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The study of singlet oxygen generation in AOT micelles containing Spruce Cone from Picea Abies extract was carried out in visible and near IR spectral range. The microemulsion solution with extract appeared to have absorption peak at ∼300 nm and luminescence peaks within 680÷720 nm wavelength range. Taking into account the experimental data of steady and time-resolved fluorescence spectroscopy, the possibility of reactive oxygen forms generation in the microemulsion with the extract has been proved. The energy deactivation rate constants in the contact complex after photoexcitation under triplet states quenching of the extract molecules have been determined. [ABSTRACT FROM AUTHOR]

Here, we report the ultrafast carrier dynamics of stripe-type charge ordered manganite Pr0.5Sr0.5MnO3 (PSMO) thin film investigated by time-resolved terahertz spectroscopy. Thin film of PSMO of thickness 150 nm was prepared by using pulsed laser deposition technique. A typical bi-exponential behaviour along with superimposed coherent acoustic modulation was found. Two fast and slow relaxation time constants were obtained. Both the relaxation time constants decrease with increase in optical pump fluence. The acoustic modulation becomes more prominent as the optical pump fluence increases, since the electronic temperature increases which increases the lattice temperature through electron-phonon thermalization and thus, the acoustic modulation strengthens with increase in optical pump fluence. [ABSTRACT FROM AUTHOR]

Wedge-shaped c-GaN nanowall networks grown on c-sapphire substrates are found to show significant blue shift and broadening of the band-edge feature in photoluminescence (PL) spectra. Electron mobility in these structures has also been estimated to be much higher than the theoretical mobility limit in GaN for the same concentration of electrons. These findings suggest quantum confinement of the electrons in the system. Such a confinement has been theoretically explained in terms of the accumulation of negative polarization charges at the inclined facets of the nanowedges that force the free electrons in the conduction band to assemble at the central vertical plane of the structure. If such a triangular confining potential at all exists, the carrier recombination rate is expected to be reduced due to the movement of the photogenerated electrons and holes in opposite directions. Here, we have carried out time-resolved photoluminescence measurements at different transition energy points on a nanowedge-network and a continuous c-GaN epitaxial film grown on c-sapphire substrates. Our study reveals slower PL decay time for the network sample as compared to the continuous film that supports the theoretical model. [ABSTRACT FROM AUTHOR]

The muon collider offers a great discover potential for the future of high energy physics. Indeed, it combines the advantages of a lepton collider, with clean signatures and maximum available center of mass energy, with those of a hadron collider, such as low synchrotron radiation. However, it poses interesting challenges, manly related to the fact that muons decay and their product interact with the material of the machine producing the socalled Beam-induced-Background. For this reason, a careful design of the experiments running at a muon collider must be performed, starting from simulation, and moving to the R&D on dedicated technologies. This contribution will focus on the muon system of a muon collider experiment: the current design limitations will be presented, together with the alternative solutions that are being considered. In particular, we are proposing to use the Picosec Micromegas technology for a dedicated timing layer in the muon system, which will improve the muon reconstruction performance in that region. The R&D on this technology will be discussed and preliminary results will be presented. [ABSTRACT FROM AUTHOR]

At room temperature rotational reorientation dynamics of 3,3'-NBC-Onehas been studied in polar protic solvents using picosecond time resolved spectroscopy.Experimental rotational reorientationtime shows 3,3'-NBC-Onerotates slower when viscosity of solvent increases. Qualitative analysis using Stokes-Einstein-Debye (SED), Geirer-Wirtz (GW) and Dote-Kivelson-Schwartz (DKS)mechanical frictions theories has been performed. The measured reorientation times of 3,3'-NBC-One is in close agreement with slip boundary condition as predicted by SED theory. [ABSTRACT FROM AUTHOR]

Rotational reorientation dynamics of NMBHC-2-One has been studied in ethanol and octanol solvents by varying temperature using picosecond time-resolved spectroscopy. Experimental rotational reorientation time shows NMBHC-2-One experiences higher friction in octanol than ethanol. Qualitative analysis using SED, GW, and DKS mechanical frictions theories has been performed. The theoretical measured reorientation times of NMBHC-2-One fails to explain the observed experimental values, it enables us to test dielectric friction theories. [ABSTRACT FROM AUTHOR]

