... Accession Number : ADA520381. Title : Remote Femtosecond Laser Induced Breakdown Spectroscopy (LIBS) in a Standoff Detection Regime. ...
DTIC Science & Technology
... Title : Optoelectronic Workshops (10th). Femtosecond Time-Resolved Spectroscopy. ... The research in ultrafast time-resolved spectroscopy. ...
... Accession Number : ADA341311. Title : DURIP97 Femtosecond Vibrational Spectroscopy of Shock Waves in Materials. Descriptive Note : Final rept. ...
The authors have studied the dynamics of ultrafast internal conversion processes using femtosecond time-resolved photoionization and photoelectron spectroscopy. In hexatriene, following femtosecond pulse excitation at 250 nm, they use time-delayed photoio...
National Technical Information Service (NTIS)
... Title : Effects of N2-CO Polarization Beating on Femtosecond coherent Anti-stokes Raman Scattering Spectroscopy of N2 (POSTPRINT). ...
... Title : Compact Femtosecond Pulse Approach to Explosives Detection Combining InN-Based Time Domain Terahertz Spectroscopy and Laser ...
This grant provided partial funding for the acquisition of a powerful femtosecond laser. The laser is to be used in making femtosecond time resolved measurements of shock waves in molecular materials, with the eventual application being understanding the ...
The recent realization of femtosecond-resolved fluorescence spectroscopy in the UV region has led to important new results for a number of fundamental processes in the chemistry of liquids, such as transient solvation and ultra-fast intramolecular electro...
A new experimental technique for the time-resolved study of anion reactions is presented. Using femtosecond laser pulses, which provide extremely fast (approximately 100 fs) time resolution, in conjunction with photoelectron spectroscopy, which reveals di...
We develop a polarization-sensitive femtosecond pump probe technique, Raman induced polarization spectroscopy (RIPS), to study coherent rotation in molecular fluids. By observing the collisional dephasing of the coherently prepared rotational states, we a...
... breakdown spectroscopy offers advantages for detecting trace explosive residues ... of the femtosecond pulse for, explosive residue detection. ...
... HIGH INTENSITY ULTRAFAST LASER INTERACTION FEASIBILITY STUDY OF LASER INDUCED BREAKDOWN; SPECTROSCOPY (LIBS) IN ...
... diffraction to determine structural dynamics of excited states and reaction products of isolated aromatic carbonyls, acetophenone and benzaldehyde ...
We investigate the time dynamics of a four-level rubidium atomic system excited by a train of 0? pulses. Resonant 0? pulse shaping is achieved by propagation of weak femtosecond pulses through rubidium vapor and characterized using frequency-resolved optical gating and within the linear dispersion theory. The excitation of the Rb atoms by 0? pulse train is studied ...
NASA Astrophysics Data System (ADS)
The irreversible photoconversion of T203V green fluorescent protein (GFP) via decarboxylation is studied under femtosecond excitation using an accumulative product detection method that allows us to measure small conversion efficiencies of down to ?OD = 10?7 absorbance change per pulse. Power studies with 800- and 400-nm pulse ...
PubMed Central
We present a theory of time-resolved emission spectroscopy in the femtosecond region. It is shown that a femtosecond time-resolved emission spectrum consists of the contributions from the population and coherence of the system. Theoretical expressions for describing femtosecond time-resolved emission molecular ...
Energy Citations Database
We present the first femtosecond soft x-ray spectroscopy in liquids, enabling the observation of changes in hydrogen bond structures in water via core-hole excitation. The oxygen K-edge of vibrationally excited water is probed with femtosecond soft x-ray ...
to significant ad- vances in solid-state laser technology.3 Many new physical processes emerge during femtosecond ablative material removal processes are not well understood. Titanium-based thin films possess manyTime-of-flight and emission spectroscopy study of femtosecond laser ablation of titanium Mengqi Ye
E-print Network
The ultrashort pulse x-ray source developed at the Advanced Light Source at the Lawrence Berkeley Laboratory is based on electron slicing in storage rings, and generates (approx)100 femtosecond pulses of synchrotron radiation spanning wavelengths from the...
Self-channeling properties of high intensity laser pulses are used to extend spectroscopic methods as LIBS to standoff. This work shows the advantages of using selfchanneled femtosecond pulses in Laser-Induced Breakdown Spectroscopy of polymeric micromete...
High resolution photoemission was used in combination with supersonic molecular beam techniques to study the spectroscopy and femtosecond intramolecular dynamics of several molecular ions in the small polyatomic limit. Internally-cold C sub 2 H sub 2 , C ...
Ultrafast, heterodyne, polarization spectroscopies are used to measure solute-solvent frictional coupling and characterize the neat solvent's relaxation dynamics on femtosecond and picosecond timescales.
Ultrafast, heterodyne, polarization spectroscopies are used to measure solute-solvent frictional coupling and characterize the neat solvent`s relaxation dynamics on femtosecond and picosecond timescales.
Acetic acid ultrafast dynamics were measured using femtosecond optical-Kerr spectroscopy for temperatures ranging from near the melting to boiling points of the liquid.
DOE Information Bridge
We present results on the ultrafast dynamics of pure hydrogen-bonding solvents, obtained using femtosecond Fourier-transform optical-heterodyne-detected, Raman-induced Kerr effect spectroscopy. Solvent systems we have studied include the formamides, water...
The photodissociation dynamics of some alkali halides are explored via the method of femtosecond transition-state spectroscopy (FTS). The alkali halide dissociation reaction is influenced by the interaction between the covalent and the ground state ionic ...
The real time dynamics of wave packet resonance (due to photofragment trapping) in the reaction of sodium iodide is reported using femtosecond transition state spectroscopy (FTS). The observed oscillation frequency and delay give the effective vibrational...
The feasibility of attaining improved explosives detection and identification using complementary InN-based time-domain terahertz spectroscopy (TDTS) and laser-induced breakdown spectroscopy (LIBS) techniques employing 1550-nm femtosecond (fs) pulse techn...
By using femtosecond optical techniques including self-phase modulation, spectral filtering and dispersion compensation, we constructed a tunable multiwavelength synchronized femtosecond light source from a cw modelocked femtosecond Ti:sapphire laser, and experimentally characterized its performance. Synchronized ...
,,Optimization of Laser Induced Breakdown Spectroscopy Using Tailored Femtosecond Laser Pulses" DPG. Englert, C. Sarpe-Tudoran and T. Baumert ,,Optimization of Laser Induced Breakdown Spectroscopy Using and T. Baumert ,,Time-resolved emission spectroscopy of the femtosecond laser-induced ...
