bluuebunny/crossref_metadata_2025 huggingface dataset:
Hyphenated high performance liquid chromatography-thermal lens spectrometry technique as a tool for investigations of xanthophyll cycle pigments in different taxonomic groups of marine phytoplankton
Authors: Logar Jasmina Kožar , Malej Alenka , Franko Mladen
Published: January 2003

Hyphenated high performance liquid chromatography-thermal lens spectrometry (HPLC-TLS) was applied to the determination of carotenoids in four phytoplankton species. Satisfactory separation of diadinoxanthin, diatoxanthin, and other carotenoids was achieved by isocratic HPLC elution providing 40–80 times lower LOD, compared to UV-Vis detector. Besides the interconversion of diadinoxanthin to diatoxanthin, changes of other minor carotenoids under different light conditions were possible to follow. The isocratic HPLC-TLS provides sufficient sensitivity and selectivity for studies of photochemical processes in marine phytoplankton involving pigments, which occur in traces.
Evidence for viscosity, thermal conduction and diffusion waves in the Earth’s atmosphere (invited)
Authors: Hocking W. K.
Published: January 2003

Over the last 40 years, radar studies of atmospheric backscatter have shown tantalizing evidence for flat, mirror-like partial reflectors embedded in the air. These have been observed at all heights, but especially in the stratosphere (above ∼10 km) and mesosphere (especially in the region 60–90 km altitude), and at a variety of frequencies, from 2 to at least 50 MHz. These structures appear to have vertical depths of only a few meters or less. They often seem independent of atmospheric turbulence scatter. Various explanations have been advanced to account for these unusual structures, but a strong candidate is the possibility that they are due to diffusion waves generated by reflection and/or critical level interactions of gravity waves or infrasound. In this review, we will examine the evidence for these structures, and expand on the possibility that they are indeed organized structures which develop due to the diffusive characteristics of the medium.
Development of photothermal near-field scanning optical microscope photothermal near-field scanning optical microscope
Authors: Fujinami Masanori , Toya Kiminori , Sawada Tsuguo
Published: January 2003

Photothermal near-field scanning optical microscope (PT-NSOM) which gives lateral resolution below the diffraction limit has been developed. The substances are excited by the evanescent wave emitted from the small aperture (around 100 nm φ) of the metal-coated optical fiber probe, resulting in a formation of refractive index change, or the so-called thermal lens. The probe laser light introduced coaxially with the excited one is deflected by it and the intensity at the center of the transmitted component of the probe light is measured by a photodiode. The NSOM image based on photothermal phenomena of Au colloids with diameter of 250 nm has been taken and the lateral resolution is estimated to be less than 150 nm.
Photothermal processes on a fast time scale: A small molecule and a biological protein (invited)
Authors: Miyata Ryoji , Terazima Masahide
Published: January 2003

The thermalization rate after the relaxation of a photoexcited ionic molecule [malachite green (MG)] and of a biological protein [deoxymyoglobin (Mb)] were measured by using the acoustic peak delay method of the transient grating technique. It is found that the rate significantly depends on the concentration of MG; the peak delay time decreases with increasing the concentration. This unexpected concentration dependence is explained in terms of the ionic interaction between MG and the counterions. After photoexcitation of Mb, a negative peak delay was observed and interpreted in terms of an interference between the acoustic waves created by a transient thermal expansion of the protein part and by the normal thermal expansion of the medium.
Acoustic investigations of the interface between a metal and an organic compound
Authors: Bonello Bernard , Louis Gérard , Battioni Pierrette
Published: January 2003

Using the picosecond acoustic technique, we have studied how the morphology of the organic molecule affects the thickness of the interfacial layer in organic/aluminum heterostructures. We compare the photoelastic responses of two phthalocyanine and two porphyrine derivatives. Each molecule is constituted of a rigid macrocycle, which is identical for all molecules in a given family, surrounded by hydrocarbon chains having different lengths. For both phthalocyanine and porphyrine derivatives, longer side chains lead to slightly thinner interfaces. The data analysis requires prior knowledge of the sound velocity in the organic layer; we show how we measured this physical parameter in organic layers the thickness of which is in the submicrometer range.
Theoretical treatment for photothermal depth profile of subsurface defects in opaque solids
Authors: Hemida A. A. , Abdalla S. , Hassan A. F. , Negm S. , Talaat H.
Published: January 2003

The deflection of a probe laser beam incident parallel to the surface of an irradiated target with a cylindrical hole inside it showed two maxima at the boundary of the hole. Theoretical treatment employing the integral Laplace transform technique to explain this behavior was developed using a superposition of temperature distributions arising from a real source inside the target and a virtual source above the target.
Optical properties of TiO2 thin films estimated by photothermal deflection spectroscopy
Authors: Ogawa S. , Mori K. , Natsuhara H. , Ohashi T. , Sakakiyama R. , Itoh T. , Yoshida N. , Nonomura S. , Fukawa M. , Sato K.
Published: January 2003

