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In this study, a chemical stabilization method, that preserves the tensile strength of artificially aged paper pretreated with an aqueous solution of ionic liquid, is presented. Pure cotton cellulose paper samples were soaked with cholinium glycinate ionic-liquid solution either before or after the artificial aging process, which was based on thermal degradation in dry air. The tensile strength of artificially aged paper was measured by using the double-folding technique. The role of ionic liquids was investigated by mid-infrared and terahertz time-domain absorption spectroscopy. It was found that the tensile strength of pretreated samples is higher than that of other aged samples. A model for changes in the cellulose structure caused by oxidation and by the binding of ionic liquid molecules is proposed, based on the analysis of the mid-infrared absorption bands in the carbonyl/carboxyl region at 1590-1750 cm-1. Terahertz spectroscopy data indicate that the ionic liquid molecules penetrate in the larger size porosity, acting as binders among cellulose fibers to maintain the tensile strength of paper. © 2016 American Chemical Society.

The pH regulation has a fundamental role in several intracellular processes and its variation via exogenous compounds is a potential tool for intervening in the intracellular processes. Proton caged compounds (PPCs) release protons upon UV irradiation and may efficiently provoke intracellular on-command acidification. Here, we explore the intracellular pH variation, when purposely synthesized PCCs are coupled to gold nanoparticles (AuNPs) and dosed to HEK-293 cells. We detected the acidification process caused by the UV irradiation by monitoring the intensity of the asymmetric stretching mode of the CO(2) molecule at 2343 cm(-1). The comparison between free and AuNPs functionalized proton caged compound demonstrates a highly enhanced CO(2) yield, hence pH variation, in the latter case. Finally, PCC functionalized AuNPs were marked with a purposely synthesized fluorescent marker and dosed to HEK-293 cells. The corresponding fluorescence optical images show green grains throughout the whole cytoplasm.

The Raman spectrum of ${\mathrm{Ba}}_{2}{\mathrm{CuGe}}_{2}{\mathrm{O}}_{7}$, a tetragonal insulator which develops Dzyaloshinskii-Moriya helical magnetism below ${T}_{N}=3.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, has been detected at temperatures varying from 300 to 80 K in a single crystal, with the radiation polarized either in the $ab$ plane or along the $c$ axis of its tetragonal cell. Twenty-nine phonon lines out of the 35 allowed by the Raman selection rules for the present geometry were observed, and their vibrational frequencies were found in overall good agreement with those provided by shell-model calculations. Together with the previous report on the infrared-active phonons [A. Nucara et al., Phys. Rev. B 90, 014304 (2014)], the present study provides an exhaustive description, both experimental and theoretical, of the lattice dynamics in ${\mathrm{Ba}}_{2}{\mathrm{CuGe}}_{2}{\mathrm{O}}_{7}$.

The aim of the present work was to investigate how the native signal observed in the electron paramagnetic resonance (EPR) spectrum of tooth enamel and dentin is associated with the organic content of the two tissues. This was achieved by comparing the EPR native signal and the optical bands (Raman and infrared, IR) associated with organic components of tooth enamel and dentin, in natural and deproteinated samples. The main results were: (a) in natural samples, the organic optical bands are more intense in dentin than in enamel, in contrast with the EPR native signal which shows similar intensity in the two tissues; (b) after deproteination, the optical organic bands are completely suppressed in both dentin and enamel, while the EPR native signal is eliminated only in dentin. It is suggested that the IR and Raman organic bands are originated in the bulk of the organic matrix, while the paramagnetic centres associated with the EPR native signal are located in the organic-mineral interface.

First results from the SINBAD beam line at DAΦNE are reported. The SR brilliance, as measured in the far infrared at the sample position, has been compared with the one of the mercury lamp. For λ =100 μm and through an aperture of 1 mm, the gain in intensity is larger than 20. The high brilliance of the synchrotron radiation in the far-infrared is fully exploited by high-pressure experiments. Preliminary experiments with a diamond-anvil cell in the 10 GPa range are reported.

The infrared synchrotron radiation emitted from a bending magnet of the third generation storage ring ELETTRA is studied in detail by ray-tracing techniques. Constant magnetic-field and edge infrared emissions are taken into account in the project of the bending vacuum chamber and on the beamline design. Moreover the gain in flux and brightness with respect to a conventional source of the infrared radiation are calculated and discussed.