An ultrafast spectrometer with a temporal resolution of 20 fs for studying the polarisation wave interference in condensed matter upon resonance excitation by femtosecond laser pulses is described. The transverse relaxation times T{sub 2} < 20 and 50 fs are measured in optical media with considerably different inhomogeneous broadenings. (femtosecond ...
be monitored by measuring the transient absorption spectrum though a probe laser pulse that is variably delayedFemtosecond transient absorption dynamics of close-packed gold nanocrystal monolayer arrays q Sang Femtosecond transient absorption spectroscopy is used to investigate hot electron dynamics of close-packed 6
The possibility of using biaxial nonlinear crystals in the optical converters of femtosecond radiation pulses for laser sounding of the atmosphere has been studied. A method of broadband monitoring of the atmosphere composition using the differential optical absorption spectroscopy technique is described. The results of the numerical simulation of the ...
... III. The Betaines We have studied the direct photoinduced ET of betaine-30 and related molecules by femtosecond pump-probe spectroscopy in the ...
... within this analysis: the probe spectral width determines ... 2, 85 (1989) 3. Femtosecond Spectroscopy of ... Ahmed H. Zewail in: Ultrafast Phenomena VI ...
... Pagination or Media Count : 40. Abstract : Apparatus for performing femtosecond transition-state absorption spectroscopy has been developed. ...
... FD Lucia Jr., R. Harmon, K. McNesby, R. Winkel Jr., A. Miziolek, �Laser-induced breakdown spectroscopy analysis of energetic materials,� App. ...
... 16. Lian, T., Locke, B., Kholodenko, Y. & Hochstrasser, RM Energy flow solute to solvent probed by femtosecond IR spectroscopy ... 19. Hergt, R. et al. ...
... Ultra-short pulse, high repetition rate Ti ... to use this new laser system with ... Descriptors : *LASERS, *PHOTONS, *MULTICHANNEL, SPECTROSCOPY ...
... 2) Feasibility study of laser induced breakdown spectroscopy (LIBS) in assessment ... not we can reduce the fluence necessary for chemical analysis. ...
Over the first year of this effort considerable attention was devoted to the development of a novel tunable femtosecond source and to the temporal resolution improvement of the electro-optic sampling technique. The technique was applied to the measurement...
The dynamics of the formation of self-trapped excitons (STEs) and Frenkel pairs upon band-gap excitation have been studied in NaCl by femtosecond time-resolved spectroscopy at temperatures ranging from 6 to 330K. We found that the primary yield of Frenkel pairs was governed by the process of exciton relaxation that terminated within 10 ps of excitation for ...
Recently laser-induced breakdown spectroscopy (LIBS) has been investigated as a potential technique for trace explosive detection. Typically LIBS is performed using nanosecond laser pulses. For this work, we have investigated the use of femtosecond laser pulses for explosive residue detection at two different fluences. Femtosecond ...
PubMed
We describe theory and experiment for Fourier-transform sum-frequency surface vibrational spectroscopy using femtosecond lasers and discuss some practical issues in comparing it with the multichannel dispersive sum-frequency generation approach to obtain sub-laser-linewidth resolution in vibrational spectra. A signal-to-noise ratio analysis shows that the ...
Photodissociation dynamics of acetone was investigated for the first time in the gas phase and also in solution by transient absorption and femtosecond stimulated Raman spectrscopy. In the gas phase, a Rydberg state with a decay time of 350 fs, which in solution decays at ~100 fs. In solution. we also found evidence for solvated electron generation. Vibrational information ...
Time-resolved femtosecond coherent anti-Stokes Raman scattering (fs- CARS) spectroscopy of the nitrogen molecule is used for the measurement of temperature in atmospheric-pressure, near-adiabatic, hydrogen-air diffusion flames. The initial frequency-sprea...
We demonstrate fast standoff (>10 m) single-pulse coherent anti-Stokes Raman spectroscopy (CARS), from trace amounts of solids, under ambient light conditions, using phase or amplitude shaped femtosecond pulses.
Femtosecond transient absorption spectroscopy was applied to analyze the mechanism of optical switch of an endo-capped thiophene oligomer with a diarylethene structure as a new class of multimode chemical transducers. The rate of the optical switch of the proconductivity was estimated to be 1.1 ps, corresponding to the formation time of the closed-ring ...
We develop a polarization-sensitive femtosecond pump probe technique, Raman induced polarization spectroscopy (RIPS), to study coherent rotation in molecular fluids. By observing the collisional dephasing of the coherently prepared rotational states, we are able to extract information concerning the effects of molecular interactions on the rotational ...
Ultrafast relaxation kinetics in [beta]-carotene and lycopene has been investigated by femtosecond absorption and fluorescence spectroscopies using tunable excitation pulses. The transient signals induced by the photoexcitation with larger excess energy have broader bands and longer lifetimes both in the excited states. The excess vibrational energy ...
Charge transfer excitation at 640 nm of the cobaltocenium tetracarbonylcobaltate ion pair, (Cp(sub 2)Co(sup +)(vert bar)Co(CO)(sub 4)(sup -)), was monitored in 1,2- dichloroethane solution by femtosecond transient visible absorption spectroscopy. The abso...
The effects of broadband excitation employing femtosecond laser pulses on the coherent anti-Stokes Raman scattering (CARS) spectroscopy of N2 are investigated. We have previously demonstrated that the dephasing rate of the coherence, established by the im...
We present an efficient and robust setup for femtosecond stimulated Raman (FSR) spectroscopy with 60 fs and 10 cm(-1) resolution. Raman pulses of 0.5-5 ps are tunable between 450-750 nm with energies 1-10 ?J. Experimental features of the setup, signal processing, and data treatment are discussed in detail to be readily reproduced in other labs. The setup ...
We present an efficient and robust setup for femtosecond stimulated Raman (FSR) spectroscopy with 60 fs and 10 cm-1 resolution. Raman pulses of 0.5-5 ps are tunable between 450-750 nm with energies1-10 ?J. Experimental features of the setup, signal processing, and data treatment are discussed in detail to be readily reproduced in other labs. The setup is ...
The need for robust, versatile, and rapid analysis standoff detection systems has emerged in response to the increasing threat to homeland security. Laser Induced Breakdown Spectroscopy (LIBS) has emerged as a novel technique that not only resolves issues...
a dynamically deformable jellium with inertia parameters derived from an incom- pressible, irrotational flow of freedom described via a dynamically deformable jellium), allowing for reliable and economical simulations the potential of such experiments as a spectroscopy of cluster shape vibrations. As the jellium description
This paper presents the theoretical background for a synthesis of femtosecond spectroscopy and x-ray diffraction. When a diffraction quality crystal with 0.1�0.3 mm overall dimensions is photoactivated by a femtosecond laser pulse (physical length = 0.3 ?m), the evolution of molecules at separated points in the crystal will not be ...