This paper describes the surfactant-assisted synthesis of ZnSe nanoparticles by the hydrothermal method. In this route, zinc salt, sodium selenite (Na2SeO3) are used as zinc and selenium precursors. The reaction is performed in the presence of 0.1 M cetyl trimethyl ammonium bromide (CTAB) as a surfactant and hydrazine hydrate (N2H4.H2O) as a reducing agent. The effect of change in zinc salt on size, morphology and optical properties of ZnSe nanocrystals have been investigated by performing the reaction at 150 °C for 8hrs. The phase structures, morphologies and optical properties of synthesized ZnSe nanoparticles were characterized by using X-ray diffraction (XRD), Ultraviolet-visible spectroscopy (UV-vis), Field emission scanning electron microscopy (FESEM), Photoluminescence (PL) spectroscopy and Time-resolved photoluminescence spectroscopy (TRPL). The XRD analysis shows a successful synthesis of small-sized (8-11 nm) crystalline ZnSe nanoparticles. Zinc acetate has been found to be the favourable source of zinc for the synthesis of pure ZnSe nanoparticles under mentioned reaction conditions. In this study, it has been found that the Zn source used during the reaction has a considerable effect on structural, morphological, and optical properties of synthesized ZnSe nanoparticles. Investigations done in the presented work can be helpful for the controlled morphological synthesis of ZnSe nanoparticles with better purity for various applications. [ABSTRACT FROM AUTHOR]

Natural supramolecular complexes gain much attention of researches at nature-Like and biotechnologies due to their incomparably high efficiency. Cyanobacteria, as the ancient photosynthetic microorganisms, have a perfect mechanism for harvesting and converting solar energy. The effectiveness of their light-harvesting complex is near unity and exhibit multifarious self-fluorescent properties. The last intrinsic natural feature is essential for the fluorescent non- destructive analysis of the structure and functioning of supramolecular pigment-protein complexes on a single-cell level and gives a unique opportunity for steady-state and time-resolved investigations of living cyanobacterial cells in vivo. In this work, the advanced methods of fluorescent spectroscopy (i.e. confocal microscopic spectroscopy and excitation- emission fluorescence spectroscopy) are used to study natural pigment-protein complexes in connection with their possible application in biosensorics and green energy production. [ABSTRACT FROM AUTHOR]

In this work, bismuth oxide (Bi2O3) photocatalyst was prepared using nitrates of bismuth through a single step microwave method. These Bi2O3 photocatalysts were analysed by using various techniques such as XRD, Raman, UV-Vis spectroscopy and time resolved photoluminescence (TRPL) life time measurements. The Bi2O3 photocatalyst was formed with tetragonal structure in the as-prepared form and it was structurally transformed into a monoclinic phase with appropriate heat-treatment at 550 ᵒC. This was noticed as a phase transformation from β-phase (tetragonal) to α-phase (monoclinic structure) which has been confirmed by XRD and Raman spectroscopy analysis. The synthesized Bi2O3 photocatalyst with monoclinic phase was tested for the photocatalytic degradation of Rhodamine B (Rh-B) under Sun light irradiation and the results are discussed in this paper. [ABSTRACT FROM AUTHOR]

At the room temperature rotational re-orientations times of the probe DMMN have been studied in alcohol series, by using the Steady-State Fluorescence Depolarisation and Time-Correlated Single Photon Counting (TCSPC) techniques. Experimental observation shows DMMNprobe rotates slower when solvent viscosity increases. SED stick boundary conditions matches nearly with the experimental values for lower alcohols. Quasi-hydrodynamic models (Dote-Kivelson-Schwartz and Geirer-Wirtz) were used to determine mechanical friction and found an interesting behaviour towards super stick trend. [ABSTRACT FROM AUTHOR]

We study the laser cooling of atoms with a narrow-line optical transition in monochromatic laser light, i.e. in regimes of quantum nature of laser-light interactions resulting in a significant recoil effect. It is demonstrated that a minimum laser cooling temperature for two-level atom in standing wave reached for red detuning close to 3 recoil frequency, greatly different from the theory used for a semiclassical description of Doppler cooling. A set of dimensionless parameters uniquely characterizing the time evolution and the steady state of different atoms with narrow-line optical transitions in the laser field is introduced. The results can be used for analysis of optimal conditions for laser cooling of atoms with narrow lines such as Ca, S r, and Mg, which are of great interest for atomic clocks. [ABSTRACT FROM AUTHOR]

