We demonstrate that broadband impulsive stimulated Raman scattering with transient grating experimental geometry is capable of recording vibrational spectra in time and frequency domains to reveal the dissociation mechanism of liquid CH3I. The repulsive 3Q0 potential energy surface is modified to a quasi-bound surface in the liquid CH3I due to the solvent cage, making the wave packets to get trapped. A small portion of the wave packet passes through the solvent cage, resulting in the CI bond breakage with the product I2. This work provides a first glimpse of immense potential of BB-ISRS in studying photodissociation dynamics in liquids.

The electric discharge spark dissociation of gas CH3I is found to be similar to its femtosecond laser photodissociation. The almost identical spectra of the two processes show that their initial ionization conditions are very similar. The initial ionization followed by molecular fragmentation is proposed as the dissociation mechanism, in which the characteristic emissions of I+, CH3, CH2, CH, H, and I2 are identified as the dissociation products. The emission band of 505nm I2 is clearly observed in the time-resolved laser induced breakdown spectroscopy (LIBS). The dynamic curve indicates that I2∗ molecules are formed after the delay time of ∼4.7ns. The formation of I2∗ molecule results from the bimolecular collision of the highly excited iodine atom I∗(4P) and CH3I molecule. This dynamical information can help understand the process of electric discharge spark dissociation of CH3I.

In order to obtain the thermal physical parameters of nitrocellulose (nitrogen content 11.89%~13.5%) to make the thermal analysis calculations and reveal the reaction dynamics mechanism, laser flash method and differential scanning calorimetric (DSC) method were used to measure the thermal physical parameters of nitrocellulose with nitrogen content 12%(NC(12%N)). The values of thermal diffusivity, specific heat capacity, and thermal conductivity were obtained at temperature ranging from 25℃to 140 ℃.Results show that with the increase of temperature, the specific heat capacity increases, while the thermal conductivity and thermal diffusivity decrease.But the changes are not obvious.So these parameters can be determinatal as:in the calculation of thermal analysis:cp =1.131 J? g-1? K-1 ,D=0.413 mm2? s-1 ,λ=0.142 W? m-1? K-1 .

Solvent polarity effect on the absorption spectra and fluorescence spectra of a series of multibranched structure triphenylamine derivations (Ph-G0, Ph-G1, and Ph-G2) were analyzed to reveal the factors that determine the two-photon absorption (TPA) ability in these molecules. It was found that the dominate factor is the extent of intramolecular charge transfer upon photoexcitation, rather than coherent coupling between branches. This result suggests that it is more effective to change the electron withdrawing ability or electron giving ability of branches and core than simply increase the number of branches for enhancing the TPA ability in multibranched structure molecules.

The change of Q-band fluorescence lifetime of tetraphenyl porphyrins (TPP) adsorbed on the surface of silver nanoparticles is reported. The lifetime is extended when the surface plasmon resonant peak of silver nanoparticles is adjusted to be resonant with the Q-absorption band, which is due to the fact that silver nanoparticles bring a large surface plasmon resonant enhancement effect to the surface light field, and the excited TPP molecules have a higher polarity. The enhanced light field will stabilize the TPP molecules of high polarity, which causes the extended Q-band fluorescence lifetime. It has an important significance in photodynamic therapy using porphyrins as photosensitizer.

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.

The longitudinal ultrasonic wave launched by ns-laser pulse is used to measure the temperature dependence of the elastic modulus C33 of single crystal sapphire. The result shows that in a temperature from room temperature to 1000 ℃ the elastic modulus of sapphire C33 reduces as the temperature increases, following the relationship C33 = - 1.541 10-5T2 - 0.021T + 498.3. In this method, the ablation mechanism is adopted to launch strong longitudinal waves, therefore, the result is accurate that the error of the measurement is estimated to be no more than 0.1%.