The optical properties of Nb doped TiO2 thin films have been investigated by using the photothermal deflection spectroscopy. The below-gap absorption of amorphous and microcrystalline TiO2 thin films is observed. The absorption coefficient in the below-gap region in microcrystalline TiO2 film decreased with thermal annealing at ∼650 °C. The origin of the below-gap absorption is discussed on the basis of the structural information.
Thermal-lens study of thermo-optical and spectroscopic properties of polyaniline
Authors: Pilla V. , Balogh D. T. , Faria R. M. , Catunda T.
Published: January 2003

Thermal-lens measurements were performed in PVA/PAni solution in function of PAni concentrations which varied from 0.008 to 0.03 (wt %). We observed a very small increase of the thermal diffusivity with PAni concentration from 1.05 to 1.1×10−3 cm2/s. The fluorescence quantum efficiency behavior from the TL results shows that η decreases from 0.48 to 0.09 with the increase of PAni. These results are in agreement with the behavior of fluorescence spectra that decrease with concentration increase. The experiments were carried out with the protonation (doping) state of the polyaniline contained in the solution corresponding to the conducting emeraldine salt.
Exposure time dependence of the photoacoustic and photoluminescence intensities of porous silicon with different wavelengths of excitation light
Authors: Toyoda Taro , Yamazaki Takahiro , Shen Qing
Published: January 2003

We report the exposure time dependence of the photoacoustic (PA) intensities of porous silicon (PS) with different excitation wavelengths together with that of the photoluminescence (PL). Although the PA intensity decreases somewhat slowly with exposure time, the PL intensity undergoes significant degradation at a first stage until 50 min. The exposure time dependencies of PA and PL show the combinations of two exponential decays. Fast decay time in the PA intensity decreases with the increase of the excitation wavelength. On the other hand, that in the PL intensity increases with the increase of the excitation wavelength. In the shorter wavelength excitation, the degradation at first stage in PL is faster than that in PA. However, in the larger wavelength excitation, the degradation at first stage in PL is slower than that in PA. Slow decay times in PA and PL increase with the increase of the excitation wavelength. These experimental results suggest that the change of the optical absorption center is different from that of luminescent center. The former is related to the formation of oxides inside PS layers although the latter relates to the surface of PS.
Resonant photothermal bending spectroscopy at variable temperature 25–150 °C and its application to hydrogenated microcrystalline silicon films
Authors: Kunii T. , Mori K. , Kiriyama T. , Kitao J. , Yoshida N. , Nonomura S.
Published: January 2003

Resonant photothermal bending spectroscopy (RPBS) at various measurement temperatures has been developed for estimating absorption coefficient (α) spectra of thin film semiconductors. The experimentally obtained sensitivity of RPBS was about ten times larger than nonresonant PBS. In vacuum, this technique has been applied to estimate the α spectrum of hydrogenated microcrystalline silicon (μc-Si:H) films at the measurement temperatures from 25 to 150 °C. It is demonstrated that the temperature coefficient of an indirect optical absorption at 1.2–1.8 eV caused by Si microcrystallite is almost the same as that of single crystalline silicon, and the temperature coefficient of below-gap absorption intensity is negative. The reason for the negative temperature coefficient and the energy level of the localized state resulting in the below gap absorption are discussed.
Measuring and predicting the thermoreflectance sensitivity as a function of wavelength on encapsulated materials
Authors: Tessier G. , Jerosolimski G. , Holé S. , Fournier D. , Filloy C.
Published: January 2003

Thermoreflectance microscopy can deliver thermal images with high spatial resolutions by measuring the variations of the reflection coefficient with temperature. It is therefore a unique tool to measure the temperature mapping of integrated circuits with submicronic features. However, integrated circuits are usually protected by a dielectric encapsulation layer which is transparent to visible light. The optical interference which occurs in these layers strongly modifies the reflectivity and can even forbid thermoreflectance measurements at some wavelengths. For each series of circuits, it is therefore necessary to determine the illumination wavelengths for which thermoreflectance will deliver optimal signals. A sequential wavelength scan can deliver this information but it is time consuming and therefore subject to drifts. We have developed a CCD camera-based thermoreflectance microscope coupled to a grating which disperses white light directly onto the CCD. This instrument gives the complete spectra of the reflection coefficient and its temperature dependence, R(λ) and dR/dT(λ), on one or several materials with only one acquisition. The optimal wavelength for thermoreflectance measurements can therefore be measured within minutes on any sample. A model taking into account multiple reflections and the thermal expansion of the encapsulation layer has been developed to explain the spectra R(λ) and dR/dT(λ) measured on encapsulated circuits. It can be used to predict qualitatively the optimal working wavelength.
Dynamics of the plasma and thermal waves in surface-modified semiconductors (invited)
Authors: Salnick Alex , Opsal Jon
Published: January 2003

