Pub Date : 2002-03-01DOI: 10.1080/13642810208223129
V. Crupi, D. Majolino, P. Migliardo, V. Venuti
Abstract We studied, versus temperature, the vibrational properties of ethylene glycol (EG) (H—(O—CH2—CH2)—OH) and ethylene glycol monomethyl ether (EGmE) (CH3—(O—CH2—CH2)—OH), in solution with poly(ethylene oxide) (PEO) (H—(O—CH2—CH2)n—OH) at different concentrations, by Fourier transform infrared spectroscopy. These homologous systems differ for the number of OH end groups, in particular two for EG, and one for EGmE. Connecting the O—H stretching band shape to the different hydrogen bond imposed local environments, we clarified the role of this bond in the solute-solvent interactions, obtaining information on the quality of these solvents.
{"title":"Influence of hydroxyl end groups on the vibrational properties of polymer and monomer solutions: An attenuated total reflectance Fourier transform infrared absorbance study","authors":"V. Crupi, D. Majolino, P. Migliardo, V. Venuti","doi":"10.1080/13642810208223129","DOIUrl":"https://doi.org/10.1080/13642810208223129","url":null,"abstract":"Abstract We studied, versus temperature, the vibrational properties of ethylene glycol (EG) (H—(O—CH2—CH2)—OH) and ethylene glycol monomethyl ether (EGmE) (CH3—(O—CH2—CH2)—OH), in solution with poly(ethylene oxide) (PEO) (H—(O—CH2—CH2)n—OH) at different concentrations, by Fourier transform infrared spectroscopy. These homologous systems differ for the number of OH end groups, in particular two for EG, and one for EGmE. Connecting the O—H stretching band shape to the different hydrogen bond imposed local environments, we clarified the role of this bond in the solute-solvent interactions, obtaining information on the quality of these solvents.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80897004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223139
F. Venturini, P. Gallo, M. Ricci, A. Bizzarri, S. Cannistraro
Abstract An inelastic neutron scattering experiment on water confined in Vycor glass has been performed to test the behaviour of the hydrogen dynamics against the predictions of the mode coupling theory, in the β-relaxation region.
{"title":"Study of the β relaxation in supercooled confined water","authors":"F. Venturini, P. Gallo, M. Ricci, A. Bizzarri, S. Cannistraro","doi":"10.1080/13642810208223139","DOIUrl":"https://doi.org/10.1080/13642810208223139","url":null,"abstract":"Abstract An inelastic neutron scattering experiment on water confined in Vycor glass has been performed to test the behaviour of the hydrogen dynamics against the predictions of the mode coupling theory, in the β-relaxation region.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80330182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223145
P. Ossi, A. Miotello
Abstract Diamond-like carbon films have been prepared by KrF excimer pulsed-laser deposition at a wavelength of 248 nm, with power densities ranging from 0.05 to 1.85 GW cm−2, in vacuum and in a nitrogen atmosphere. Structural analysis was performed first by Fourier transform infrared spectroscopy, which shows that the films are hydrogen free and become transparent above a threshold power density. The band features indicate that the structure of the films is disordered. Combined visible and ultraviolet (UV) Raman spectroscopies allowed us to enhance the scattering cross-section from sp3-coordinated carbon with respect to the sp2 signals. In visible Raman spectra the D and G peaks are found; in UV Raman spectra, besides the blue-shifted G peak and the T peak, a further peak, not reported before, at about 1400 cm−2 is evident in spectra from films deposited in vacuum at low fluences. An analysis of the evolution of Raman fitting parameters with increasing deposition power density shows that above a threshold value of about 0.5 GW cm−2 a structural transition occurs in the films deposited in vacuum from mainly disordered graphitic to predominantly amorphous tetrahedrally bonded carbon. The presence of nitrogen during deposition results in relevant modifications of the Raman spectra, associated with changes in the expansion dynamics of the carbon plasma plume.
