical solution synthesis to prepare Cu:ZnS, Ag:ZnS, and Au:ZnS nanoparticles, respectively. Transition elements doping ZnS nanoparticles form the electronic energy level between the conduction band and valance band, which will result in the green light emission. There is a zinc sulfide emission shift from blue (~3.01 eV) to green light (~2.15 eV). We also found that Au:ZnS nanoparticles will emit a green light (~2.3 eV) and a blue light (~2.92 eV) at the same time because the mechanism of blue light emission was not broken after Au element had been doped. Furthermore, we used sodium chlorophyllin copper salt to simulate chlorophyll in biological light emission devices (Bio-LED). We combined copper chlorophyll with Cu:ZnS, Ag:ZnS, and Au:ZnS nanoparticles by a self-assembly method. Then, we measured its photoluminescence spectroscopy and X-ray photoelectron spectroscopy to study its emission spectrum and bonding mode. We found that Au:ZnS nanoparticles are able to emit green and blue light to excite the red light emission of copper chlorophyll, which is a potential application of Bio-LED.     

The decay h0 → A0 → A0A0: a complete one-loop calculation in the MSSM

In the minimal supersymmetric standard model the decay h⁰ → A⁰A⁰ of the light neutral scalar h⁰ is kinematically allowed for low values of tan β when radiative corrections to the neutral Higgs masses are taken into account. The width of this decay mode is revisited on the basis of a complete one-loop diagrammatic calculation. We give the analytical expressions and numerical results and compare them with the corresponding ones from the simpler and compact approximations of the effective potential method and the renormalization group approach.     

Absence of Charge-Resonance-Enhanced Ionization in Attosecond Pulse Photoionization： Numerical Result on One-Dimensional H2^＋

We present a numerical result of photoionization rate for the one-dimensional molecular hydrogen ion model exposed to intense light of 1 × 10^16-2×10^16 W/cm^2, 55-as pulse duration, and 800nm wavelength. In contrast to the previous calculation result of charge-resonance-enhanced ionization for lower intensity and much longer pulse, our result exhibits an ionization saturation. The numerical results are interpreted in the field-dressed potential picture as over-the-barrier liberation of electrons. This extremely short pulsewidth and relatively high field phenomenon requests experimental demonstration.     

Alpha-particle and triton cluster states in 19F

We calculate the energies and other properties of three- and four-particle cluster states in the nuclei ¹⁹F and ¹⁹Ne, treated as eigenstat es of a local cluster-core potential. The potential we consider is a symmetrized Saxon-Woods well which has the advantage that a single value of the potential depth can generate rotational spectra of levels with different values of orbital angular momentum L; in this respect, it is very similar to the folding potentials which have been used in previous cluster calculations. We discuss the cluster states in the light of recent three- and four-particle heavy ion transfer reactions and studies of the electromagnetic decay properties of bound and continuum states. Most of the states observed to be strongly populated in the transfer experiments can be unambiguously assigned to cluster bands based on ¹⁶O + t and ¹⁵N + α configurations with various angular momenta and node numbers. Some evidence for mixing between triton and alpha configurations exists and is discussed. We also calculate the electromagnetic properties of the cluster states and find that, with few exceptions, they are in good agreement with the experimental data. Some El transitions are predicted to be very large, contrary to existing experiments, and new experiments are proposed to investigate this discrepancy.     

Collective excitations in low-density 2D electron systems

We report the observation of sharp plasmon and magnetoplasmon modes in ultra-low-density 2D electron systems. Well defined dispersions for the modes are observed at densities as low as 1.1×10⁹ cm⁻² and with excitation wave vectors as large as 1.2×10⁵ cm⁻¹. Interestingly, both modes are found to be more easily measured in low-density systems than in high-density systems. The strength of the light scattering cross-sections at low density suggests potential applications to the study of quantum phase transitions at large r_s.     