Quantitative analysis of ion-implanted layers in Si using the damage-based theoretical modeling and experimental results obtained with the photomodulated reflectance (PMR) technique are described. Our theoretical approach [A. Salnick and J. Opsal, J. Appl. Phys. 91, 2874 (2002)] combines calculations of the ion-induced damage depth profiles in semiconductors with the corresponding scaling of the thermal and carrier plasma wave parameters followed by the calculation of the photothermal response from a multilayered sample. Comparison of the simulated theoretical dose dependencies with experimental PMR amplitude and phase data allows us to study the dynamics of the thermal- and carrier-plasma waves in an ion-implanted semiconductor. The regions of the plasma, thermal, and optical component dominance are defined and the photothermal signal behavior is analyzed in the low, intermediate, and high implantation dose ranges. It is shown that the pump and probe beam wavelengths control the nature of the resulting photothermal signal (thermally or plasma dominated) at low doses while self-annealing effects play a significant role in the photothermal signal behavior at high implantation doses.
Characterization of chemical-bath-deposited CdS thin films doped with methylene blue
Authors: Tomás S. A. , Stolik S. , Altúzar V. , Zelaya O. , Lozada R. , Carmona J. J. , Portillo O. , Dávila J. A.
Published: January 2003

The optical and electrical properties of methylene blue-doped CdS films, grown by chemical bath deposition, have been studied. Doping was achieved by adding specific volumes of methylene blue (MB) diluted in distilled water to the chemical bath. X-ray diffraction patterns display the zincblende crystalline structure for all the CdS samples, with a remarked preferred orientation along the (111) direction. The interplanar distance among the (111) planes indicates a minimum value when the relative volume (VR) of MB in the growing solution is about 7%. Photoacoustic absorption spectra show an evolution of the CdS band-gap energy (Eg) when VR increases, indicating adsorption of MB on the CdS microcrystals. Starting from an Eg of 2.42 eV for the undoped sample, an Eg value of nearly 2.49 eV is reached for the sample doped with VR=7% of MB. For higher concentrations, no increase is observed, showing rather a saturation effect. Dark conductivity (σ) measurements at room temperature (RT) display an increase of the conductivity from 1×10−4 Ω−1 cm−1, for the undoped film, up to 3.0×10−2 Ω−1 cm−1 for the highest doping value reached, that is when VR=7%. Thermoelectrical power measurements carried out at RT indicate that the layers are n-type doped, with a density of carriers (n) whose data basically oscillate in the range (5.3±1.3)×1016 cm−3. An exception is found for the sample with VR=7%, for which a value of n=1.02×1017 cm−3 is measured.
Photoacoustic investigation of Cd1−xMnxTe mixed crystals
Authors: Zakrzewski J. , Firszt F. , Łȩgowski S. , Mȩczyńska H. , Marasek A. , Pawlak M.
Published: January 2003

Ternary diluted magnetic semiconductors Cd1−xMnxTe obtained by Bridgman method in the range of composition 0⩽x⩽0.7 were investigated. The photoacoustic spectroscopy with a piezoelectric transducer was employed to evaluate the energy gaps of Cd1−xMnxTe bulk mixed crystals at room temperature. A linear increase of energy gap with increasing x value has been observed. Photoacoustic data were correlated with ellipsometric measurements.
Thermal lens temperature scanning for quantitative measurements in transparent materials (invited)
Authors: Rohling J. H. , Pereira J. R. D. , Medina A. N. , Bento A. C. , Baesso M. L. , Sampaio J. A. , Lima S. M. , Catunda T. , Miranda L. C. M.
Published: January 2003

In this work the ability of thermal lens spectrometry for different temperature studies in transparent materials is discussed. The method was applied in polymers and optical glasses to measure the thermo-optical properties as a function of the temperature. The focus of the discussion will be on the temperature range where the glass transition occurs. The perspectives of future studies in this area will be discussed.
Photoacoustic observation of multiphoton absorption and relaxation parameters in gas mixtures
Authors: Terzić Mira , Markushev Dragan D. , Jovanović-Kurepa Jelena
Published: January 2003

A method is described that allows simultaneous photoacoustic measurements of multiphoton absorption and relaxation parameters in gas mixtures. The “σe” method to determine rotational relaxation parameters was developed. Various approaches for evaluating differential cross sections are discussed.
Study of cross-linking process in grafted polyethylene and ethylene based copolymer using a phase resolved photoacoustic method
Authors: Dias D. T. , Medina A. N. , Baesso M. L. , Bento A. C. , Porto M. F. , Muniz E. C. , Rubira A. F.
Published: January 2003

In this work, the phase resolved photoacoustic method has been employed to monitor water saturated vapor cross linking in both copolymer and grafted polyethylene. The overtone bands and stretching frequencies combinations of the –Si–OH, =CH2, –CH3, and –CH2–CH3 were monitored and analyzed accordingly to a 32 factorial design with nine samples. The results showed that the cross-linking processes were more efficient when the samples were prepared at 80 °C with the catalyst in the concentration range between 3% and 5% for grafted PE, while 70 °C was the best temperature to obtain copolymer.
Photoacoustic study of PET films and fibers dyed in supercritical CO2 reactor
Authors: Olenka L. , Nogueiran E. S. , Medina A. N. , Baesso M. L. , Bento A. C. , Muniz E. C. , Rubira A. F.
Published: January 2003