{"title":"On the structure of thin amorphous carbon films","authors":"P. Ossi, A. Miotello","doi":"10.1080/13642810208223145","DOIUrl":"https://doi.org/10.1080/13642810208223145","url":null,"abstract":"Abstract Diamond-like carbon films have been prepared by KrF excimer pulsed-laser deposition at a wavelength of 248 nm, with power densities ranging from 0.05 to 1.85 GW cm−2, in vacuum and in a nitrogen atmosphere. Structural analysis was performed first by Fourier transform infrared spectroscopy, which shows that the films are hydrogen free and become transparent above a threshold power density. The band features indicate that the structure of the films is disordered. Combined visible and ultraviolet (UV) Raman spectroscopies allowed us to enhance the scattering cross-section from sp3-coordinated carbon with respect to the sp2 signals. In visible Raman spectra the D and G peaks are found; in UV Raman spectra, besides the blue-shifted G peak and the T peak, a further peak, not reported before, at about 1400 cm−2 is evident in spectra from films deposited in vacuum at low fluences. An analysis of the evolution of Raman fitting parameters with increasing deposition power density shows that above a threshold value of about 0.5 GW cm−2 a structural transition occurs in the films deposited in vacuum from mainly disordered graphitic to predominantly amorphous tetrahedrally bonded carbon. The presence of nitrogen during deposition results in relevant modifications of the Raman spectra, associated with changes in the expansion dynamics of the carbon plasma plume.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75616352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223138
J. Swenson, R. Bergman, D. Bowron, S. Longeville
Abstract We have investigated the structure and dynamics of confined water in a fully hydrated sodium vermiculite clay by neutron diffraction and neutron spin-echo (NSE) spectroscopy. All measurements were performed with the Q vector parallel to the clay layers. In the case of the diffraction experiments we used both protonated and deuterated water in order to elucidate the interlayer water structure. The structural results support a picture where the intercalated water is generally ‘liquid like’ with only a small degree of orientational ordering of the water molecules relative to the clay surfaces and other water molecules. The intermediate scattering function S(Q, t) measured by NSE can be described by the Kohlrausch-Williams-Watts stretched-exponential function, probably associated with a broad distribution of relaxation times owing to widely different local environments for the water molecules. Some water molecules are strongly interacting with the clay surfaces or the intercalated Na+ ions, whereas the remaining molecules are interacting only with other water molecules. The Q dependence of the average relaxation time is in good agreement with the Gaussian jump-length distribution model for translational diffusion, suggesting that most of the motions on the experimental time scale (3-3000 ps) have a translational character.
{"title":"Water structure and dynamics in a fully hydrated sodium vermiculite clay","authors":"J. Swenson, R. Bergman, D. Bowron, S. Longeville","doi":"10.1080/13642810208223138","DOIUrl":"https://doi.org/10.1080/13642810208223138","url":null,"abstract":"Abstract We have investigated the structure and dynamics of confined water in a fully hydrated sodium vermiculite clay by neutron diffraction and neutron spin-echo (NSE) spectroscopy. All measurements were performed with the Q vector parallel to the clay layers. In the case of the diffraction experiments we used both protonated and deuterated water in order to elucidate the interlayer water structure. The structural results support a picture where the intercalated water is generally ‘liquid like’ with only a small degree of orientational ordering of the water molecules relative to the clay surfaces and other water molecules. The intermediate scattering function S(Q, t) measured by NSE can be described by the Kohlrausch-Williams-Watts stretched-exponential function, probably associated with a broad distribution of relaxation times owing to widely different local environments for the water molecules. Some water molecules are strongly interacting with the clay surfaces or the intercalated Na+ ions, whereas the remaining molecules are interacting only with other water molecules. The Q dependence of the average relaxation time is in good agreement with the Gaussian jump-length distribution model for translational diffusion, suggesting that most of the motions on the experimental time scale (3-3000 ps) have a translational character.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88359244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223132
P. G. Gabrielli
Abstract The technological relevance of structural glasses has led to increased efforts to resolve structures and to gain insight into the structure-properties relationship that can be exploited for the design of new materials. During the past few years, there have been a large number of computer simulations to model amorphous structures and to study the mechanical properties of glassy systems. Among the mechanical properties the formation and the evolution of cracks greatly change the performance of every material. The traditional approach to brittle fracture is the study of continuum models, where the stress at the crack tip in an ideally brittle material is singular; since breaking individual bonds at the crack tip is of fundamental importance for crack growth in brittle fracture, it is not clear how accurate a continuum description of brittle fracture is. In strong glasses, which are non-equilibrium systems, the properties depend on the cooling rate at which the sample has been quenched; so the structure is not statistically homogeneous and the local strength may differ from the average value; the stress threshold at which one crack starts to propagate is a random variable and depends almost entirely on the extreme-value statistics of the largest defects. Here we try to connect the theoretical strength, the ageing effects on the mechanical properties and the local fracture toughness distribution in this class of materials.