The optical reflectivity in the far infrared region (FIR spectra) was measured for five samples of ZnxCd1−xTe in the Zn range 0.056

The synchrotron radiation emitted in the infrared range from a bending magnet of the third generation storage ring ELETTRA is studied in detail by simulation techniques. Edge effects are taken into account. Preliminary experimental checks on an existing port for beam diagnostics are reported. The design of the infrared beamline under construction, including an evaluation of the tolerance on mirror parameters and of thermal distortions, is presented. Finally, the gain in flux and brightness with respect to a conventional source and the polarization degree of the infrared radiation are calculated and discussed.

The pH plays a fundamental role in many biological systems, and it is important to be capable of monitoring and manipulating it. A method for intracellular pH control has been recently developed based on a proton caged compound (PCC), which releases protons upon irradiation with light of proper wavelength. Intracellular modulation of PCC uptake can be achieved by gold nanosized vectors. This, however, is conditioned by the possibility of conjugating PCCs and vectors. Here, we present the synthesis of purposely designed proton caged disulphide sulphonyl urethanes, which bind gold nanoparticles through the disulphide bridge and display photoreactivity through an o-nitrophenyl moiety. The new compounds have been characterized by FTIR, 1H NMR, TEM and TGA and their photoreactivity in the UV range has been probed, after functionalizing them with gold nanoparticles.

${\mathrm{BiMnO}}_{3}$ (BMO), ferromagnetic (FM) below ${T}_{c}\ensuremath{\simeq}100\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, was believed to also be ferroelectric (FE) due to a noncentrosymmetric $C2$ structure, until diffraction data indicated that its space group is the centrosymmetric $C2/c$. Here we present infrared phonon spectra of BMO, taken on a mosaic of single crystals, which are consistent with $C2/c$ at any $Tg10\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, as well as room-temperature Raman data which strongly support this conclusion. We also find that the infrared intensity of several phonons increases steadily for $T\ensuremath{\rightarrow}0$, causing the relative permittivity of BMO to vary from 18.5 at 300 K to 45 at 10 K. At variance with FE materials of the displacive type, no appreciable softening has been found in the infrared phonons. Both their frequencies and intensities, moreover, appear insensitive to the FM transition at ${T}_{c}$.

The lattice dynamics of Ba2CuGe2O7, a compound which develops Dzyaloshinsky-Moriya helical magnetism below TN=3.2 K, has been studied by measuring the infrared reflectivity of a single crystal with the radiation polarized both in the ab plane and along the c axis of its tetragonal cell, from 7 to 300 K. In this compound, where the unit cell has no inversion symmetry, 14 E phonon modes of the ab plane, out of the 18 predicted, and nine B2 modes of the c axis, out of the ten predicted, have been observed. They have been assigned to the atomic motions by a comparison with shell-model calculations, which provided vibrational frequencies in good agreement with the experiment, while most calculated intensities turned out to be much lower than the experimental values. This discrepancy has been tentatively explained by assuming strong electron-phonon interactions, a hypothesis supported by the failure of the f-sum rule if restricted to the phonon region. Indeed, we observe a remarkable increase in the oscillator strengths between 300 and 200 K for the phonons of the ab plane (between 300 and 100 K for the c axis), which implies an increase in the dielectric constant of Ba2CuGe2O7 below room temperature.

Lanthanum manganites with a massive concentration of La defects can be stabilized in the form of thin films, by exploiting the structural stress produced by a substrate such as SrTiO3. They undergo an insulator-to-metal transition (IMT) like those doped by divalent ions, which is here studied by measuring the optical conductivity of LaxMnO films with x = 0.66, 0.88, 0.98 and 1.10, and with , from the far infrared to the near ultraviolet, and between 20 and 300 K. The IMT is here a slow process which continues down to 100 K at least, more than 250 K below its onset at the Curie temperature Tc and at the TIMT measured from the dc resistivity. The metallization is here monitored through the increase of the Drude term and a transfer of spectral weight from a 'hard' midinfrared band MIR-2 peaked between 3000 and 5000 cm−1 at room temperature, to a 'soft' midinfrared band MIR-1 at ~ 1000 cm−1 and to the Drude term. This evidence is in good agreement with a model of phase separation below Tc, where insulating and paramagnetic regions of small polarons coexist with conducting and ferromagnetic regions populated by large polarons and free carriers.

The intrinsic linewidth of Surface Plasmon Polariton resonance in a micrometric metal mesh has been measured with a collimated mid-infrared beam, provided by an External-Cavity, tunable Quantum Cascade Laser. The use of a collimated beam yields a resonance linewidth of 12 cm-1, much narrower than by conventional black-body sources. This opens more favorable perspectives to the use of metal meshes as sensors and detectors.