Brilliant synchrotron radiation (SR) has enabled us to investigate fast phenomena even in small samples. At the same instance, the property of sample may be affected by the SR due to the high brilliance. An SR X-ray pump and optical probe measurement has then been performed at a storage ring facility of SPring-8 to investigate the spectral change in the near infrared region of a GaAs single crystal irradiated by an intense X-ray pulsed SR beam with a photon energy of just above the K-edge of As. The transient transmission spectrum was monitored by using a broadband optical pulsed beam and a dispersive spectrometer. We obtained the spectral profile change with a response time of shorter than the pulse duration of SR. The spectrum shows the abrupt change in transmittance at around 880 nm corresponding to the band gap energy of GaAs, and the fringe on the spectrum originated from the interference at the sample with a thickness of about 10μm. The band gap energy and the fringe shift to the opposite direction to each other, the behavior of which is explained to be due to the band gap shrinkage accompanied with the decrease of refraction index originated from the free carriers. The transient band gap shrinkage suggests the nonthermal lattice distortion induced by SR irradiation. [ABSTRACT FROM AUTHOR]

The layout and the characteristics of the Quick scanning EXAFS (QEXAFS, ref. [1]) setup at beamline P64 at the storage ring PETRA III, DESY, Germany are described. The quickly oscillating cryo-cooled monochromator allows measurements from 4.5 keV to 44 keV with frequencies up to 100 Hz. The effect of tapering of the undulator on spectra as well as the different detection schemes with transmission, reflectivity and fluorescence are discussed. The data acquisition is explained in detail. Reference spectra at different frequencies and examples of time resolved user experiments are shown. The influence of noise and filtering on the spectra is analysed. [ABSTRACT FROM AUTHOR]

We present the outlines of a new microcontroller based data acquisition system which is aimed for reliable operation in a typical cosmic ray particle registration experiment. The system supports connection of up to 16 input signals and ensures the following operation functionality: (1) stable monitoring of the intensity of a digital pulse signal, or digitization of a continuous potential level with a low time resolution (typically, about 1 s-100 s); (2) registration of uninterruptable high-resolution (up to 5-10μs) time series of the input signal intensity; (3) synchronization of registered time series with both external (physical) or local (programbased) trigger signal; (4) possibility of an on-the-fly change of the whole configuration of informational system (both the combination and type of input signals, time resolution and sum duration of the time series measurements, trigger logic, etc.) immediately in operation time through convenient communication by plain text messages in dialog mode. In particular, the considered system is applied now for a long-term, high precision measurement of the counting rate of neutron signals at the NM64 type neutron supermonitor of the Tien Shan mountain cosmic ray station, with a real-time representation of the whole collected dataset in a WWW database. [ABSTRACT FROM AUTHOR]

Silylenes (silanediyls) have made an important impact on organosilicon chemistry even if it is of more recent foundation than carbenes in organic chemistry and much less complete. These species are highly reactive intermediates. They play a central role in the chemical vapour deposition (CVD) of various silicon-containing thin films which have a technological importance in microelectronics as well as in the dry etching processes of silicon wafers. Spectroscopic methods have been developed to observe these species, a necessary pre-requisite to their direct monitoring. In this work, deuterated phenylsilane precursor, PhSiD3 was chosen for SiD2 because its analogue phenylsilane, PhSiH3 proved to be a good precursor for SiH2 and the high quality decay signals observed revealed that SiD2 be readily detected from PhSiD3 and that if other decomposition pathways (e.g. PhSiD + D2) are occurring, they do not effect measurements of the rate constants for SiD2. The absorption spectrum of SiD2 formed from the flash photolysis of a mixture of PhSiD3 and SF6 at 193nm were found in the region 17384-17391 cm-1 with strong band at 17387.07 cm-1. This single rotational line of pQ1 was chosen to monitor SiD2 removal. Time-resolved studies of SiD2 have been carried out to obtain rate constants for its bimolecular reactions with D2. The reactions were studied over the pressure range 5-100 Torr (in SF6 bath gas) at four temperatures in the range 298-498K. Single decay from 10 photolysis laser shots were averaged and found to give reasonable first-order kinetics fits. Second order kinetics were obtained by pressure dependence of the pseudo first order decay constants and substance D2 pressures within experimental error. The reaction was found to be weakly pressure dependent at all temperatures, consistent with a third-body mediated association process. In addition, SiH2+ H2 reaction is approximately ca. 60% faster than SiD2+D2 reaction. Theoretical extrapolations (using Lindemann-Hinshelwood model and Rice, Ramsperger, Kassel and Marcus (RRKM) theory) were also carried out and obtained data fitted the Arrhenius equations. [ABSTRACT FROM AUTHOR]