The shock wave driven by short laser pulse is used to study the damage of brittle material K9 glass. The damage morphology of K9 glass surface indicates that the material has experienced different loading modes, respectively, at the central area and the surrounding area of the shock wave. At the central area of shock wave, the wavefront is plane and has a uniform pressure distribution, the material mainly suffers a longitudinal shock pressure; but on the edge the shock wave, the wavefront is approximately spherical, besides longitudinal pressure, transverse tensile stress will emerge inside the material. In the latter case, the damage threshold of the material is much smaller than that in the case of compressing by longitudinal pressure only. According to the relationship between damage area and shock pressure, an experimental method is proposed to measure the damage threshold of materials under shock loading. The damage threshold of K9 glass under spherical shock wave is measured to be about 1.12 GPa; and the damage threshold under plane shock wave is estimated to be between 1.82 and 1.98 GPa. They are much bigger than the damage threshold under static pressure. This method could also be used to measure the damage threshold of other materials when loaded by dynamic pressure. (C) 2011 American Institute of Physics. [doi:10.1063/1.3564961]

An accurate and simple method, Raman peak-shift simulation, is proposed to determine the characteristics of a laser-driven shock wave. Using the principle of the Raman peaks shifting at high pressure and the pressure distribution in the gauge layer, the profile of the Raman peak can be numerically simulated. Combined with time-resolved Raman spectroscopy, some main characteristics of the shock wave were determined. In the experiment, polycrystalline anthracene was used as the pressure gauge. The pump-probe technique was used to obtain the time-resolved Raman spectra of anthracene under shock loading. The velocity of the shock wave, the peak pressure and the rise time of the shock front were determined by simulating the experimental spectra numerically. The result shows that the method of Raman peak-shift simulation is effective in obtaining the characteristics of a laser-driven shock wave. Copyright (C) 2010 John Wiley & Sons, Ltd.

A modified photon echo (PE) technique, the supercontinuum probing photon echo (SCPPE), is introduced and performed to investigate the vibrational coherence in organic dye IR780 perchlorate doped polyvinyl alcohol (PVA) film. The coherences of multiple vibrational states which belong to four vibrational modes create complex oscillations in SCPPE signal. The frequencies of vibrational modes are confirmed from the results of Raman calculation which accord fairly well with the results of Raman scattering experiment. Compared with conventional one-color PE, the SCPPE technique can realize broadband detection and make the experiment about vibrational coherence more efficient.

The excited states of a symmetric D-π-D structure two-photon excited fluorescence material 1,4-di (4′-N,N-diphenylaminostyryl) benzene (DPA-DSB) have been investigated by spectroscopic experiments and quantum chemical calculations. The solvent polarity dependent fluorescence properties indicate that upon photoexcitation, a radiative intramolecular charge-transfer (ICT) state is formed resulting from the ICT process. The molecular structure does not have large change during the ICT process, which is confirmed by the quantum chemical calculations performed by Gaussian 03 software. The planar structure of the fluorescent ICT state results in the high fluorescence quantum yield which is important in the two-photon excited fluorescence application.

Single-phase Bi0.85La0.1Ho0.05FeO3 multiferroic ceramics were prepared by a rapid liquid sintering method. The ceramics exhibited an obvious ferroelectric loop with a remnant polarization of 11.2 mu C/cm(2) and also showed weak ferromagnetism with the remnant magnetization of 0.179 emu/g at room temperature. A considerable enhancement of the polarization on magnetic poling and a dielectric anomaly in the vicinity of the antiferromagnetic transition temperature due to the intrinsic magnetoelectric coupling effect were observed in Bi0.85La0.1Ho0.05FeO3 ceramics. The dielectric constant for the Bi0.8La0.1Ho0.05FeO3 samples at room temperature decreases with increasing applied magnetic fields, and the coupling coefficient (epsilon'(H) epsilon'(0))/epsilon'(0) reaches -1.04% at H = 10 kOe. (C) 2011 Elsevier B. V. All rights reserved.

The photoluminescence properties of the blend films consisting of organic small molecules and nanocrystals (NCs)--Alq3 and CdSeS NCs--were studied by steady-state and time-resolved photoluminescence (PL) spectroscopy with different excited wavelengths. Both the fluorescence intensity and lifetime are intensively dependent on the NC concentration. The detailed analysis of experiment data proves that Forster energy transfer from the Alq3 to the NCs exists simultaneously with the charge transfer and both compete with each other in the blend films.