Ultrashort laser pulses have thus far been used in two distinct modes. In the time domain, the pulses have allowed probing and manipulation of dynamics on a subpicosecond time scale. More recently, phase stabilization has produced optical frequency combs with absolute frequency reference across a broad bandwidth. Here we combine these two applications in a spectroscopic study of rubidium atoms. A ...
We have measured the ultrafast solvent relaxation of liquid ethylene glycol, triacetin, and water by means of femtosecond polarization spectroscopy, using optical-heterodyne-detected Raman-induced Kerr-effect spectroscopy. In the viscous liquids triacetin and ethylene glycol, femtosecond relaxation processes were ...
This paper mainly concerns on nanosecond and femtosecond laser spectroscopy of aromatic organic compounds as neurotransmitters, and plume diagnostics of the ablated species, in order to characterize the plasma dynamics, i.e. the temporal and spatial evolution of the plume. Optical emission spectroscopy has been applied to characterize ...
Heat accumulation by high repetition rate femtosecond laser irradiation inside glass generates a much larger modification than that by a single pulse. In this study, we determined the temperature distribution due to heat accumulation and the characteristic temperature for heat modification inside a soda lime glass by analyzing the ...
The characteristics of femtosecond laser ablation of AlN and Al2O3 for precision microfabrication are studied experimentally. Specifically, the process characteristics during femtosecond laser drilling of microholes with sub-100 ?m diameter are investigated for varying laser parameters and beam path designs for trepanning. The ...
The need for robust, versatile, and rapid analysis standoff detection systems has emerged in response to the increasing threat to homeland security. Laser Induced Breakdown Spectroscopy (LIBS) has emerged as a novel technique that not only resolves issues of versatility, and rapid analysis, but also allows detection in settings not currently possible with existing methods. ...
We present spectra of depleted uranium metal from laser plasmas generated by nanosecond Nd:YAG (1064 nm) and femtosecond Ti:sapphire (800 nm) laser pulses. The latter pulses produce short-lived and relatively cool plasmas in comparison to the longer pulses, and the spectra of neutral uranium atoms appear immediately after excitation. Evidence for nonequilibrium excitation with ...
Possibilities of using superbroadband nonlinear-optical frequency converters for femtosecond laser pulses in lidar sensing of the atmosphere are analyzed. New biaxial nonlinear crystals in which the conditions of phase and group matching can be satisfied simultaneously are basic elements of frequency converters. A technique for the broadband lidar sensing of the gas ...
mechanism for optical atomic clocks. Precision spectroscopy of the hydrogen 1S�2S two-photon resonance has optical atomic clocks which can slice time into a hundred thousand times finer intervals, and which may be realized in atomic spectroscopy and optical atomic clocks. 2. Hydrogen 1S�2S two-photon spectroscopy In our
elemental analysis[14-16]. In this study, we present the combination of laser induced breakdown spectroscopy, Baltimore, MD, USA ABSTRACT Laser Induced Breakdown Spectroscopy (LIBS) by self-channeled femtosecond pulses breakdown spectroscopy, Filamentation, Plasma chemistry 1. INTRODUCTION Self-channeled pulses ...
Under this MURI, research into the use of terahertz spectroscopy, femtosecond laser-induced breakdown spectroscopy, infrared spectroscopy, laser ionization-mass spectrometry and cavity ring-down spectroscopy for explosives detection was pursued. Fundament...
Laser-induced breakdown spectroscopy of copper with a 2 �m thulium fiber laser Matthieu Baudelet; (300.6365) Spectroscopy, laser induced breakdown; (350.5400) Plasmas. References and links 1. J. Debras. Frejafon, and P. Laloi, "Femtosecond time-resolved laser-induced breakdown spectroscopy for detection
We report on measurements of the breaking stress of glass substrates welded with ultrashort laser pulses. Femtosecond laser pulses at repetition rates in the MHz range are focused at the interface between two substrates, resulting in multiphoton absorption and heat accumulation from successive pulses. This leads to local melting and subsequent ...
The angle resolved photoelectron spectroscopy (ARPES) has emerged as a leading technique in identifying static key properties of complex systems such as the electronic band structure of adsorbed molecules, ultrathin quantum-well films or high temperature superconductors. We efficiently combined ARPES by using a two-dimensional analyzer for parallel energy (E) and momentum ...
We review prototype studies in the area of quantum control with femtosecond lasers. We restrict this discussion to atoms and diatomics under gas-phase collision-free conditions to allow for a comparison between theory and experiment. Both the perturbative regime and the nonperturbative regime of the light-matter interaction are addressed. To that end, atomic/molecular beam ...
The authors have studied the dynamics of ultrafast internal conversion processes using femtosecond time-resolved photoionization and photoelectron spectroscopy. In hexatriene, following femtosecond pulse excitation at 250 nm, they use time-delayed photoionization to observe the formation and decay of an intermediate species on the ...
By using the femtosecond optical-heterodyne detected, Raman-induced Kerr effect spectroscopy (OHD-RIKES), we have studied the intermolecular dynamics of toluene, benzyl alcohol, benzonitrile, cyclohexane, and methylcyclohexane in both the time and frequency domains.
Vibrational wave packets in chloroform and gold colloid in chloroform were studied by femtosecond pump-probe spectroscopy. It was found that the main modes of oscillations for both systems coincide with the frequencies of the Raman resonances of chloroform 260 cm-1, 367 cm-1 and 668 cm-1. The effect of gold nanoparticles leads to 4-6 fold increased signal ...
The experimental methodology for structural femtochemistry of reactions is considered. With the extension of femtosecond transition-state spectroscopy to the diffraction regime, it is possible to obtain in a general way the trajectories of chemical reactions (change of internuclear separations with time) on the femtosecond time scale. ...
the temperature dependence of the ampli- tude of the photoinduced reflection, the existence of two gaps is deduced. The femtosecond time-resolved pump-probe technique in- volves the measurement of small photoinduced changes that was without inclusions and was as much as possible single phase. The photoinduced reflectivity measurements
Desorption of Si atoms from Si(111)-(7�7) induced by femtosecond laser excitation has been studied by means of resonance ionization spectroscopy. The desorption yield shows a strong superlinear dependence on the excitation intensity, similar to the case of nanosecond laser excitation, however, femtosecond excitation enhances the ...
of outstanding importance in bioorganic systems. The film properties were tested using X-ray photoelectron-resolved electron spectroscopy utilizing femtosecond soft X-ray pulses is capable of detecting iodine core describe the synthesis of resorcarenes functionalized with iodine marker atoms and their chemical
By using the femtosecond optical-heterodyne detected, Raman-induced Kerr effect spectroscopy (OHD-RIKES), we have studied the intermolecular dynamics of toluene, benzyl alcohol, benzonitrile, cyclohexane, and methylcyclohexane in both the time and frequen...