Photoacoustic (PA) spectroscopy was applied to study the dyeing process in poly(ethylene terephthalate) films and fibers when supercritical (SC) pressure of CO2 is used. The samples were prepared according to a factorial design having four variables in two levels. They were dyed in red or blue. Following the PA intensity as a variable of response, it was applied an algorithm to take into account the effects of the dyeing variable. The results show that treatment and time were the more influent for blue dyed films and fibers. In contrast, time and temperature were more effective for red films. Depth penetration of the red dye shows saturation near 60 μm with a characteristic time of 30 min. Overall, the results presented CO2 pressure as the less effective variable and the SC–CO2 dyeing method being more effective if compared to conventional bath.
Temperature dependence of the thermo-optical properties of water determined by thermal lens spectrometry
Authors: Pedreira P. R. B. , Hirsch L. , Pereira J. R. D. , Medina A. N. , Bento A. C. , Baesso M. L.
Published: January 2003

The high transparency of water makes conventional spectroscopic measurements very difficult to be performed. In this work thermal lens spectrometry is applied to determine the temperature dependence of the thermo-optical properties of distilled and de-ionized water. The experiments were performed in the temperature range between 22 and 70 °C using the mode mismatched thermal lens configuration. The results showed three anomalous regions for the thermo-optical coefficients around 39, 42, and 59 °C. These observations may contribute to a better understanding of the physical and chemical properties of water.
Transient reflecting grating spectroscopy for defect analysis in surface region of semiconductors
Authors: Katayama Kenji , Donen Hiroshi , Sawada Tsuguo
Published: January 2003

Ultrafast transient reflecting grating (TRG) spectroscopy was utilized for defect analysis in the surface region of ion-implanted silicon for the implantation range from 1011 to 1015 cm−2. To deduce signals due to trapped carriers at defect states, the TRG spectra at the delay time of 30 ps were measured because ultrafast carrier dynamics such as many-body recombination had finished before the delay time. According to the dose quantity, the peak of the interband transition was affected and also defect-related transitions emerged. Using this technique, implantation damage can be detected for samples with their dose larger than 1012 cm−2. It was proposed that TRG spectroscopy can be used as a novel analytical method for characterizing defects in the surface region of semiconductors.
Quantitative measurements of sliding friction coefficients of tribological interfaces with a new differential infrared radiometric instrument
Authors: Mandelis Andreas , Li Li , Baddour Natalie , Tennyson Rod C. , Morrison W. Don
Published: January 2003

Experimental sliding friction coefficient (SFC) measurements using a mechanical friction rig and infrared radiometric emission data from a novel instrument monitoring radiant heat generation at the tribological interface of the rig are described. The infrared radiometric (IRM) system features thermal-emission-intensity harmonic modulation with background-radiation-compensating wave forms, leading to differential signal operation mode and suppression of ambient radiation. The mechanical friction rig was used to generate friction between pairs of moving and stationary samples and to provide reference normal-force and friction-force measurements. Correlations between the lock-in amplifier readouts and the SFC data obtained simultaneously from the mechanical system have been established. The ratio of SFCs from adjacent steel surfaces with and without a lubricant film was accurately measured by the IRM instrument.
Nonlinear vibrational spectroscopy of water structures utilizing laser-induced phase transition phenomena in liquid water
Authors: Yui Hiroharu , Sawada Tsuguo
Published: January 2003

Anomalous enhancement of the stimulated Raman scattering (SRS) of water molecules in the OH stretching vibrational region is observed when a laser-induced phase transition from liquid to plasma takes place in liquid water. The SRS is emitted before the phase transition and has a duration of several tens of picoseconds full width at half maximum. From the spectroscopic analysis of the SRS, it is suggested that the excess electrons, which are generated in a few picoseconds before the phase transition, play an important role in the transient SRS enhancement through the change of the nonlinear polarizability induced around the electrons in liquid water. Several applications of the enhanced vibrational spectra in the OH stretching vibrational region to the spectroscopic analyses of local water structures in various environments are also described.
Theory of stress influence on the photoacoustic thermoelastic signal near the vertical crack tips
Authors: Muratikov K. L.
Published: January 2003

The problem of the photoacoustic signal behavior near the vertical crack tips is investigated. It is shown that the dependence of the photoacoustic signal in the linear approximation on residual strains or stresses is similar to that of widely used stress pattern analysis by measurement of thermal emission. The influence of external normal and shear stresses on the photoacoustic signal near the radial crack tips of Vickers indentation is analyzed. It is demonstrated that the photoacoustic method can be used for the determination of the stress intensity factors of cracks related with residual and external stress fields.
Photoacoustic monitoring of changes in the blood circulation
Authors: Pilatou Magdalena C. , Siphanto Ronald I. , van Adrichem Leon N. A. , de Mul Frits F. M.
Published: January 2003

Photoacoustic (PA) signal generation can be used as the basis for a new medical tomographic technique. In this article, we present results, which have been obtained by applying the PA technique on animals and more specifically on Wistar rats. The primary goal was to investigate the possibility of using PA for monitoring the changes in the blood circulation. This was achieved by tracking the vessel position with one-dimensional scans and by monitoring the changes in the signal due to artificially induced changes in the blood circulation.
Determination of parameter β for dual-wavelength pulsed photothermal profiling of human skin
Authors: Majaron Boris , Milner Thomas E. , Nelson J. Stuart
Published: January 2003