The photoluminescence (PL) properties of the guest–host films, using CdTeS/ZnS core shell quantum dots (QDs) as the guest and organic small-molecule material Alq3 as the host, are studied by steady-state and time-resolved PL spectroscopy. Both the relative intensity and the PL lifetime are intensively dependent on the weight ratio of Alq3 and CdTeS/ZnS QDs. The detailed analysis provides clear evidence for a Förster energy transfer from Alq3 host to QDs guest, based on the nonradiative resonant transfer mechanism. The results are relevant to the application of hybrid organic/inorganic systems to OLEDs.

The impact of noble metal nanostructures on the surface trapping state of semiconductor quantum dots was investigated by taking nanosecond time resolved photoluminescence measurements. It was observed that nonradiative resonant energy transfer from the excitonic state of quantum dots to Au nanofilm reduced the lifetime and intensity of excitonic state emission. No nonradiative resonant energy transfer from surface trapping state to Au nanofilm was observed. It is possibly implied that noble metal nanostructures have no impact on the surface trapping state of semiconductor quantum dots.

Inspired by spiral development method in software engineering, we explore a new top-down design method in Matlab environments. Data acquisition and data-out devices which can work in Matlab environments are designed, including the digital filter and coherent detection procedures for eddy current detection. In this way, rapid eddy current detection prototyping can be designed very soon, and it is useful for system-level devices design in eddy current detection.

In this study, 70wt.% Ni/Al2O3 was prepared via a glycine–nitrate combustion method and applied as the catalyst for decomposing methane into hydrogen and carbon nanotubes that can be applied in polymer-electrolyte-membrane fuel cell (PEMFC). The methane conversion and the hydrogen content in the effluent gas reached 71 and 83%, respectively, at an operating temperature of 700°C under ambient pressure. I–V tests demonstrated that the methane is inert to the electro-catalyst and acts mainly as a diluting gas. A porous Al2O3-supported thin-film Pd membrane was integrated with the catalytic methane decomposition process. Due to the high initial hydrogen content, even an imperfect Pd membrane, effectively increased the hydrogen content to >98%, which resulted in only a slight performance loss of ∼10% compared to the application of pure hydrogen as the fuel. The advantages, such as continuous hydrogen separation, simple process, high reliability and value-added by-product, all make this process highly attractive for future PEMFC application.

Photoinduced damage behavior of mesotetraphenylporphyrin (TPP) under one- and two-photon excitation with femtosecond laser pulses is investigated in the present work. Quenching in the luminescent intensity is observed. Results suggest that laser irradiation on TPP mainly causes two simultaneously occurring photoprocesses: photodamage and formation of a porphine-type photoproduct. The damage rate exhibits a linear dependence on the incident light power in one-photon excitation, whereas in two-photon excitation, the power dependence of the damage rate turns out to be exponential. The photoproduct formed in one- and two-photon excitation is identical. This product, which is observed to possess superior photostability and two-photon absorbing ability compared with the original TPP sensitizer, is likely to be treated as a secondary photosensitizer in the activation process of photodynamic therapy (PDT). This work might be helpful for the drug evaluation in the practical application of PDT.

The temporal evolution of excited states of a symmetric D-π-D structure two-photon absorption material, 1,4-di(4′-N,N-diphenylaminostyryl) benzene (DPA-DSB), was investigated by femtosecond transient absorption spectrum and solvent polarity dependent fluorescence properties. The results suggested that the structure of DPA-DSB did not change much during the intramolecular charge-transfer (ICT) process, which could be the reason for good radiative ability of the ICT state. The major non-radiative deactive channel may be a large structure-changed process, which was formed more slowly than the radiative ICT state. Symmetric charge-transfer in this D-π-D structure molecule could make the non-radiative structure-changed process slow and ineffective, which should be the reason for the high fluorescence quantum yield.

The poly-[2-methoxy, (5-2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) film is investigated by means of the Multi-Color Photon Echo (MCPE) technique. Under the three-order nonlinear response theory, the reason for the occurrence of the quantum beats in the time domain and the relations among signal wavevector, pulse sequence and response function are discussed. The analysis of the Raman spectrum of MEH-PPV and the fast Fourier transformation (FFT) results of photon echo (PE) signal dynamics demonstrate the coherent coupling between the C=C bonds and the CC-H bonds and the coherent coupling between the C-C stretching of the phenyl group and the C=C stretching of the vinylene group.