{"title":"Strength and fracture in strong glasses","authors":"P. G. Gabrielli","doi":"10.1080/13642810208223132","DOIUrl":"https://doi.org/10.1080/13642810208223132","url":null,"abstract":"Abstract The technological relevance of structural glasses has led to increased efforts to resolve structures and to gain insight into the structure-properties relationship that can be exploited for the design of new materials. During the past few years, there have been a large number of computer simulations to model amorphous structures and to study the mechanical properties of glassy systems. Among the mechanical properties the formation and the evolution of cracks greatly change the performance of every material. The traditional approach to brittle fracture is the study of continuum models, where the stress at the crack tip in an ideally brittle material is singular; since breaking individual bonds at the crack tip is of fundamental importance for crack growth in brittle fracture, it is not clear how accurate a continuum description of brittle fracture is. In strong glasses, which are non-equilibrium systems, the properties depend on the cooling rate at which the sample has been quenched; so the structure is not statistically homogeneous and the local strength may differ from the average value; the stress threshold at which one crack starts to propagate is a random variable and depends almost entirely on the extreme-value statistics of the largest defects. Here we try to connect the theoretical strength, the ageing effects on the mechanical properties and the local fracture toughness distribution in this class of materials.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81894647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223136
C. Tomasi, P. Mustarelli, Maria Pilar Infante Garcia, A. Magistris, A. Mandanici
Abstract AgI: AgPO3 glasses are an interesting model system in which to address the relationships between carrier density and mobility, transport mechanism and medium-range order in fast ion-conducting glasses. In this paper we discuss an anomaly observed in the dc conductivity behaviour below room temperature. This anomaly is related to the opening of percolative channels for AgI contents higher than 30 mol % . Solid-state 109 Ag nuclear magnetic resonance (NMR) measurements on the 1:1 AgI: AgPC3 glass allow us to determine the change in the number of mobile carriers over all the temperature region where the anomaly is observed.
{"title":"Low-temperature ionic conductivity in AgI: AgPO3 glasses","authors":"C. Tomasi, P. Mustarelli, Maria Pilar Infante Garcia, A. Magistris, A. Mandanici","doi":"10.1080/13642810208223136","DOIUrl":"https://doi.org/10.1080/13642810208223136","url":null,"abstract":"Abstract AgI: AgPO3 glasses are an interesting model system in which to address the relationships between carrier density and mobility, transport mechanism and medium-range order in fast ion-conducting glasses. In this paper we discuss an anomaly observed in the dc conductivity behaviour below room temperature. This anomaly is related to the opening of percolative channels for AgI contents higher than 30 mol % . Solid-state 109 Ag nuclear magnetic resonance (NMR) measurements on the 1:1 AgI: AgPC3 glass allow us to determine the change in the number of mobile carriers over all the temperature region where the anomaly is observed.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80654132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223125
C. Fusco, P. Gallo, A. Petri, M. Rovere
Abstract We have performed extensive simulations of random sequential adsorption and diffusion of k-mers up to k = 5 on a square lattice with particular attention to the case k = 2. We observe that, for k = 2, 3, complete coverage of the lattice is never reached, because of the existence of frozen configurations that prevent isolated vacancies in the lattice from joining and we argue that complete coverage is never attained for any value of k. In particular the long-time behaviour of the coverage is not mean field and non-analytic, with t −1/2 as the leading term. Morover different values of the diffusion probability and deposition rate lead to different final values of the coverage. We also give a brief account of the vacancy population dynamics.