This article gives a brief review of experimental studies of hydrogen Balmer series emission spectra. Ongoing research aims to evaluate early plasma evolution following optical breakdown in laboratory air. Of interest is as well laser ablation of metallic titanium and characterization of plasma evolution. Emission of titanium monoxide is discussed together with modeling of diatomic spectra to infer temperature. The behavior of titanium particles in plasma draws research interests ranging from the modeling of stellar atmospheres to the enhancement of thin film production via pulsed laser deposition. [ABSTRACT FROM AUTHOR]

We have directly determined the intramolecular electron transfer rate and revealed its mechanism in supramolecular complexes during CO2 photoreduction by time-resolved infrared spectroscopic measurements over a wide temporal range. [ABSTRACT FROM AUTHOR]

We theoretically examine time-resolved diffraction from molecules which undergo non-adiabatic dynamics and identify contributions from inelastic scattering that indicate the presence of an avoided crossing and the corresponding nuclear configuration. [ABSTRACT FROM AUTHOR]

We use time-resolved photoelectron spectroscopy with wavelength-selected XUV femtosecond pulses to study photoinduced dynamics of organic molecules in solutions at millimolar concentrations. Upon electronic excitation we observe relaxation processes, such as excited state intramolecular proton transfer and trans-cis isomerization. [ABSTRACT FROM AUTHOR]

The formation of nitrous acid (HONO) through photolysis of o-nitrophenol was captured in real time by time-resolved photoelectron spectroscopy using single-order high harmonic probe pulses. HONO is released 250 fs after photoexcitation. [ABSTRACT FROM AUTHOR]

To explore nitric oxide (NO)-donating capability of Roussin's red ester [Fe2(μ-RS)2(NO)4] (RRE), photodissociation of NO from RRE and its subsequent reaction dynamics were probed by monitoring the N–O stretching mode after excitation with a 400-nm photon. As a result of the experiment, the NO generation quantum yield was obtained. [ABSTRACT FROM AUTHOR]

We report, to the best of our knowledge, the first time-resolved high-harmonic spectroscopy (TR-HHS) study of a chemical bond rearrangement. We investigate the transient change of the high-harmonic signal from 1,3-cyclohexadiene (CHD), which undergoes ring-opening and isomerizes to 1,3,5-hexatriene (HT) upon photoexcitation. By associating the variation in the harmonic yield to the changes in the electronic state and vibrational frequencies of the molecule due to isomerization, we find that the CHD excited via two-photon absorption of 3.1 eV photons isomerizes to HT, i.e., ring-opening occurs, around 400 fs after the excitation. The present results demonstrate that TR-HHS, which can track both electronic and nuclear dynamics, is a powerful tool for studying ultrafast photochemical reactions. [ABSTRACT FROM AUTHOR]

We present time-resolved coincidence imaging of F2− photodissociation by 400nm and intense 800nm ultrafast pulses. Coincidence fragment imaging reveals parallel and perpendicular single photon dissociation on 2Σg+ and 2πg states, and additional intense-field dissociation features. [ABSTRACT FROM AUTHOR]

The wave guiding feature of the optical fibre optical fibres is specifically exploited to construct a novel type of electron gun to realize single-shot low-energy electron diffraction experiments with the sub-picosecond resolution for studying irreversible samples. [ABSTRACT FROM AUTHOR]

Time-dependent Schrodinger equation simulations for a one-dimensional model potential reveal that the delay extracted from a streaking spectrogram does not reflect the photoemission time if the streaking field inside the solid cannot be neglected. [ABSTRACT FROM AUTHOR]

We have shown that the spectral position of Tamm plasmon resonance can be efficiently manipulated on a picosecond time scale by the photoinduced change in metal complex permittivity. Time-resolved spectroscopy of a gold/photonic crystal sample reflectance has shown that magnitude of the reflectance modulation in the sample is 20-fold enhanced in comparison with a bare gold film. By proper selection of the probe frequency, a 200-fs long reflectance modulation was observed. [ABSTRACT FROM AUTHOR]