We present a Fourier-transform spectroscopic technique for investigation of surfaces and interfaces based on IR-visible sum-frequency generation with femtosecond light pulses. The observed spectrum has a resolution that is independent of the input pulse characteristics. (c) 1999 Optical Society of America.
frequency combs. High-finesse, low-dispersion passive optical cavities are used to enhance the power of femtosecond enhancement cavities [5]. These are passive optical cavities with high finesse and low dispersion comb and a high-finesse, low-dispersion, passive optical cavity. We have achieved direct stabilization
We present results on the ultrafast dynamics of pure hydrogen-bonding solvents, obtained using femtosecond Fourier-transform optical-heterodyne-detected, Raman-induced Kerr effect spectroscopy. Solvent systems we have studied include the formamides, water, ethylene glycol, and acetic acid. Inertial and diffusive motions are clearly resolved. We comment on ...
The dissociation reaction of Mercuric Iodide is examined experimentally using femtosecond transition-state spectroscopy (FTS). The reaction involves symmetric and antisymmetric coordinates and the transition-state is well-defined: IHgI yields (IHgI) Qs'Qa...
in the SPM tip-surface gap by tilting the prism slightly off the ATR minimum angle. Thus, the measured signal to a metal SPM tip. FOS-SPM measurements are shown to obtain femtosecond time resolution in optically induced device technology. The experi- mental measurement of the rate of reaction at individual surface sites
A 250 kHz femtosecond laser was used to induce a one-step precipitation of Ag nanoparticles and the simultaneous element redistribution in Ag ion doped glass. After femtosecond laser exposure, a ring-shape region was formed. Besides, as a result of an optical spherical aberration effect, a nonuniform laser intensity distribution along the incident ...
We used a regeneratively amplified Ti:sapphire femtosecond laser to create optical birefringence in an isotropic glass medium. Between two crossed polarizers, regions modified by the femtosecond laser show bright transmission with respect to the dark background of the isotropic glass. This observation immediately suggests that these regions possess optical ...
The quantum control of the ionization of potassium atoms using shaped intense femtosecond laser pulses is investigated. We use sinusoidal phase modulation as a prototype for complex shaped pulses to investigate the physical mechanism of the strong-field quantum control by shaped femtosecond light fields. The influence of all parameters characterizing the ...
A novel broadband femtosecond version of the stimulated emission pumping (SEP) technique is demonstrated. A nonstationary ground state of a molecular sample in the condensed phase is prepared by two optical pulses. The first picosecond PUMP pulse resonantly excites the sample. The second femtosecond DUMP pulse, which is tuned to the molecular fluorescence ...
Study of physical and chemical events accompanying light-matter interaction in pico- and femtosecond time scale have become possible with the use of ultrashort laser pulses. With the progress in generation of ultrashort laser pulses, the ultrafast optical spectroscopy, as a tool for dynamic study, is still evolving rapidly.
Ultrafast dynamics of ?-carotene encapsulated in single-walled carbon nanotubes (SWCNTs) was investigated by femtosecond absorption spectroscopy. Energy transfer from the excited states of ?-carotene to SWCNTs (light-harvesting function) has been observed.
We show by pump-probe spectroscopy that the optical response of a fishnet metamaterial can be modulated on the femtosecond time scale. The modulation dynamics is dominated by pump-induced changes in the constituting dielectric medium, but the strength of ...
Femtosecond pulses offer several advantages over more conventional nanosecond pulses for laser-induced breakdown spectroscopy applications. These advantages include improved ablation, lower breakdown threshold, more efficient energy deposition, and less t...
, and autocorrelation femtosecond optical spectroscopy show that, after the linkage formation, the particles the wafer at a slow speed. Subsequent immersion in an ultrasound bath of chlorobenzene crumbles the top film
This report includes a book chapter (review article), two of our recent Physical Review B (PRB) articles, and our publication list. In the first PRB article femtosecond pump-probe spectroscopy and time-resolved photoluminescence were used to investigate t...
This report describes research on eight different projects ranging from fundamental quantum optics to optical engineering. Topics discussed include the following: Study of magnetoexciton femtosecond spectroscopy, semiconductor microcavities, and periodic ...
The authors have prepared and characterized photosensitized zinc oxide (ZnO) nanoclusters, dispersed in methanol, using carboxylated coumarin dyes for surface adsorption. Femtosecond time-resolved emission spectroscopy allows the authors to measure the ph...
Fig. 2 depicts the Stokes-side Raman spectrum of Chalcogenide glass. It is clearly shown that the cut AND FUTURE WORK It was demonstrated, to our knowledge the first time, that a Raman spectrum close glasses Fig. 2. Raman spectrum of Chalcogenide glass #12;
... 20. T. Gong, LX Zheng, W. Xiong, W. Kula, R. Sobolewski, JP Zheng, H-. S. Kwok, and JR Gavaler, "Femtosecond Spectroscopy of Y-Ba-Cu-O Thin ...
Recent work on the subject of solvation dynamics has concentrated on understanding the ultrafast dynamics of intermolecular interactions in strongly interacting, polar, and hydrogen-bonding solvents. In general, investigations into the effects of solvatio...
We report on the use of a novel phase element to control the far- field intensity pattern generated by a high-peak-power, femtosecond laser. The pre-determined intensity pattern results in a well defined location of the filaments formed by the propagation...
We study the destructive action of femtosecond pulses (200 fs) on the human cataractous crystalline lens and the transmission of the cataractous lens in the terahertz spectral range of electromagnetic oscillations (0.2-1 THz) in relation to the density of the nucleus of the lens.
We report experiments with subpicosecond UV laser filaments for the remote analysis of samples related to objects of cultural heritage. The classic laser-induced breakdown spectroscopy (LIBS) technique finds new avenues through femtosecond filamentation, and dynamic remote LIBS becomes possible. Advantages such as self-regulated laser intensity deposition ...