The interaction between whey carrier protein β-lactoglobulin B and (-)-epicatechin, a major dietary flavonoid with a wide range of health-promoting biological activities, was investigated by Fourier transform infrared spectroscopy in physiological conditions. Amide I spectra of epicatechin - β-lactoglobulin complexes, in D2O buffer solutions, pD= 6.8, at molar ratios from 0.5:1 to 15:1, were measured by using a cell device specifically created. Changes in secondary structure elements at increasing epicatechin concentrations were quantified. Two different trends were observed for the intensities of β-sheet, random coil, and side chain contributions. At molar ratios ≤2 the β-exposed strand contributions (1625 cm−1) increased at the expence of the β-antiparallel sheet band (1637 cm−1). At molar ratios >2 the intensities of both β structures slightly decreased. The same behaviour was observed for the side chain contributions (band around 1610 ÷ 1620 cm−1). In addition, a conformational transition to a slightly opened structure, followed by aggregate formation at the highest molar ratios, were revealed. The results suggest that binding of epicatechin to β-lactoglobulin in physiological conditions occurs at the surface of the protein molecule, resulting in protein dissociation at molar ratios ≤2 with minor changes in secondary structure. This finding provides further evidence for the possibility of successful use of the protein as a carrier of flavonoids, epicatechin included.

The intrinsic linewidth and angular dispersion of Surface Plasmon Polariton resonance of a micrometric metal mesh have been measured with a collimated mid-infrared beam, provided by an External Cavity tunable Quantum Cascade Laser. We show that the use of a collimated beam yields an observed resonance linewidth γ = 12 cm(-1) at the resonance frequency ν0 = 1658 cm(-1), better by an order of magnitude than with a non-collimated beam. The extremely narrow plasmon resonance attained by our mesh is then exploited to reconstruct, by varying the QCL angle of incidence θ, the angular intensity distribution f(θ) of a globar at the focal plane of a conventional imaging setup. We thus show that f(θ) is better reproduced by a Gaussian distribution than by a uniform one, in agreement with ray-tracing simulation.

We report on the approach to extract the infrared and submillimeter radiation out of insertion devices of synchrotron source. In contrast with conventional schemes of extracting large solid angles from a dipole magnet, at the infrared facility in Orsay (SIRLOIN) we realised a design which minimises the heating of the optics and offers advantages including improved stability of the source. Because of the increased brilliance of future synchrotron facilities, these attributes will be required as the important heat load on optics would force out the conventional method of extraction. The performances of SIRLOIN in the infrared and submillimeter domain will be reviewed and some infrared optical experiments will be summarised. In particular, we will discuss: I) investigations of the infrared reflectivity of microcrystals of High-Tc superconductors. II) Vibrational spectroscopy of small clusters trapped in Argon matrices. III) Reconstruction of gold surfaces at the electrochemical interface.

We are developing an all-semiconductor plasmonic platform for mid-infrared sensing which includes growth of epitaxial n-doped germanium films, spectroscopic test and electromagnetic design of plasmonic antennas.

Two beamlines for the use of InfraRed Synchrotron Radiation (IRSR) are presently working in Italy, at the ELETTRA storage ring in Trieste, and at the collider DAFNE in Frascati. A third facility, SPARC in Frascati, has been equipped for the extraction of Terahertz radiation with the aim to perform pump-probe time-domain experiments. Here we describe those apparata and we review the main results that the Italian groups have obtained therein, in recent years, in solid-state physics. We also describe the experiments performed in collaboration with the storage ring BESSY in Berlin, for the exploitation of Coherent Synchrotron Radiation, and the terahertz beam line recently implemented at SPARC, the Free Electron Laser of Laboratori Nazionali di Frascati

The infrared absorption spectrum of solid CD4 has been studied in detail in the frequency range between 2000 and 7000 cm−1. In the three normal‐pressure phases of CD4 between 30 and 2 K, 25 weak overtone and combination bands have been observed. They have been tentatively assigned on the basis of their energies, structures, and intensities. Overtones of order v4 of the bending mode ν4 have been detected for v4=2, 3, 4, 6. As v increases, one observes the transition from a regime where propagating vibrons are created on different molecules, to a regime where multivibron transitions occur on single molecules. Such behavior is triggered by changes in the intramolecular anharmonicity, which plays the role of a vibron–vibron binding energy.

Multiferroic LuFe${}_{2}$O${}_{4}$ (LFO) exhibits three-dimensional (3D) charge order below ${T}_{\text{CO}}\ensuremath{\sim}$ 350 K and strong electroresistance (ER) above a static threshold field ${E}_{\mathrm{th}}$. By measuring simultaneously, in LFO single crystals, the dc current and the far-infrared reflectivity along different axes, we do not detect any insulator-to-metal transition above ${E}_{\mathrm{th}}$. Combined current-temperature measurements confirm that the ER is due to self-heating of LFO, as recently reported. The data can be fit by the standard activation law for an intrinsic semiconductor, with a gap value $\ensuremath{\Delta}$ = 0.57 eV. This value is consistent with that of the optical gap reported for LFO in the literature.