A computer-controlled flow setup has been designed and implemented at the Energy Dispersive EXAFS beamline (BL-08) at INDUS-2 SRS which facilitates in situ time-resolved X-ray Absorption Spectroscopy (XAS) measurements on reactions carried out under specialized experimental conditions. The set-up has been tested by in-situ time resolved X-ray near edge structure (XANES) measurement on the evolution of the reduction process during synthesis of Cu nanoparticles under N2 ambient by reducing Cu(II) Acetate precursor with NaBH4. [ABSTRACT FROM AUTHOR]

We present an experimental characterization of the evolution dynamics of CI and CII lines in an ultrafast laser produced graphite plasma under various ambient conditions. Fast and slow components are observed in the temporal evolution of CI transition at 658.7 nm (3p¹P - 4d¹P0) and CII transition at 426.7 nm (3d²D - 4f ²F0). Fast peak is due to the recombination of fast ions species with electrons, found to have an increase in velocity upon increasing the ambient pressure. Whereas the slow peaks in both cases can be the results of slow ions or slow neutrals in the plume. [ABSTRACT FROM AUTHOR]

Time resolved photoluminescence investigation in air and in vacuum atmosphere of the visible luminescence related to silica surface defects is here reported. Two contributions can be singled out: one, observed both in air and in vacuum, is the well-known blue band, peaked around 2.8 eV decaying in ns; the other, only observed in vacuum, is a structured emission in the violet range characterized by two vibronic progressions spaced 1370 cm-1 and 360 cm-1 decaying in ~100 ns. In contrast with previous attribution, the well distinguishable spectroscopic properties together with the observation of the effects induced by the interaction with nitrogen allow to state that the emission bands originate by two different defects. [ABSTRACT FROM AUTHOR]

Sol-gel silica thin films embedding an ytterbium quinolinolato complex (YbClQ4) have been obtained using different alkoxides. Homogeneous, crack- and defect-free thin films of optical quality have been successfully deposited on glass substrate by dip-coating. The silica thin films have been characterized by time-resolved photoluminescence. The luminescence properties of the YbClQ4 are preserved in silica films prepared through an optimized sol-gel approach. The excited state lifetime of the lanthanide is comparable to those observed in bulk and longer than the corresponding ones in solution. [ABSTRACT FROM AUTHOR]

Time-resolved photoelectron spectroscopy is a well established method of femtosecond spectroscopy able to reveal ultrafast electronic relaxation by a significant change of the photoionization channel as a function of the delay. Otherwise femtosecond photoexcitation often involves multiphoton ionization. This paper illustrates a singular two-photon ionization process insensitive to vibrational energy and involving ubiquitous doubly excited states encountered at high energy just below the ionization potential (IP). The population of these multielectronic excited states decays via an Auger-like process to a set of Rydberg states. This fast and efficient internal conversion takes place within the probe duration such that the Rydberg states can be photoionized by the absorption of a subsequent probe photon. The photoelectron spectrum is then characterized by a Rydberg fingerprint. This process will be illusrated in azulene, methyl iodine and nitrogen dioxide. [ABSTRACT FROM AUTHOR]

When focusing an ultrashort laser pulse inside a transparent material, a permanent alteration of the (complex) refractive index takes place in the irradiated region. In the tight focusing regime, a precise control over the energy deposition can be achieved. Based on this principle, point by point fabrication of embedded microoptical systems has been demonstrated in the bulk of amorphous fused silica (a-SiO2). Although the permanent laser-induced structural changes are starting to be known, the mechanisms underlying material modification are not completely understood. A widely accepted scenario of the laser-matter interaction still has to be elaborated. Specifically, the identification and the relative importance of localized and delocalized energy relaxation channels are under debate. The laser energy is coupled into the material through free carriers generated via photoionization mechanisms. Our goal is to study the energy transfer from the free carriers to the bulky material by measuring the time-resolved absorption in the interaction region. Our setup, based on an optical microscope employed in a pump-probe scheme, allows for time-resolved imaging of the interaction region with a temporal resolution about 300 fs and a spatial resolution of 650 nm. By processing ultrafast photographs of the laser generated electron-hole plasma, we are able to monitor the absorbance in-situ. We present results obtained with two illumination probe wavelengths at 400 nm and 800 nm. The time span covered ranges from the very first moments of the laser-matter interaction up to 1 ns. We observe that the absorption kinetics is not homogeneous over the irradiated volume and depends strongly on the initial distribution of laser energy. We propose a correlation of the observed absorption with the creation and decay of optically active defects. [ABSTRACT FROM AUTHOR]