Photochromic [Ru(bpy)(2)(OSO)](PF(6)), where bpy is 2,2'-bipyridine and OSO is 2-methylsulfinylbenzoate, was investigated by femtosecond transient absorption spectroscopy. The results show that for both S- and O-bonded isomers, a (3)MLCT state is formed on a femtosecond time scale. Also observed is the formation of multiple ...
This work reports on a feasibility study of proximity ablation using femtosecond pulses. Ultra-short pulses were launched to a bare tapered optical fiber and delivered to the sample. The tip-sample distance was controlled by means of shear-force feedback. Consequently, ablation craters with submicrometer dimensions were obtained. Potential analytical applications for Laser ...
We demonstrate a single-beam, standoff (>10 m) detection and identification of various materials including minute amounts of explosives under ambient light conditions. This is obtained by multiplex coherent anti-Stokes Raman scattering spectroscopy (CARS) using a single femtosecond phase-shaped laser pulse. We exploit the strong nonresonant background ...
The use of four-wave mixing techniques in femtosecond time-resolved spectroscopy has considerable advantages. Due to the many degrees of freedom offered e.g. by coherent anti-Stokes Raman scattering (CARS), the dynamics even of complex systems can be analyzed in detail. Using pulse shaping techniques in combination with a self-learning loop approach, ...
The resonant nonlinear refraction in rare-earth-doped solids is studied with femtosecond degenerate pump-probe two-beam coupling spectroscopy. The phase modulation induced by the pump pulses is shown to result in a significant contribution to the differential change of the probe transmission. An ultrafast resonant nonlinear refractive index of the order of ...
The femtosecond selective spectroscopy of vibrational-rotational dynamics of molecules in a liquid was realized using optical Kerr effect registration under two-pulse nonresonant excitation. The object chosen for the study was the chloroform at room temperature. It was shown that control of the separate molecular motions by creating the constructive or ...
Femtosecond stimulated Raman spectroscopy (FSRS) has proven to be a reliable probe of condensed phase dynamics by simultaneously achieving both exceptional temporal and frequency resolution. We report on preliminary attempts to utilize FSRS as a probe of vibrational relaxation on the ground electronic state of cyclohexane. We implement a 400 nm Raman ...
never been directly measured. We approach this problem using ultrafast X-ray absorption spectroscopy femtosecond transient absorption spectroscopy and the results are summarized in Figure 1c.11,37,38 Here we of the detector. The spectral data are collected from 7017 to 7624 eV in steps of 4 eV. Transient XAS measurements
the resulting protein fractions. For coherent nonlinear optical applications such as EVV 2D-IR spectroscopy/femtosecond nonlinear spectroscopy platform comprising 4 computer- controlled white light seeded optical parametric) CARS signal from BSA deposited on a glass coverslip. (i) Resonant (F, 1005 cm-1 ) and (ii) nonresonant
) intramolecular proton transfer (ESIPT). A detailed analysis of the transient absorption measurements resolved fluorescence up-conversion and transient absorption spectroscopy. The observation of dual-resolved transient absorption spectroscopy and fluorescence up-conversion spectroscopy study of carminic acid
We experimentally demonstrated remote sensing of the constituents of microparticles in air by combining laser-induced breakdown spectroscopy (LIBS) and lidar, using femtosecond terawatt laser pulses. Laser pulses of 70 fs duration and 130 mJ energy generated filaments when focused at a focal length of 20 m and the pulses irradiated artificial saltwater ...
Reaction centers of bacterial photosynthesis are ideal systems to study photosynthetic energy conversion. Femtosecond spectroscopy has delivered extensive information on the molecular mechanisms of the primary electron transfer. The data show, that primary electron transfer is an ultrafast stepwise reaction, where the electron is transferred via closely ...
Transient absorption spectroscopy is a powerful tool for the study of photoreactions on time scales from femtoseconds to seconds. Typically, reactions slower than approximately 1 ns are recorded by the "classical" technique; the reaction is triggered by an excitation flash, and absorption changes accompanying the reaction are recorded in real time using a ...
Transient absorption spectroscopy is a powerful tool for the study of photoreactions on time scales from femtoseconds to seconds. Typically, reactions slower than ~1 ns are recorded by the ``classical'' technique; the reaction is triggered by an excitation flash, and absorption changes accompanying the reaction are recorded in real time using a continuous ...
InN grown on sapphire substrates with GaN or AlN buffer layers exhibits a variety of unique electronic properties for the development of brighter photo-conducting THz-radiation sources. Since InN is a narrow band gap semiconductor it is also an attractive candidate for compact and lightweight THz-spectroscopy and imaging systems based on femtosecond fiber ...
Femtosecond lasers have permitted the development of direct time-domain spectroscopy in the THz or far-infrared spectral region. In this approach, a femtosecond laser pulse is frequency down converted to produce a baseband electromagnetic transient. The electric field waveform can then be detected in an appropriate medium using a time ...
A laser-based tabletop approach to femtosecond time-resolved photoelectron spectroscopy with photons in the vacuum-ultraviolet (VUV) energy range is described. The femtosecond VUV pulses are produced by high-order harmonic generation (HHG) of an amplified femtosecond Ti:sapphire laser system. Two generations of the ...
Extending spatial resolution in laser-based chemical analysis to the nanoscale becomes increasingly important as nanoscience and nanotechnology develop. Implementation of femtosecond laser pulses arises as a basic strategy for increasing resolution since it is associated with spatially localized material damage. In this work we study femtosecond laser far- ...
Thin films of La0.6Ca0.4CoO3 were grown by pulsed laser ablation with nanosecond and femtosecond pulses. The films deposited with femtosecond pulses (248 nm, 500 fs pulse duration) exhibit a higher surface roughness and deficiency in the cobalt content compared to the films deposited with nanosecond pulses (248 nm, 20 ns pulse duration). The origin of ...
The high temporal resolution and broad bandwidth of a femtosecond laser system are exploited in a pair of nonlinear optical studies of surfaces. The dephasing dynamics of resonances associated with the adatom dangling bonds of the Si(111)7 x 7 surface are explored by transient second-harmonic hole burning, a process that can be described as a fourth-order nonlinear optical ...
We theoretically study the spectral phase shift of a midinfrared (MIR) femtosecond pulse generated through parametric frequency down-conversion in dispersive media, with an emphasis on the effect of group-velocity dispersion (GVD), with the aim of obtaining guidelines for dispersion compensation and pulse compression in such systems. It is found that the spectral phase of the ...
PC12 cells, which are derived from a rat pheochromocytoma, were independently patterned utilizing an impulsive force resulting in impulsive shockwave and cavitation bubble generation by focused femtosecond laser irradiation. Since the PC12 cells respond reversibly to nerve growth factor by induction of the neuronal phenotype, we can assess an influence that the impulsive force ...