发光二极管用SrWO4:Eu3+红光荧光粉激发谱强度的调控

采用化学共沉淀法制备了Eu³⁺掺杂摩尔分数不同、煅烧温度不同的SrWO₄:Eu³⁺系列发光粉体, 所制备的粉体均具有Eu³⁺特征的强室温红光荧光发射. 通过调节煅烧温度和掺杂摩尔分数来调控近紫外和蓝光吸收强度, 进而调控用395 nm的近紫外光和465 nm的蓝光激发样品所得红光发光强度. 研究结果表明, 所制备的SrWO₄:Eu³⁺红光荧光粉可以被紫外和蓝光发光二极管有效激 关键词： 稀土掺杂 4:Eu³⁺')" href="#">SrWO₄:Eu³⁺ 光致发光 白光发光二极管     

Mean field and beyond in nuclei far from stability lines

We calculate, for the first time, the state-dependent pairing gap of a finite nucleus (¹²⁰Sn) diagonalizing the bare nucleon-nucleon potential (Argonne v₁₄) in a Hartree-Fock basis. The resulting gap accounts for about half of the experimental gap. Going beyond the mean field in the particle-particle channel, the combined effect of the bare nucleon-nucleon potential and of the induced pairing interaction arising from the exchange of low-lying surface vibrations between nucleons moving in time reversal states close to the Fermi energy accounts for the experimental gap. Examples for light, halo nuclei are also reported. The more studied effects of the particle-vibration coupling in the particle-hole channel are discussed for the low-lying quadrupole vibration in ¹²⁰Sn and the giant dipole resonance in the unstable oxygen isotopes and ¹³²Sn.     

Phase-locked light sources with low-phase noise for manipulating terahertz-separated metastable states in 40Ca+

We report the development of phase-locked light sources for manipulating terahertz-separated metastable states in ⁴⁰Ca⁺. Two Ti:sapphire lasers with frequencies separated by 1.82 THz are phase-locked using an optical comb generator. The obtained phase noise is 49.8 mrad when the phase-locked loop is closed. Using the developed light sources, we excite Rabi oscillations between the terahertz-separated 3²D_3/2 and 3²D_5/2 states in ⁴⁰Ca⁺. We discuss the phase noises of the light sources and their effect on excitation of Rabi oscillations.     

Super broadband reddish emitting glass with Eu2+ doped for warm-white light-emitting diodes

We present our recent achievements of glasses able to produce ultra-broadband visible fluorescence. The luminescence system was Eu²⁺ doped low silica calcium aluminosilica (LSCAS) glass excited by blue light. The LSCAS glass has the superior properties of oxide glasses and the low phonon energy property of non-oxide glasses. The large Stokes-shift (12163 cm^?1) and smoothing broadband emission (from 450 nm to 800 nm) were explained by the strong electron–phonon interaction and a remarkable nephelauxetic effect. Besides, given the broad excitation band in blue range, the commercialized blue LED will be a good excitation source. Therefore, these glasses have large potential to be used as warm-white light phosphor material.     

Electro-photo modulation of the fermi level in WSe2/graphene van der Waals heterojunction

We report an electro-photo double modulation of the fermi level in a WSe₂/graphene heterojunction. The heterojunction exhibits high I_ON/I_OFF ratio (~10³) in transfer characteristic in dark and distinct rectification behavior in output characteristic under light illumination, respectively. Time-dependent photoresponse reveals that the heterojunction has a considerable potential in the application of photodetection. Interestingly, an exotic current peak is observed in transfer characteristic under light illumination. This novel behavior is attributed to the tunable fermi level at the WSe₂/graphene heterojunction by electro-photo double modulation. The results may be helpful to develop tunable photovoltaic optoelectronics based on van der Waals heterojunctions.     

A three-center shell model for ternary fission

We propose a generalization of the phenomenological shell model based on the harmonic oscillator potential with spin-orbit term andl ²-corrections to systems made up of three clusters. The centers of these may be in arbitrary geometrical configurations and the clusters may be of different masses. The method of determining the eigenstates of the single-particle Hamiltonian is sketched and results for the cluster structure of light nuclei and the ternary fission of a superheavy system are presented.     

Upconversion white-light emission in Ho³⁺/Yb³⁺/Tm³⁺ tridoped LiNbO₃ single crystal

Ho³⁺/Yb³⁺/Tm³⁺ tridoped LiNbO₃ single crystal exhibiting intense upconversion white light under 980?nm excitation has been successfully fabricated by the Czochralski method. The tridoped LiNbO₃ single crystal offers power dependent color tuning properties by simply changing excitation power. Efficient three-photon blue upconversion emission and two-photon green and red upconversion emissions have been observed. In addition, the red emission of Ho³⁺ originates dominantly from the nonradiative decay of green emission. The LiNbO₃ with upconversion white light will be a potential laser candidate material.