In pulsed photothermal profiling of human skin, subsurface blood vessels may be difficult to resolve due to nonselective absorption in the overlying epidermis. The dual-wavelength excitation (DWE) technique solves this problem by exploiting spectral differences between the epidermal melanin and blood hemoglobin. An improved approach to determination of DWE-specific parameter β for depth profiling of port wine stain birthmarks in vivo using the 585 and 600 nm wavelengths is discussed.
Femtosecond pump–probe nondestructive examination of materials (invited)
Authors: Norris Pamela M. , Caffrey Andrew P. , Stevens Robert J. , Klopf J. Michael , McLeskey James T. , Smith Andrew N.
Published: January 2003

Ultrashort-pulsed lasers have been demonstrated as effective tools for the nondestructive examination (NDE) of energy transport properties in thin films. After the instantaneous heating of the surface of a 100 nm metal film, it will take ∼100 ps for the influence of the substrate to affect the surface temperature profile. Therefore, direct measurement of energy transport in a thin film sample requires a technique with picosecond temporal resolution. The pump–probe experimental technique is able to monitor the change in reflectance or transmittance of the sample surface as a function of time on a subpicosecond time scale. Changes in reflectance and transmittance can then be used to determine properties of the film. In the case of metals, the change in reflectance is related to changes in temperature and strain. The transient temperature profile at the surface is then used to determine the rate of coupling between the electron and phonon systems as well as the thermal conductivity of the material. In the case of semiconductors, the change in reflectance and transmittance is related to changes in the local electronic states and temperature. Transient thermotransmission experiments have been used extensively to observe electron-hole recombination phenomena and thermalization of hot electrons. Application of the transient thermoreflectance (TTR) and transient thermotransmittance (TTT) technique to the study of picosecond phenomena in metals and semiconductors will be discussed. The pump–probe experimental setup will be described, along with the details of the experimental apparatus in use at the University of Virginia. The thermal model applicable to ultrashort-pulsed laser heating of metals will be presented along with a discussion of the limitations of this model. Details of the data acquisition and interpretation of the experimental results will be given, including a discussion of the reflectance models used to relate the measured changes in reflectance to calculated changes in temperature. Finally, experimental results will be presented that demonstrate the use of the TTR technique for measuring the electron–phonon coupling factor and the thermal conductivity of thin metallic films. The use of the TTT technique to distinguish between different levels of doping and alloying in thin film samples of hydrogenated amorphous silicon will also be discussed briefly.
Nonlinear surface acoustic wave pulses in solids: Laser excitation, propagation, interactions (invited)
Authors: Kolomenskii Al. A. , Lioubimov V. A. , Jerebtsov S. N. , Schuessler H. A.
Published: January 2003

Laser techniques enabled generation of very high amplitude pulses with acoustic Mach numbers about 0.01. Such waves drive the medium into the nonlinear elastic regime and shock fronts can be formed during their propagation. As an intense surface acoustic wave (SAW) propagates, the temporal evolution of the wave shape provides information on the nonlinear acoustic parameters and the nonlinear elastic constants of the material. The nonlinear propagation of SAW pulses exhibits different types of nonlinear behavior depending on nonlinear acoustic constants. Changes of a SAW pulse shape were calculated using a nonlinear evolution equation. Measurements of SAW pulses in polycrystalline stainless steel have demonstrated that a compression of the pulse takes place in this material corresponding to a positive parameter of the local nonlinearity, which was evaluated by fitting the parameters of the evolution equation to the experimental data. Numerical simulations of a dispersive propagation of nonlinear SAWs in a system comprised of a substrate with a film were performed. A formation of a relatively stable portion of the waveform was found in agreement with recent observations of soliton-like SAW pulses.
Thermal diffusivity measurements in vegetable oils with thermal lens technique
Authors: Bernal-Alvarado J. , Mansanares A. M. , da Silva E. C. , Moreira S. G. C.
Published: January 2003

Using a thermal lensing experimental setup the thermal properties of several vegetable oils were obtained. The samples were oils from Amazonian species and olive (the popular identifications are piqui, copaiba, buriti, and babaçu). The two lasers mismatched mode experimental configuration was used, with a He–Ne laser as the probe and an Ar+ laser as the excitation one. The time resolved spectra were measured using an automatic system, and fitting the aberrant theoretical model to the data, the characteristic relaxation time were obtained, and knowing this value, the thermal property of each oil was solved.
Self-consistent photothermal techniques: Application for measuring thermal diffusivity in vegetable oils
Authors: Balderas-López J. A. , Mandelis Andreas
Published: January 2003

The thermal wave resonator cavity (TWRC) was used to measure the thermal properties of vegetable oils. The thermal diffusivity of six commercial vegetable oils (olive, corn, soybean, canola, peanut, and sunflower) was measured by means of this device. A linear relation between both the amplitude and phase as functions of the cavity length for the TWRC was observed and used for the measurements. Three significant figure precisions were obtained. A clear distinction between extra virgin olive oil and other oils in terms of thermal diffusivity was shown. The high measurement precision of the TWRC highlights the potential of this relatively new technique for assessing the quality of this kind of fluids in terms of their thermophysical properties.
Optothermal in vitro diffusion measurements through silicone membranes
Authors: Cowen J. A. , Liu H. , Xiao P. , Imhof R. E.
Published: January 2003