Femtosecond laser pulses have been widely used as a tool to study molecular ionization and fragmentation. This article bridges the application of femtosecond laser technology in early research focused on small isolated molecules with that in modern biological mass spectrometry for proteomics and metabolomic analysis on large (140+ atoms) biomolecules. The ...
We report on the welding of fused silica with ultrashort laser pulses at high repetition rates. Femtosecond laser pulses were focused at the interface of two optically contacted fused silica samples. Due to the nonlinear absorption in the focal volume and heat accumulation of successive pulses, the laser acts as a localized heat source at the focus ...
Nanocrystalline silicon gratings were fabricated by applying both femtosecond-laser-interference crystallization and post thermal annealing to amorphous silicon (a-Si) nanoclusters embedded within a silicon nitride matrix. Catalytic chemical vapor deposition was used to fabricate the embedded a-Si nanoclusters, and the formation of a-Si nanoclusters was confirmed by ...
The carrier envelope (CE) phase of a femtosecond laser was stabilized. The laser produces an ultra stable comb of frequency spanning the visible region and basically is an optical frequency synthesizer and ready for the frequency domain applications. In this context, the CW stability of the Ti:sapphire laser is discussed to provide a procedure for the ...
The most challenging application of time-resolved spectroscopy is to watch the motion of atoms directly. In the current experiment, we were able to follow the displacement of atoms in silicon after excitation with an intense near infrared femtosecond laser pulse with time-resolved x-ray absorption spectroscopy. The sub-20-fs x-ray ...
In this paper we present a tensor analysis of Raman induced polarization spectroscopy (RIPS), a variation of time-resolved rotational coherence spectroscopy (RCS), developed in our laboratory to study coherent rotational motions in fluids over a range of densities. Based on the irreducible tensor algebra, the analysis separates the fundamental molecular ...
Precision spectroscopy of the simple hydrogen atom has inspired dramatic advances in optical frequency metrology: femtosecond laser optical frequency comb synthesizers have revolutionized the precise measurement of optical frequencies, and they provide a reliable clock mechanism for optical atomic clocks. Precision spectroscopy of the ...
Microstructure fibres with a special dispersion profile are shown to allow the creation of highly efficient sources of frequency-tunable ultrashort pulses with a smooth envelope and a controlled chirp for high-resolution time-resolved coherent anti-Stokes Raman scattering spectroscopy. We present pulse-duration and group-delay measurements for anti-Stokes signals generated in ...
Femtosecond time-resolved photoelectron spectroscopy is emerging as a useful technique for investigating excited state dynamics in isolated polyatomic molecules. The sensitivity of photoelectron spectroscopy to both electronic configurations and vibrational dynamics makes it well suited to the study of ultrafast nonadiabatic processes. ...
Nonlinear spectroscopy using coherent anti-Stokes Raman scattering and femtosecond laser pulses has been successfully developed as powerful tools for chemical analysis and biological imaging. Recent developments show promising possibilities of incorporating CARS into LIDAR system for remote detection of molecular species in airborne particles. The ...
These proceedings represent papers presented at the eighth international symposium on Resonance Ionization Spectroscopy held in State College, Pennsylvania USA. The symposium was sponsored by the U.S. Department of Energy and Office of Health and Environmental Research. The symposium addressed the following subjects: molecular resonance ionization ...
We present a novel setup for the investigation of ultrafast dynamic processes in a liquid jet using time-resolved photoelectron spectroscopy. A magnetic-bottle type spectrometer with a high collection efficiency allows the very sensitive detection of photoelectrons emitted from a 10 ?m thick liquid jet. This translates into good signal/noise ratio and rapid data acquisition ...
Femtosecond laser ablation of gallium arsenide investigated with time- of-flight mass spectroscopy laser-induced ablation of gallium arsenide using time-of-flight mass spectroscopy. At the ablation into a collisional expansion process. Above the ablation threshold, the behavior of gallium particles can
-induced ablation of gallium arsenide and silicon using time-of-flight mass spectroscopy. Below the ablation irradiation of Gallium Arsenide. We estimated maximum surface temperatures of the order of 3500 K laser-heated gallium arsenide" Appl. Phys. A 36, 1, (1986). 7 J.M. Liu "Simple technique
As an alternative to focusing nanosecond pulses for stand-off LIBS detection of energetic materials, we use self-channeled femtosecond pulses from a Ti:Sapphire laser to produce filaments at 12 meters and create a plasma on copper, graphite and polyisobutylene film. We show the possibilities of this Laser-Induced Breakdown Spectroscopy configuration for ...
a singletensorelement of the nonlinear optical response of the medium. Femtosecond off-resonant nonlinear spectroscopies of the nonresonant third-order nonlinear optical susceptibility of simple liquids, carbon tetrachloride and benzene to conventional techniques, such as optical heterodyne detected Raman induced Kerr effect ...
Separation of two negative charges in aqueous PtBr{_6}2- is investigated by means of femtosecond broadband pump-probe spectroscopy using several excitation wavelengths, in concert with time-resolved x-ray absorption spectroscopy and DFT/TDDFT calculations.
High resolution He I(alpha) photoelectron spectroscopy of formaldehyde and ketene and their deuterated compounds, are reported. The combination of a (H2CO) double-pass high-resolution electron-energy analyzer and effective rotational cooling of the sample...
We have studied the spectroscopy, kinetics and non-linear characteristics of conjugated organic dyes by means of a new femtosecond transient spectroscopy system that allows us to study delta A values as small as 0.003. We were able to measure accurately a...
waveforms, has facilitated many advances in spectroscopy, nonlinear fiber optics, and high-field physics the nonresonant background and to noise. � 2004 Optical Society of America OCIS codes: 320.0320.190.0190, 320- linear spectroscopy and microscopy,8 in which pulse shapes that maximize and minimize a resonant coher
We present direct observation of the velocity-selective optical pumping of the Rb ground state hyperfine levels induced by 5S{sub 1/2}{yields}5P{sub 1/2} femtosecond pulse-train excitation. A modified direct frequency comb spectroscopy based on the fixed frequency comb and a weak cw scanning probe laser was developed. The femtosecond ...
Tin doped indium oxide (ITO) is a n-type highly degenerate, wide band-gap semiconductor that is extensively used for many engineering applications. Pulsed laser ablation of indium tin oxide in the nano and femtosecond regime has been performed in our laboratory. Plume diagnostics has been carried out by means of a fast Intensified Coupled Charge Device (ICCD) camera. Optical ...
