Ultrafast multiplex CARS investigation of vibrational characteristics in chloroform and PMMA

This paper demonstrates the femtosecond time-resolved coherent anti-Stokes Raman scattering by using folded BOXCARS geometry where an ultrashort broadband coherent white light continuum was used as Stokes pulse, and carries out the non-contact detection at long distance, The CARS signal is so easy to be detected that it can be seen even by nude eye. The C-H bonds of chloroform or PMMA were detected and the vibration modes belonging to the side chain and the main chain in PMMA were also compared. Their vibrational characteristics involved decay process and quantum beating were discussed. This modified CARS experimental technique could make up the deficiency of traditional CARS technique.

Theoretical investigation on near-infrared and visible absorption spectra of nanometallic aluminium with oxide coating in nanoenergetic materials:size and shape effects

The effects of metal core dimension, oxide shell thickness and ellipsoid aspect ratio of Al-Al2O3 core-shell nanoparticles on the near-infrared and visible absorption spectra of nanocomposite Al-Al2O3/nitrocellulose（NC） film are investigated by numerical calculations. Both the size-dependent interband transitions and frequency-dependent free electron damping of the nanometallic aluminium are taken into account in the calculations. Oxidation effect of nanoaluminium is also analysed. It is shown that oxidation may enhance but may also reduce the optical absorption, depending on the excited light energy and initial dimension of nanoparticle. Metal core size and excited light energy dominate the absorption characteristic. The absorption ability of ellipsoidal nanoparticles is larger than that of spheroidal nanoparticles and increases by the square index as the aspect ratio increases. These calculations will provide some significant theoretical guidance for the preparation and laser ignition of nanoenergetic materials.

Effect of Pressure on Absorption Spectra of Lycopene in n-Hexane and CS2 Solvents

在 n 己和 CS2 的 lycopene 的吸收系列在高压力下面被测量，结果与 b 叶红素相比。在更低的压力范围，从为 b 叶红素的 Bayliss 参数(BP ) 上的线性依赖的偏差为 lycopene 是比那更可见的。随溶剂 BP 的另外的增加， lycopene 和 b 叶红素红的 0-0 乐队变在几乎在 n 己的一样的率；然而， lycopene 红的 0-0 乐队在 CS2 比 b 叶红素的慢变。这些差异的起源被讨论考虑分散相互作用和溶质和溶剂分子的结构。[从作者抽象]

Thermospin effects in parallel coupled double quantum dots in the presence of the Rashba spin-orbit interaction and Zeeman splitting

The thermoelectric and the thermospin transport properties, including electrical conductivity, Seebeck coefficient, thermal conductivity, and thermoelectric figure of merit, of a parallel coupled double-quantum-dot Aharonov-Bohm interferometer are investigated by means of the Green function technique. The periodic Anderson model is used to describe the quantum dot system, the Rashba spin-orbit interaction and the Zeeman splitting under a magnetic field are considered. The theoretical results show the constructive contribution of the Rashba effect and the influence of the magnetic field on the thermospin effects. We also show theoretically that material with a high figure of merit can be obtained by tuning the Zeeman splitting energy only.

Spin-polarized electronic properties of NiHe_(0.25) under pressure

This paper studies the effects of He atom on the spin-polarized electronic properties of nickel under pressures using ab initio pseudopotential plan-wave method. Under high pressures, the compound of NiHeo.25 can exist and helium- bubble can not create in Ni. A pressure-induced ferromagnetic to paramagnetic phase transition has been predicted in NiHeo.25 at about 218 GPa. It is found that under pressures, the magnetic property of Ni atoms is more strongly affected by He atom than by H atom and that the behaviour of He atom in Ni are completely different from that of H atom, like the bonding characteristics and the electron transfer.

Coherent coupling between vibrational modes of C-H bonds at different positions studied by femtosecond time-resolved coherent anti-Stokes Raman scattering

We performed femtosecond time-resolved coherent anti-Stokes Raman scattering （fs-CARS） measurements on liquid toluene and PVK film. For both samples, we selectively excited the CH stretching vibrational modes and observed the expected quantum beat signals. The frequency of the well-defined beats is in good agreement with the energy difference between the two simultaneously excited modes, which demonstrates that a coherent coupling between the vibrational modes of the C H chemical bonds exists at the different positions of the molecules. The dephasing times of the excited modes are obtained simultaneously.