We report on time resolved differential transmission experiments to provide insight into both the time scales and the nature of the microscopic interactions and carrier dynamics in MOVPE grown ferromagnetic InMnAs and InMnSb. Theoretical calculations of the electronic structure for InMnAs are performed using an 8 band k·p model which includes non-parabolicity of the conduction bands; strong band-mixing of the valence bands; as well as coupling of Mn impurities to the electrons and holes. Our preliminary theoretical results explain the sign change in the differential transmission signal as a function of probe wavelength. [ABSTRACT FROM AUTHOR]

Time-resolved force sensing technique was applied to the study of propulsive characteristics of water droplets for multi-pulse TEA (transversely excited at atmospheric pressure) CO2 laser propulsion. Laser-driven blast waves and associated flow dynamics in the impulse generation processes of ablation of water droplets were studied by Schlieren visualization. Experimental results showed that coupling coefficient and specific impulse decreased as the interval between laser pulses and pulse numbers was increased. The maximum speed of the blast wave in the opposite and same direction of laser propagation was respectively 10 km/s and 7 km/s. [ABSTRACT FROM AUTHOR]

Time-resolved particle image velocimetry is used to measure the flow field behind orifice in a circular pipe, several large-scale fluctuating structures are extracted by means of proper orthogonal decomposition. It is shown that 'vertical flapping'and 'compression and expansion' are the two most dominant fluctuating structures behind orifice. Comparison of the vertical central plane of the compression and expansion eigenmode and the peak position of the mass transfer coefficient points strongly suggests that the large-scale compression and expansion fluctuating structure dominatesthe peak position of the mass transfer coefficients. [ABSTRACT FROM AUTHOR]

Most of the known transiting extrasolar planets orbit slowly rotating F, G or K stars. In here we report on the detection of a transiting planet orbiting the bright, rapidly rotating A5 star HD15082 (WASP-33b, V = 8.3, m sin i = 86 kms-1), recently made by SuperWASP. Time resolved spectroscopic observations taken during transit show a hump caused by the planet crossing the line profile. From the analysis of the spectra, we derive the radius of the planet and find that it is orbiting retrograde in respect to the spin of the star. Because of its small distance from an A5 star (the orbital period of only 1.22 days), the equilibrium temperature of the planet is estimated to be 2700 K. The planet thus is one of the hottest planets known, which makes it relatively easy to detect it in the IR. We thus tried to detect it using the TNG but did not succeed. [ABSTRACT FROM AUTHOR]

The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars with massive compact companions like massive white dwarfs (M>1.0 M⊙), neutron stars or stellar mass black holes. The existence of such systems is predicted by binary evolution theory and recent discoveries indicate that they exist in our Galaxy. We classified about 1500 hot subdwarf stars from the Sloan Digital Sky Survey (SDSS) by colour selection and visual inspection of their spectra. Stars with high velocities have been reobserved and individual SDSS spectra have been analysed. In total ≃170 radial velocity variable subdwarfs have been discovered and ≃80 of them have been selected as good candidates for follow-up time resolved spectroscopy to derive their orbital parameters. Up to now we found seven close binary sdBs with short orbital periods ranging from ≃0.21 d to 1.5 d. In our photometric follow-up campaign we discovered two eclipsing binaries with companions, that are more most likely substellar. [ABSTRACT FROM AUTHOR]

We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts (GRBs), which contains 476 bursts detected by the BAT between 2004 December 19 and 2009 December 21. This catalog presents burst trigger time, location, 90% error radius, duration, fluence, peak flux, time-averaged spectral parameters and time-resolved spectral parameters measured by the BAT. The BAT T90 duration peaks at 70 s. We confirm that the spectra of the BAT short-duration GRBs are generally harder than those of the long-duration GRBs. The observed durations of the BAT high redshift GRBs are not systematically longer than those of the moderate redshift GRBs. Furthermore, the observed spectra of the BAT high redshift GRBs are similar to or harder than the moderate redshift GRBs. [ABSTRACT FROM AUTHOR]