We report the development of a new method for measuring diffusion rates of surface-applied chemicals through polymer membranes such as polydimethylsiloxane (PDMS). An important feature of the approach is the use of optothermal transient emission radiometry to sense diffusant concentration in a noncontacting, noninvasive way. This allows the method to be adapted to perform similar measurements on human skin in vivo, thus providing a way of cross-verifying in vivo and in vitro measurements. The correlation between in vitro and in vivo diffusion measurements is also important for developing credible alternatives to in vivo testing, for use with toxic chemicals or animal substitution. We present the results of experiments with several polyols diffusing through PDMS membranes of thickness 125 or 250 μm, describing the experimental details, the measurement protocol, the data analysis methods, and a study of measurement errors.
Evolved gas analysis of clay materials
Authors: dos Santos D. R. , Toledo R. , Faria R. T. , Carrió J. G. , da Silva M. G. , Auler L. T. , Vargas H.
Published: January 2003

Ceramic materials were produced at different temperatures, and the gases released during firing were analyzed using a commercial system based on photothermal techniques. Emissions of CO, CO2, NO, N2O, and CH4 were observed, while NH3 and SO2 were not observed within our detection limits (1 ppm). The evolution of crystalline phases, open porosity, volumetric shrinkage, and rupture tension were correlated to the amount of gases released at different temperatures, ranging from 300 to 1200 °C, and these results can be applied to an optimization of the production process.
Exploring liquid–liquid interfaces with transient evanescent grating techniques
Authors: Brodard Pierre , Vauthey Eric
Published: January 2003

A transient grating setup with evanescent wave probing has been developed to investigate ultrafast processes at liquid–liquid interfaces. In order to evaluate the selectivity of this method to the interface, the speed of sound in the low refractive index medium has been measured as a function of the penetration depth of the probe pulse. Our preliminary results indicate an increase of the speed of sound in methanol with decreasing the probe depth from 100 to 70 nm. However, no correlation was found in acetonitrile in the same range. Modifications of the experiment for improving the selectivity to the interface are proposed.
Pulse shaping in infrared thermography for nondestructive evaluation
Authors: Ziadi A. , Galmiche F. , Maldague X.
Published: January 2003

Infrared thermography is a common technique for nondestructive evaluation. In active infrared thermography privileged here, a thermal stimulation is required to generate relevant thermal contrasts on specimens. Among stimulation techniques, pulse heating is one of the most common along with lock-in thermography. In this article, a technique is discussed that shows that by modifying the pulse heating shape, higher thermal contrasts are generated (for a given level of energy injection). In fact, it was found that ideally, it is better to use two pulses separated by a short Δ time interval. Variation of Δ directly influences the thermal contrast. By increasing Δ, the thermal contrast first improves up to a certain level before to reduce below the reference value (single pulse case). This was tested on several materials of low, medium, and high thermal conductivity. Moreover, this was also confirmed by an appropriate thermal model (not discussed in the article). In the text, a theory and experiments are provided.
Numerical study on the nonlinear effects of heat diffusion in composites and its potential in nondestructive testing
Authors: Kalogiannakis Georgios , Van Hemelrijck Danny
Published: January 2003

This study is focused on the nonlinear phenomena during heat diffusion inside composite materials, when considering that thermal properties are variable with respect to temperature. Based on an experimental work, which determined the aforementioned dependencies, a numerical model was developed to simulate the temperature distribution of the one-dimensional transient problem using a sinusoidal thermal excitation. A comparison with the linear case shows that, depending on the loading parameters, heat diffusion has a tendency toward lower temperatures. A signal spectral analysis shows that the characteristics of the fundamental frequency component are different than in the linear case and, in addition, a second harmonic appears. The detection of this harmonic seems to have great potential for photothermal methods.
Common-mode-rejection demodulation lock-in technique for high-resolution characterization of ion implantation in silicon wafers
Authors: Rábago Felipe , Mandelis Andreas
Published: January 2003

In this article, we present the use of frequency-scan and lock-in common-mode-rejection demodulation (CMRD) laser photothermal radiometry to the study of B+, P+, and As+, ion implanted silicon wafers, with and without surface-grown oxides. The implantation energy of the wafers was 100 keV in all the wafers and doses ranged between 1×1011–1×1013 ions/cm2. The CMRD technique is a new demodulation method that was tested after a theoretical study and its implementation in hardened Zr–2.5Nb samples. This technique is applied to silicon ion-implantation monitoring and we report a superior signal resolution in dose range where the conventional frequency scans essentially overlapped: B+ implants in the dose range 1×1012–1×1013 ions/cm2, and P+ implants in the 1×1011–1013 ions/cm2 range. In all other cases where conventional frequency scans could resolve implantation doses, CMRD did not present any significant resolution advantages. It was further established that the pulse separation increment δΔ is the critical CMRD wave form parameter, which controls dose resolution through substantial signal background and noise suppression. The dose resolution improvements afforded by the CMRD technique may be important toward better control of the ion-implantation process in electronic devices, in a dose range which has traditionally been difficult to monitor optically owing to the effects introduced by the early stages of the amorphization process in the implanted layer.
Quantitative analysis of corroded copper patina by step scan and rapid scan photoacoustic Fourier transform infrared spectroscopy
Authors: Faubel Werner , Heissler Stefan , Palmer Richard A.
Published: January 2003