{"title":"Slow dynamics of k-mers on a square lattice","authors":"C. Fusco, P. Gallo, A. Petri, M. Rovere","doi":"10.1080/13642810208223125","DOIUrl":"https://doi.org/10.1080/13642810208223125","url":null,"abstract":"Abstract We have performed extensive simulations of random sequential adsorption and diffusion of k-mers up to k = 5 on a square lattice with particular attention to the case k = 2. We observe that, for k = 2, 3, complete coverage of the lattice is never reached, because of the existence of frozen configurations that prevent isolated vacancies in the lattice from joining and we argue that complete coverage is never attained for any value of k. In particular the long-time behaviour of the coverage is not mean field and non-analytic, with t −1/2 as the leading term. Morover different values of the diffusion probability and deposition rate lead to different final values of the coverage. We also give a brief account of the vacancy population dynamics.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79840252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223128
L. Andreozzi, M. Bagnoli, M. Faetti, M. Giordano
Abstract The rotational dynamics of the spin probe 2,2,6,6-tetramethyl-piperidin-l-oxyl (TEMPO) dissolved in the molecular glass former phenyl salicylate (Salol) have been investigated via electron spin resonance spectroscopy, in a temperature interval ranging from the supercooled to the glassy state of Salol. The comparison of experimental data with predictions of both diffusive and jump reorientational models has been made. It has been proved that in both the supercooled and the glassy state, the TEMPO spin probe rotates according to a jump process. In the investigated temperature range, the angular jump size Φ has been found to be constant and holds 75°. Moreover, the temperature dependence of the reorientational correlation times, which is well described by a double Arrhenius law, has been studied. The crossing temperature from the first to the second Arrhenius regime is found to be near to the glass transition temperature. Comparison with the results of a previous study on the reorientational dynamics of a TEMPO probe in o-terphenyl, has shown that rotational motion happens in structural cages with comparable free volumes.
{"title":"Jump rotation in a molecular glass former","authors":"L. Andreozzi, M. Bagnoli, M. Faetti, M. Giordano","doi":"10.1080/13642810208223128","DOIUrl":"https://doi.org/10.1080/13642810208223128","url":null,"abstract":"Abstract The rotational dynamics of the spin probe 2,2,6,6-tetramethyl-piperidin-l-oxyl (TEMPO) dissolved in the molecular glass former phenyl salicylate (Salol) have been investigated via electron spin resonance spectroscopy, in a temperature interval ranging from the supercooled to the glassy state of Salol. The comparison of experimental data with predictions of both diffusive and jump reorientational models has been made. It has been proved that in both the supercooled and the glassy state, the TEMPO spin probe rotates according to a jump process. In the investigated temperature range, the angular jump size Φ has been found to be constant and holds 75°. Moreover, the temperature dependence of the reorientational correlation times, which is well described by a double Arrhenius law, has been studied. The crossing temperature from the first to the second Arrhenius regime is found to be near to the glass transition temperature. Comparison with the results of a previous study on the reorientational dynamics of a TEMPO probe in o-terphenyl, has shown that rotational motion happens in structural cages with comparable free volumes.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74972137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223141
L. Cristofolini, M. Fontana, O. Konovalov
Abstract In this paper we study the effect of ultraviolet (UV) illumination on the microscopic structure of molecular layers of a photosensitive fragile polymeric glass former. In particular we show that the increased time relaxation and the reduced mobility of thin molecular multilayers recently reported using high-precision pump-probe ellipsometric experiments correlate with a geometrically induced layering effect which was confirmed by synchrotron X-ray reflectivity experiments. Furthermore the results agree also with recent inelastic-quasielastic neutron scattering measurements of the coupling between the photosensitive side chains and the polymeric main chain. The observed layering is destroyed upon UV illumination. The significance of such results on the glass transition behaviour of this material is discussed.