We investigated the dynamic process of an expanding femtosecond laser ablation plume of aluminum generated in an irradiation intensity range of 1013-1015 W/cm2 with the ultrafast x-ray absorption fine structure (XAFS) imaging technique. The XAFS spectra of the aluminum LII,III edge of the plume revealed that the plume consists of doubly and singly charged ions, neutral atoms, liquid particles, and possible atomic clusters. Scanning electron microscopy of deposited ablation particles confirmed that the liquid particles corresponds to the spherical nanoparticles with a size ranging from several tens nanometers to approximately 200 nm. The spatiotemporal evolution of the XAFS image of the plume shows the sequential appearance of each ablation particle from aluminum surface according to its ejection velocity. The result suggests that the photomechanical fragmentation process, which was theoretically proposed, is dominant mechanism for the nanoparticle ejection under the irradiation intensity far from the ablation threshold of aluminum. This study clearly demonstrates the potential of our technique for measuring the ultrafast dynamics of femtosecond laser ablation process. [ABSTRACT FROM AUTHOR]

We study experimentally the electronic excitation mechanisms involved in the breakdown and ablation of wide band gap dielectric materials. We use a femtosecond pump-probe interferometry technique to measure the density of carriers which is excited by ultrashort intense laser pulses. In Al2O3, we observe a density dependent lifetime for electron hole pairs excited by the light pulse, indicating second order or bimolecular recombination kinetics. Then, we use a sequence of two excitation pulses: a first short pulse at 400 nm excites a large density of carriers, and a second one at 800 nm with different pulse duration, namely 50 fs and 10 ps, reaches an excited solid. The intensity of each pulse is kept just below the damage threshold, which is surpassed when both pulses are impinging the sample. We show that the total density of carriers is just the sum of the density excited by the two pulses sent independently. The interpretation of this result leads us to conclude that the second pulse deposit further energy in the material by heating the previously excited carriers, without inducing any electronic excitation itself. This seems to demonstrate that the avalanche process, which is often invoked in the laser breakdown literature, does not play any role in our experimental conditions. [ABSTRACT FROM AUTHOR]

The structural dynamics of short-pulse laser irradiated surfaces and nano-structures has been studied with nm spatial and ultrafast temporal resolution by means of single-shot coherent XUV-scattering techniques. The experiments allowed us to time-resolve the formation of laser-induced periodic surface structures, and to follow the expansion and disintegration of nano-objects during laser ablation. [ABSTRACT FROM AUTHOR]

We apply ultrafast time-resolved X-ray diffraction to directly study coherent acoustic and optical phonons in laser-excited materials. In Au the ps acoustic response has been investigated with the particular goal to clarify the interplay of electronic and thermal pressure contributions. In Bi the extreme softening of the coherently excited A1g optical phonon presents strong indication that upon intense laser-excitation the Peierls-transition which determines the equilibrium structure of Bi can be reversed. In FeRh we studied the lattice response after a fast laser-induced anti-ferromagnetic to ferromagnetic phase transition. [ABSTRACT FROM AUTHOR]

A fast coaxial electrical discharge, with relatively low current, was used to produce a Z-pinch effect in a laser produced aluminum plasma. The ion flux in the laser plasma was monitored with a Langmuir ion probe. The line density in the plasma column was controlled by using an aperture to select the portion of the laser plasma which enters the discharge cell. The Z-pinch dynamics were recorded using time-resolved imaging of the visible self-emission; the plasma was pinched to about one-third of the initial radius. Both the laser and Z-pinch plasmas were diagnosed using time-and space-resolved spectroscopy; substantial heating was observed. The measured behaviour of the pinch was compared with predictions of the slug model. [ABSTRACT FROM AUTHOR]

This contribution investigates laser-induced damage of thin film and bulk polymer samples, with the focus on physical processes occurring close to the damage threshold. In-situ real-time reflectivity (RTR) measurements with picosecond (ps) and nanosecond (ns) temporal resolution were performed on thin polymer films on a timescale up to a few microseconds (μs). A model for polymer thin film damage is presented, indicating that irreversible chemical modification processes take place already below the fluence threshold for macroscopic damage. On dye-doped bulk polymer filters (as used for laser goggles), transmission studies using fs-and ps-laser pulses reveal the optical saturation behavior of the material and its relation to the threshold of permanent damage. Implications of the sub-threshold processes for laser safety applications will be discussed for thin film and bulk polymer damage. [ABSTRACT FROM AUTHOR]