Atmospheric corrosion enhanced by increasing air pollution causes increasing damage at valuable metallic monuments worthy of protection, e.g., the roof of the Stockholm City Hall. To explore the potential use of Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) in quantitative corrosion product analysis, the determination of the chemical composition of copper patina samples formed under atmospheric conditions was studied. As an experimental technique, we used a FTIR spectrometer in combination with sample-gas-microphone PAS using helium as the transfer gas at room temperature. The main components of the different samples—brochantite Cu4SO4(OH)6 and antlerite Cu3SO4(OH)4—were identified by their characteristic vibrational absorption bands. A quantitative analysis of these two components has been performed with rapid- and step-scan FTIR/PAS by using artificially corroded copper samples with differing ratios of composition. From these data, calibration curves were obtained allowing a nondestructive determination of the brochantite/antlerite ratio for quality control within an accuracy of about 10%.
Investigation of adsorption by thermal lensing
Authors: Proskurnin M. A. , Kononets M. Yu. , Bendrysheva S. N. , Proskurnina E. V. , Nedosekin D. A. , Khrycheva A. D.
Published: January 2003

Thermal lensing was used for the characterization of adsorption on laboratory glassware at a nanogram concentration level in solution. Sorption kinetics was studied, the sorption capacity of the glass for test substances was characterized, which was found to be several ng cm−2. Factors affecting adsorption were discussed. A procedure for handling laboratory glassware for eliminating sorption effects in determining nanogram amounts of iron in aqueous solutions was developed.
Characterization of pyroelectric detectors between 170 and 300 K using the photopyroelectric technique
Authors: Bentefour E. H. , Glorieux C. , Chirtoc M. , Thoen J.
Published: January 2003

In this article, we perform a full characterization of the thermal properties of photopyroelectric detectors in a wide temperature range. Within the experimental uncertainties, the results on lithium tantalate are consistent with results from literature. The thermal properties of polyvinilydene fluoride have a complex behavior.
Use of thermal lens spectroscopy to measure the thermal diffusivity, during the gelation process, of sol–gel materials added with Mn
Authors: Martı́nez-Flores J. O. , Limón J. M. Yáñez , Espinoza-Beltran F. J. , Gonzalez-Hernandez J.
Published: January 2003

In this article, we have studied the evolution of the thermal diffusivity of SiO2-based sol–gel material containing various amounts of Mn. The thermal diffusivity was obtained using thermal lens spectroscopy. The thermal diffusivity measured as a function of time, from the precursor liquid solution to the solid glass, shows a behavior with three distinct regimes. These regimes correspond to the different stages of glass formation, the hydrolysis, gelation, and solidification stages. The materials show an optical memory effect, which is produced by the irradiation with a focused laser beam. The laser beam produces a gradient in the refractive index, which can be permanently stored in the material. This local change in the optical properties of the material can be read with a probe laser due to the strong diffraction pattern observed in the transmitted light.
Study on the femtosecond laser-induced refractive index change in a silicate glass by transient lens method
Authors: Sakakura Masaaki , Terazima Masahide
Published: January 2003

When a laser pulse is tightly focused inside a transparent solid material, a permanent structural change occurs in the focused region. This phenomena will be very useful to construct many important devices such as integrated optical waveguides, or three-dimensional photonic devices. The mechanism of the light induced structural change inside a glass was investigated in a picosecond–nanosecond region by a transient lens technique with an intense subpicosecond pulsed laser and microscope objective lens. Just after the irradiation of the pump pulse inside the glass, a concave lens was instantaneously created. After this fast response signal, an oscillation with some different frequencies in GHz region was observed. The origin of the oscillation is discussed.
Photoacoustic effect in semiconductors: Influence of field temperature on carrier diffusion and recombination
Authors: Villegas-Lelovsky L. , González de la Cruz G. , Gurevich Yu. G. , Volovichev I. N.
Published: January 2003

A quantitative derivation is presented for the heat transport in bipolar semiconductors taking into account the generation and heating of carriers on the surface of the sample due to an incident modulated laser beam, finite carrier diffusion, and recombination in the solid. The temperature distribution is calculated using appropriate boundary conditions according to the photoacoustic experimental conditions. In addition, special emphasis is made on the heat power density generated in the sample due to the recombination of the electron–hole pair and the effect of the inhomogeneous temperature distribution on the thermal generation rate of carriers in the photoacoustic signal. Finally, the effect of two temperatures associated with the quasiparticle (electrons and phonons) systems is considered in the finite electron–phonon energy interaction in the solid.
Effect of heat treatment on ethylene and CO2 emissions rates during papaya (Carica papaya L.) fruit ripening
Authors: da Silva M. G. , Santos E. O. , Sthel M. S. , Cardoso S. L. , Cavalli A. , Monteiro A. R. , de Oliveira J. G. , Pereira M. G. , Vargas H.
Published: January 2003