We propose to develop a true user facility for ultrafast x-ray science at the Advanced Light Source. This facility will be unique in the world, and will fill a critical need for the growing ultrafast x-ray research community. The development of this facility builds upon the expertise from long-standing research efforts in ultrafast x-ray spectroscopy and the development of ...
Our experiment shows that external focusing strongly influences the plasma density and the diameter of femtosecond Ti-sapphire laser filaments generated in air. The control of plasma filament parameters is suitable for many applications such as remote spectroscopy, laser induced electrical discharge, and femtosecond laser material ...
Forbidden optical transitions in trapped ions are of great interest for high precision spectroscopic applications. We report on work to drive the ^2S1/2(F=0) -- ^2D3/2(F=2) electric quadrupole transition in ^171Yb^+ ions with light derived directly from a femto-second frequency comb. To this end we have trapped and laser-cooled a single ^171Yb^+ ion and minimized its driven ...
The dynamics of excited-state double proton transfer of model DNA base pairs, 7-azaindole dimers, is reported using femtosecond fluorescence spectroscopy. To elucidate the nature of the transfer in the condensed phase, here we examine variation of solvent polarity and viscosity, solute concentration, and isotopic fractionation. The rate of proton transfer ...
This paper studies the photosensitive effect of cerium oxide on the precipitation of Ag nanoparticles after femtosecond laser irradiating into silicate glass and successive annealing. Spectroscopy analysis and diffraction efficiency measurements show that the introduction of cerium oxide may increase the concentration of Ag atoms in the ...
Without cavity dumping or external amplification, we report a femtosecond Cr:forsterite laser with a 1.4 W output power and 2 W in continuous wave (CW) operated with a crystal temperature of 267 K. In the femtosecond regime, the oscillator generates Kerr-lens-mode-locked 84 fs pulses with a repetition rate of 85 MHz, corresponding to a high 16.5 nJ pulse ...
... performed preliminary experiments which demonstrated that hyperpolarized 129Xe spectroscopy may be useful in the diagnosis of atherosclerosis. ...
Femtosecond time-resolved fluorescence spectra technique based on non-collinear optical parametric amplification is a new method for ultrafast spectroscopy research In the present report, the authors discuss the dynamic range for amplifying fluorescence. The supercontinuum seed can be amplified linearly to its transient intensity. Due to large ...
We report on a high peak power femtosecond modelocked VECSEL and its application as a drive laser for an all semiconductor terahertz time domain spectrometer. The VECSEL produced near-transform-limited 335 fs sech2 pulses at a fundamental repetition rate of 1 GHz, a centre wavelength of 999 nm and an average output power of 120 mW. We report on the effect that this high peak ...
We follow the evolution of the spin and orbital angular momentum of a thin Ni film during ultrafast demagnetization, by means of x-ray magnetic circular dichroism. Both components decrease with a 130�40fs time constant upon excitation with a femtosecond laser pulse. Additional x-ray absorption measurements reveal an increase in the spin-orbit interaction by 6�2% during ...
Using a femtosecond laser processing technique, we produce the black platinum with absorptance of about 95% over a broad wavelength range from ultraviolet to infrared. From scanning electron microscopy and energy dispersive x-ray spectroscopy studies, we find that the enhanced absorption of the black metal is due to a variety of nano- and microscale ...
We have measured the ultrafast pure solvent dynamics of highly power liquids, formamide (FA), N-methylformamide (NMF), N-methylacetamide (NMA), N-methylpropioamide (NMP) and N,N{prime}-dimethylformamide (DMF) using femtosecond optical-heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). The effects of deuteration and ...
We focus on IR sensors with lower reflection for the wavelength around 10 ?m, strongly awaited for detecting human bodies. A concave structure was designed as a more suitable reflection-free structure for IR light, and an optical system with a femtosecond laser was employed for verification of the effectiveness of the structure. The microstructures prepared through this ...
We experimentally demonstrate that the use of a weak seed pulse of energy less than 0.4% of the pump results in a spectral energy enhancement that spans over 2 octaves and a total energy enhancement of more than 3 times for supercontinua generated by millijoule level femtosecond pulses in Krypton gas. Strong four-wave mixing of the pump-seed pulse interacting in the gas is ...
In this study we report for the first time a method for direct patterning of silicon oxide on a silicon substrate by irradiation with a femtosecond laser of Mega Hertz pulse frequency under ambient condition. Embossed lines of silicon oxide with around 3 approximately 4 microm width and less than 100 nm height were formed by controlling the parameters such as laser pulse power ...
Ultrafast photoinduced electron transfer (PET) from N,N-dimethylaniline to coumarin dyes in cetyltrimethylammonium bromide (CTAB) micelle is studied using femtosecond upconversion spectroscopy. The rate of PET in a CTAB micelle is found to be highly nonexponential with components much faster ({approx}10 ps) than the slow components of solvation dynamics. ...
Femtosecond laser ablation of titanium has been studied via time-of-flight (TOF) and emission spectroscopy measurement. Laser pulses of 80 fs full width at half maximum at {lambda}=800nm were delivered by a Ti:sapphire femtosecond laser system. A vacuum chamber with a base pressure of 10{sup -7}Torr was built for ion TOF measurement. ...
The mechanism of dc-electric-field-induced second-harmonic (EFISH) generation at weakly nonlinear buried Si(001)-SiO2 interfaces is studied experimentally in planar Si(001)-SiO2-Cr MOS structures by optical second-harmonic generation spectroscopy with a tunable Ti:sapphire femtosecond laser. The spectral dependence of the EFISH contribution near the direct ...
We analyze the advantages of remotely sensing metallic targets using femtosecond laser-induced breakdown spectroscopy by studying the temperature and electron density of the plasma ejected from a lead target produced by femtosecond laser pulse filamentation in ambient air. The electron density of 8x10{sup 17} cm{sup -3} and the plasma ...
We analyze the advantages of remotely sensing metallic targets using femtosecond laser-induced breakdown spectroscopy by studying the temperature and electron density of the plasma ejected from a lead target produced by femtosecond laser pulse filamentation in ambient air. The electron density of 8�1017 cm-3 and the plasma ...
Rectifying properties of semiconductor liquid junctions make them a simple system for converting and storing optical energy. However, interfacial electron or hole carrier transfer and competing non-radiative (energy loss) channels are not well understood at surfaces. This research has explored the use of three optical techniques, Surface Space Charge Electrooptic Sampling, Surface Restricted ...