The material modification in the volume of transparent dielectrics using tightly focused fs-laser radiation is an important topic for many research groups all over the world. A wide range of applications like the writing of waveguides, micro-structuring by material modification and subsequent etching, or the micro-welding of glass is based on the localized melting and quenching in a different state. Time-resolved white-light interferometry is adopted for the measurement of the optical phase changes in processed materials. A modified Mach-Zehnder interferometer setup combined with microscope objectives is used. The white light is generated by focusing ultrafast laser radiation (tp = 80 fs) in a sapphire crystal using a micro-lens array to minimize temporal and spatial fluctuations in the white-light continuum. Lateral and coaxial pump-probe measurements of the phase changes during material processing are performed using one or two coupled ultrafast laser sources at different repetition rates (frep = 1 kHz-1 MHz) or by adopting single pulses. The temporal delay between the pump and the probe can be adjusted in the range τ<=1.8 μs in dependence on the repetition rate of the pump radiation. The optical phase shift and therefore the refractive index of the material is calculated from the interference images. The knowledge of the refractive index during the modification process with a temporal resolution in the ps-range and a spatial resolution of several microns leads to a better understanding of the initial processes for the permanent material modifications. [ABSTRACT FROM AUTHOR]

Elementary processes of two-dimensional (2D) turbulence has been examined by extensive analyses of fine-scale structures in the density distribution of a magnetized pure electron plasma that evolves from an unstable initial state to a single-peaked stable distribution through successive mergers of vortex patches. The observed vortex dynamics in the real space corresponds to the spectral dynamics analyzed in the wave-number (k) space. Along with the merging process among patches, the energy spectrum E(k) broadens upward and its shape shows a power-law scaling k-α with α>3 in a wide wave-number region above kin j corresponding to the size of the first generated patches. From the energy and enstrophy tranfer rate evaluated from the time-resolved spectra, it has been observed that the enstrophy cascades at a constant transfer rate in the region k>3kin j, while the energy is transferred downward at kinj. This spectral dynamics is qualitatively consistent with the theoretical picture of 2D turbulence with discrepancies that the power index of E(k) is larger than the theoretical prediction of α = 3 and the enstrophy transfer rate is almost zero around kin j reflecting the effect of coherent vortices. [ABSTRACT FROM AUTHOR]

A simple, compact, point-focusing spatial filter for x-ray fluorescence is presented. This construction maintains the large solid angle and directionality of existing designs but is more easily machined. Combined with a selective absorber, it can be used as an x-ray low-pass filter; this is one common approach taken in inelastic x-ray scattering studies and fluorescence spectroscopy. When combined with a scintillation detector, this device forms a large solid angle energy-selective x-ray detector with ns-scale time resolution that is useful for timing studies. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

A time-resolved energy-dispersive XAFS (DXAFS) station has been constructed at the bending magnet beamline BL28B2 at SPring-8 to study the local structural changes of materials during chemical reactions and functional processes. The bending magnet source at SPring-8 has a high photon flux above 50 keV. The purpose of this station is to measure DXAFS spectra in a wide energy range from 7 to 50 keV covering K-edges of lanthanides. Its main components are a polychromator with a bent silicon crystal, a mirror to reject higher harmonics, and a position-sensitive detector (PSD). To correspond to a wide energy range, polychromators for Bragg and Laue geometry were developed for the energy range below and above 12 keV, respectively. The PSD used is CCD coupled with a fluorescent screen and lens system. The fluorescent materials and their thickness were optimized for measurement in the x-ray range. Good quality spectra of Ce K-edge (40.5 keV) were obtained with exposures of 360 ms for the standard samples. The present status of the system and some experimental examples are presented in this report. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Experimental system for the time- and angle-resolved photoemission spectroscopy have been constructed at BL13 in SAGA Light Source, in order to study the electronic non-equilibrium in the surface layer of laser-excited materials The experimental system is very useful for photoemission spectroscopy in the wide temporal and angular ranges. The time- and angle-resolved photoemission spectra can be obtained with using the gate electronics for the MCP detector of the photoemission spectrometer. The gated MCP detector is synchronized with the laser pulse from Ti:sapphire regenerative amplifier with the repetition frequency of 10 to 300 kHz. The time-window of the gated MCP detector can be changed between 10 nano- and 160 micro-second. The time-resolved measurement in pico-second region can be performed with using the pump-probe technique which uses fundamental, second and third harmonics from the Ti:sapphire laser as the excitation source. Using these systems, we can perform the time- and angle-resolved photoemission study for various photo-excited phenomena and surface dynamics. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]