Ripening studies of nontreated and treated papaya (papaya L) are accomplished by monitoring the ethylene and CO2 emission rates of that climacteric fruit, to evaluate its shelf life. The treatments simulate the commercial Phitosanitarian process used to avoid the fly infestation. Ethylene emission was measured using a commercial CO2 laser driven photoacoustic setup and CO2, using a commercial gas analysis also based on the photothermal effect. The results show a marked change in ethylene and CO2 emission rate pattern for treated fruits when compared to the ones obtained for nontreated fruits and a displacement of the climacteric pick shown that the treatment causes a decrease of shelf life of fruit.
Photorespiration and temperature dependence of oxygen evolution in tomato plants monitored by open photoacoustic cell technique
Authors: Vargas-Luna M. , Madueño L. , Gutiérrez-Juárez G. , Bernal-Alvarado J. , Sosa M. , González-Solı́s J. L. , Sánchez-Rocha S. , Olalde-Portugal V. , Alvarado-Gil J. J. , Campos P.
Published: January 2003

The open photoacoustic cell was used to monitor the evolution rate of oxygen from tomato leaves. Estimates of the relative amount of released oxygen in vivo and in situ conditions as influenced by ambient temperature are being presented. Photorespiration phenomenon is shown to dominate above a critical temperature. The evolution of this critical point is analyzed as a function of the environmental temperature.
Ricinus communis-based biopolymer and epidermal growth factor regulations on bone defect repair: A rat tibia model
Authors: Mendoza-Barrera C. , Meléndez-Lira M. , Altuzar V. , Tomás S. A.
Published: January 2003

We report the effect of the addition of an epidermal growth factor to a Ricinus communis-based biopolymer in the healing of a rat tibia model. Bone repair and osteointegration after a period of three weeks were evaluated employing photoacoustic spectroscopy and x-ray diffraction. A parallel study was performed at 1, 2, 3, 4, 5, 6, 7, and 8 weeks with energy dispersive x-ray spectroscopy. We conclude that the use of an epidermal growth factor (group EGF) in vivo accelerates the process of bony repair in comparison with other groups, and that the employment of the Ricinus communis-based biopolymer as a bone substitute decreases bone production.
Scanning thermal microwave resonance microscopy of Ni nanodots
Authors: Meckenstock R. , Spoddig D. , Dietzel D. , Pelzl J. , Bucher J. P.
Published: January 2003

Ni nanodots of random shape were deposited electrolytically on a mica substrate covered by Au with [111] texture. The dots had a maximum size of 260 nm in height and 150 nm in diameter. These dots were investigated by conventional and locally resolved ferromagnetic resonance (FMR). We present for the first time FMR spectra taken from a single nanodot by detection of the thermoelastic response of the microwave absorption in the dot by a scanning tunneling microscope (STM). The single Ni dots show sharp separate resonance lines, governed by the influence of shape anisotropy. We could prove that the expansion of the sample detected by the z-piezo voltage of the STM signal in the FMR line is due to the thermoelastic effect caused by heating through the absorbed microwave power.
Frequency dependence of the thermosonic effect
Authors: Han Xiaoyan
Published: January 2003

The thermosonic nondestructive evaluation technique employs an infrared (IR) camera to image defects which are excited via ultrasonic waves. The dissipation of ultrasonic energy at the faces of the defect causes an increase in temperature in the vicinity of the defect, which is imaged by the IR camera. The defect is seen as a bright IR source within a dark background field. It has been learned that the coupling of high-power sound into a solid object is highly nonlinear. However, it is never clear whether it is the fundamental frequency or some harmonic that is most effective in heating the crack. Results of the study frequency dependence of the thermosonic effect with both 20 and 40 kHz are presented in this article, along with vibrational information in the vicinity of a crack.
Theoretical calculation of the dispersion relation for polymeric thin films: Determination of the thermal diffusivity using photothermal microscopy
Authors: de Freitas L. R. , Mansanares A. M. , da Silva E. C.
Published: January 2003

Photothermal reflectance microscopy can be used to characterize thin films grown on substrates in two different ways: (a) scanning modulation frequency with both the pump and probe beams coincident and (b) varying the pump–probe beam distance for several modulation frequencies. In the second case, the phase lag behavior, as a function of the beam separation, gives the effective wave number of the thermal wave along the surface. A plot of the wave number versus frequency provides a dispersion relation. Such a relation can be obtained by modeling the thermal problem of the system, and from the experimental data analysis one can determine the thermal parameters of the film and substrate. In the case of films with high thermal diffusivities, it is possible to find an analytical expression for the dispersion relation [A. A. Maznev et al., J. Appl. Phys. 78, 5266 (1995)]. However, in the case of films with low thermal diffusivities numerical calculation is needed. In this article we present the results of such a calculation for polymer films which have low diffusivities compared to the substrates (glass and silicon). The films were assumed to be opaque to both the pump and probe beams, i.e., both absorption and reflection occur at the film surface. It was observed that at high modulation frequencies the dispersion relation splits into two branches, one characteristic of the film, which is valid for small distances between the pump and probe, and the other characteristic of the substrate, valid for large distances.