{"title":"Layering and relaxation in molecular films of a photosensitive polyacrylate from X-ray reflectivity and in elastic neutron scattering experiments","authors":"L. Cristofolini, M. Fontana, O. Konovalov","doi":"10.1080/13642810208223141","DOIUrl":"https://doi.org/10.1080/13642810208223141","url":null,"abstract":"Abstract In this paper we study the effect of ultraviolet (UV) illumination on the microscopic structure of molecular layers of a photosensitive fragile polymeric glass former. In particular we show that the increased time relaxation and the reduced mobility of thin molecular multilayers recently reported using high-precision pump-probe ellipsometric experiments correlate with a geometrically induced layering effect which was confirmed by synchrotron X-ray reflectivity experiments. Furthermore the results agree also with recent inelastic-quasielastic neutron scattering measurements of the coupling between the photosensitive side chains and the polymeric main chain. The observed layering is destroyed upon UV illumination. The significance of such results on the glass transition behaviour of this material is discussed.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75210515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-03-01DOI: 10.1080/13642810208223133
L. Vicari
Abstract Nonlinear optical effects in a water-sodium bis-diethylsulphosuccinate-decane microemulsion near the percolation line and far from critical points are reported and experimentally studied. We use a pump-probe configuration: a probe red Gaussian beam from a He-Ne laser is focused by a converging lens. The Gaussian-shaped TEM00 mode of an Ar+ laser is focused behind a thin film of microemulsion that is located behind the focal plane of the probe. Observation of the temporal behaviour of the detected signal allows one to distinguish a fast negative nonlinear optical effect, attributed to thermal blooming by a slow positive nonlinear optical effect attributed to mass diffusion due to the Soret effect and electrostriction. Maximum nonlinearity is observed for parallel polarizations of the pump and probe beams. Turning off the pump beam, the thermal profile and consequent nonlinear effect disappear. The existence of the concentration profile and of the consequent converging lens effect is clearly detected by the probe beam as well as its slow erasure by thermal diffusion.
{"title":"Pump—probe detection of optical nonlinearity in water-in-oil microemulsion","authors":"L. Vicari","doi":"10.1080/13642810208223133","DOIUrl":"https://doi.org/10.1080/13642810208223133","url":null,"abstract":"Abstract Nonlinear optical effects in a water-sodium bis-diethylsulphosuccinate-decane microemulsion near the percolation line and far from critical points are reported and experimentally studied. We use a pump-probe configuration: a probe red Gaussian beam from a He-Ne laser is focused by a converging lens. The Gaussian-shaped TEM00 mode of an Ar+ laser is focused behind a thin film of microemulsion that is located behind the focal plane of the probe. Observation of the temporal behaviour of the detected signal allows one to distinguish a fast negative nonlinear optical effect, attributed to thermal blooming by a slow positive nonlinear optical effect attributed to mass diffusion due to the Soret effect and electrostriction. Maximum nonlinearity is observed for parallel polarizations of the pump and probe beams. Turning off the pump beam, the thermal profile and consequent nonlinear effect disappear. The existence of the concentration profile and of the consequent converging lens effect is clearly detected by the probe beam as well as its slow erasure by thermal diffusion.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76669861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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