Femtosecond broadband stimulated Raman spectroscopy (FSRS) is a new technique that produces high-resolution (time-resolved) vibrational spectra from either the ground or excited electronic states of molecules, free from background fluorescence. FSRS uses simultaneously a narrow bandwidth ?1 � 3 ps Raman pump pulse with a continuum ...
Femtosecond broadband stimulated Raman spectroscopy (FSRS) is a new technique that produces high-resolution (time-resolved) vibrational spectra from either the ground or excited electronic states of molecules, free from background fluorescence. FSRS uses simultaneously a narrow bandwidth ~1-3 ps Raman pump pulse with a continuum ~30-50 fs Stokes probe ...
Femtosecond coherent anti-Stokes Raman scattering (CARS) spectroscopy offers several advantages over spontaneous Raman spectroscopy due to the inherently high sensitivity and low average power deposition in the sample. Femtosecond CARS can be implemented in a collinear pump/probe beam configuration for ...
A femtosecond laser-irradiated crystallizing technique is tried to convert amorphous Sb2Te3 film into crystalline film. Sensitive coherent phonon spectroscopy (CPS) is used to monitor the crystallization of amorphous Sb2Te3 film at the original irradiation site. The CPS reveals that the vibration strength of two phonon modes that correspond to the ...
The influence of pulse duration on the laser drilling of metals at repetition rates of up to 1 MHz and average powers of up to 70 W has been experimentally investigated using an ytterbium-doped-fiber chirped-pulse amplification system with pulses from 800 fs to 19 ps. At a few hundred kilohertz particle shielding causes an increase in the number of pulses for breakthrough, depending on the pulse ...
A closed-cycle flow cell system was designed and built for application in ultrafast laser spectroscopy. The system features small cycle volume of down to less than 200 ?l, adjustable beam path length, and compatibility with a large variety of solvents. The construction principle is simple, reliable, and versatile. The thickness and material of the windows can be easily ...
Time-resolved vibrational spectroscopy (TRVS) has many unique features and capabilities for elucidating the structural changes of transient species across the fs to ms time frame. The recently developed 10 KHz, 10W ULTRA laser system represents the very latest technology. ULTRA's performance and capabilities will be described for the time resolved infrared, 2D infrared and ...
These proceedings present papers presented at the Seventh International Symposium on resonance ionization spectroscopy and its applications. The meeting was held in Bernkastel-Kues, Germany. topics for the program include ultrasensitive techniques, femtosecond resonance ionization spectroscopy RIS and biological applications, RIS for ...
These proceedings represent papers presented at the Ninth International Symposium on Resonance Ionization Spectroscopy held in Manchester, United Kingdom, in June 1998. The topics discussed represented advances in resonance ionization spectroscopy technology, particularly laser development. Laser systems, such as femtosecond lasers and ...
The field of quantum coherent control, initially formulated with the goal of modifying and manipulating molecular systems, has had a number of applications in atomic and molecular spectroscopy in recent years. This review demonstrates how carefully designed femtosecond pulses could be used to enhance resolution and improve detection in several areas of ...
A time-resolved study of core-level chemical shifts in a monolayer of aromatic molecules reveals complex photoinduced reaction dynamics. The combination of electron spectroscopy for chemical analysis and ultrashort pulse excitation in the extreme ultraviolet allows performing time-correlated 4d-core-level spectroscopy of iodine atoms that probe the local ...
We investigate femtosecond two-dimensional (2D) vibronic spectroscopy of vibrational wave-packet motion in a diatomic molecule. It is shown that the quantum phase acquired during the time evolution in an anharmonic potential leads to phase changes in the 2D spectrum. This is illustrated for the case of a fractional revival which occurs in the dynamics of a ...
Multiphoton tomography for in vivo high-resolution multidimensional imaging has been used in clinical investigations and small animal studies. The novel femtosecond laser tomographs have been employed to detect cosmetics and pharmaceutical components in situ as well as to study the interaction of drugs with intratissue cells and the extracellular matrix under physiological ...
Silicon hyperdoped with chalcogens via femtosecond-laser irradiation exhibits unique near-unity sub-bandgap absorptance extending into the infrared region. The intense light-matter interactions that occur during femtosecond-laser doping produce pressure waves sufficient to induce phase transformations in silicon, resulting in the formation of metastable ...
We report the real-time measurement of the ultrafast reorientational motion of water molecules at the water-air interface, using femtosecond time- and polarization-resolved vibrational sum-frequency spectroscopy. Vibrational excitation of dangling OH bonds along a specific polarization axis induces a transient anisotropy that decays due to the ...
Ultrafast optical switching from an ionic ( I) to a neutral ( N) state in TTF-CA was observed in femtosecond reflection spectroscopy. Charge transfer excitation in the I phase produces N donor ( D0) acceptor ( A0) strings within 2 ps. These initial N states decay with a lifetime of 300 ps at 4 K, but rather multiply leading to macroscopic I-N conversion ...
Two-photon excited spectroscopies from ex vivo human skin are investigated by using a femtosecond laser and a confocal microscope (Zeiss LSM 510 META). In the dermis, collagen is responsible for second harmonic generation (SHG); elastin, nicotinamide adenine dinucleotide (NADH), melanin and porphyrin are the primary endogenous sources of two-photon excited ...
The characteristic time constants of the relaxation dynamics of core-excited atoms have hitherto been inferred from the linewidths of electronic transitions measured by continuous-wave extreme ultraviolet or X-ray spectroscopy. Here we demonstrate that a laser-based sampling system, consisting of a few-femtosecond visible light pulse and a synchronized ...
Ultrafast femtosecond pump and probe transient electronic absorption spectroscopy experiments were performed to gain insights into the photoisomerization dynamics in the condensed phase of two prototypical molecules, stilbene and a derivative of azobenzene. For example, in the stilbene case, a UV pump - continuum probe experiment measures the excited state ...
This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects ...
Herein we present results on the femtosecond laser direct writing and optical characterization studies of two dimensional gratings in fused silica, GE 124, and Foturan� glasses. Varieties of structures were achieved with varying input energy and spatial orientation of the samples. Various characterization techniques including fluorescence spectroscopy, ...
We present some of our results on the femtosecond laser direct writing and characterization of micro-structures in silicate, FoturanTM, and tellurite glasses. Structures with different sizes were fabricated with varying input energy and spatially modified pulse using a slit. Various characterization techniques including fluorescence spectroscopy, micro- ...
We study the temperature evolution of aluminum nanoparticles generated by femtosecond laser ablation with spatiotemporally resolved x-ray-absorption fine-structure spectroscopy. We successfully identify the nanoparticles based on the L-edge absorption fine structure of the ablation plume in combination with the dependence of the edge structure on the ...