Quantum superdense coding based on hyperentanglement

We present a scheme for quantum superdense coding with hyperentanglement, in which the sender can transfer four bits of classical information by sending only one photon. The important device in the scheme is the hyperentangled Bell-state analyzer in both polarization and frequency degrees of freedom, which is also constructed in the paper by using a quantum nondemolition detector assisted by cross-Kerr nonlinearity. Our scheme can transfer more informationwith less resources than the existing schemes and is nearly deterministic and nondestructive.

Thermopower in parallel double quantum dots with Rashba spin-orbit interaction

Based on the Green＇s function technique and the equation of motion approach, this paper theoretically studies the thermoelectric effect in parallel coupled double quantum dots （DQDs）, in which Rashba spin-orbit interaction is taken into account. Rashba spin^rbit interaction contributions, even in a magnetic field, are exhibited obviously in the double quantum dots system for the thermoelectric effect. The periodic oscillation of thermopower can be controlled by tunning the Rashba spin^rbit interaction induced phase. The interesting spin-dependent thermoelectric effects will arise which has important influence on thermoelectric properties of the studied system.

Optical Temperature Sensor Using Infrared-to-Visible-Frequency Upconversion in Er ^(3+)/Yb ^(3+)−Codoped Bi3TiNbO9 Ceramics

An optical temperature sensor based on infrared-to-visible upconversion emission in Er ^(3+)/Yb ^(3+)co−doped Bi3TiNbØ9(BTN)ceramics is reported.The fluorescence intensity ratio of the green upconversion photoluminescence(UC−PL)around 524 nm and 545 nm depends on temperature.The operating temperature range and the maximum sensitivity of Er ^(3+)/Yb ^(3+)co−doped Bi_(3)TiNbO_(9) ceramics are 123–693 K and 0.0032 K^(−1),respectively.BTN:Er3+/Yb3+ceramic has good thermal,physical and chemical stability,great UC−PL intensity and low cost fabrication.The results imply that Er ^(3+)/Yb ^(3+)co−doped Bi3TiNbO9 ceramic is promising for applications in wide-temperature-range sensors.

Vibrational relaxation dynamics in transient grating spectroscopy studied by rate equations based on time-dependent correlation function

A modified model, a set of rate equations based on time-dependent correlation function, is used to study vibrational relaxation dynamics in transient grating spectroscopy. The dephasing, the population dynamics, and the vibrational coherence concerning two vibrational states are observed respectively in organic dye IR780 perchlorate molecules doped polyvinyl alcohol matrix. The result shows that in addition to the information concerning system-environment interaction and vibrational coherence, the vibrational energy transfer can be described by this modified model.

Spin Accumulation in a Double Quantum Dot Aharonov-Bohm Interferometer

We investigate the spin accumulation in a double quantum dot Aharonov-Bohm （AB） interferometer in which both the Rashba spin-orbit （RSO） interaction and intradot Coulomb interaction are taken into account. Due to the existence of the RSO interaction, the electron, flowing through different arms of the AB ring, will acquire a spin-dependent phase factor in the tunnel-coupling strengths. This phase factor will induce various interesting interference phenomena. It is found that the electrons of the different spin directions can accumulate in the two dots by properly adjusting the bias and the intradot level with a fixed RSO interaction strength. Moreover, both the magnitude and direction of the spin accumulation in each dot can be conveniently controlled and tuned by the gate voltage acting on the dot or the bias on the lead.

Mechanism of upconversion emission enhancement in Y_3Al_5O_(12):Er^(3+)/Li^+ powders

Er3＋ and Li＋ codoped Y3Al5O12（YAG） powders were prepared for a systematic investigation of their upconversion emissions.X-ray diffraction（XRD）,upconversion emission spectra,pump power dependence,FT-IR spectra and decay time were studied to characterize the samples.With Li＋ doping,the upconversion emission intensity of Er3＋ doped YAG powders was obviously enhanced,accompanied with an increase in the ratio of green to red intensity.The enhancement of emission intensity could be attributed to two mechanisms：one was the distortion of local crystal field around Er3＋,and the other was the decrease in the amount of CO32-and OH-groups.Our results revealed that the latter was the dominant mechanism of the upconversion intensity enhancement in the YAG：Er3＋/Li＋ powders.