The Q 1 (0) and Q 1 (0)+S 0 (0) infrared bands have been studied in liquid and solid para-H 2 with particular regard to their translational sidebands. In the liquid, their line shapes are well fitted by a model in which the excited particle is encapsulated. In the solid, the phonon sidebands reproduce the main features of the density of states (DOS), as extracted from neutron scattering. The S 1 (0)+S 0 (0) band shows a pure rotonic line shape which is well described by recent DOS calculations

We measure the optical conductivity, σ1(ω), of (SrMnO3)n/(LaMnO3)2n superlattices (SL) for n = 1, 3, 5, and 8 and 10T400 K. Data show a T-dependent insulator to metal transition (IMT) for n ≤ 3, driven by the softening of a polaronic mid-infrared band. At n = 5 that softening is incomplete, while at the largest-period n = 8 compound the MIR band is independent of T and the SL remains insulating. One can thus first observe the IMT in a Manganite system in the absence of the disorder due to chemical doping. Unsuccessful reconstruction of the SL optical properties from those of the original bulk materials suggests that (SrMnO3)n/(LaMnO3)2n heterostructures give rise to a novel electronic state.

The infrared absorption spectrum of CH4 from 4000 to 12 000 cm−1 has been first studied in the solid phases I and II. More than forty overtone and combination bands, up to the sixth order, have been observed. Some of them are weaker by a factor of ≊105 than the infrared fundamentals. The bands have been assigned on the basis of their frequency, structure, and intensity. Features that can be attributed to propagating vibrons have been observed. The rotovibrational lines of molecules at Oh sites of phase II have been resolved in a few bands, and their relative intensities are in excellent agreement with the predictions of the extended James and Keenan model. The results reported here may help to analyze more complicated spectra, as those of CH4 in planetary atmospheres.

The reflectivity of a large LuFe2O4 single crystal has been measured with the radiation field either perpendicular or parallel to the c axis of its rhombohedral structure, from 10 to 500 K, and from 7 to 16 000 cm(-1). The transition between the two-dimensional and the three-dimensional charge order at T-CO=320 K is found to change dramatically the phonon spectrum in both polarizations. The number of the observed modes above and below T-CO, according to a factor-group analysis, is in good agreement with a transition from the rhombohedral space group R (3) over barm to the monoclinic C2/m. In the subterahertz region a peak becomes evident at low temperature, whose origin is discussed in relation with previous experiments.

We review the results obtained on novel superconductors and on materials showing Charge Density Waves (CDW), which have in common the application of the Bardeen-Cooper-Schrieffer theory, by using Coherent synchrotron Radiation as a source for sub-Terahertz spectroscopy. We also present new data on the low-energy excitations of the CDW pahse of multiferroic LuFe(2)O(4).

We present the design, fabrication and experimental tedt of terahertz bandpass filters made of two-dimensional arrays of Al slot dipoles on Si substrate. The filters are obtained through an inexpensive process with full freedom of design and can be easily implemented for applications in THz spectroscopy.

We observe how the charge-ordering (CO) temperature of Nd1/2Sr1/2MnO3 decreases with the external pressure p from 160 K at p = 0 down to 30 K at p ~ 4.5 GPa, by measuring the values p, T where the far-infrared spectral weight of the metallic phase is fully recovered. We thus determine the (p, T) phase diagram of CO in that manganite. We also find that the parameter d(lnTCO)/dp which describes this metallization from the CO phase is equal and opposite to the quantity d(lnTc)/dp which governs the metallization of the paramagnetic state at comparable Curie temperatures Tc, in similar manganites at half doping., Comment: 5 pages, 5 figures, EPL (2010) in press

In a metallic manganite, the substitution of ${\mathrm{Mn}}^{+3}$ by ${\mathrm{Ga}}^{+3}$ locally destroys both the ferromagnetic order and the Jahn--Teller distortion, without heavily affecting the crystal structure. One can thus observe an unusual metal-to-insulator transition, which is induced neither by the temperature nor by changes in the divalent-ion doping. This transition is studied here by comparing the infrared reflectivity of five samples of ${\mathrm{La}}_{2∕3}{\mathrm{Sr}}_{1∕3}{\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}{\mathrm{O}}_{3}$, with $x$ increasing from 0 to 0.30. The dramatic effect of Ga on the transport properties is monitored through the decrease in the number of free carriers and the increase in their effective mass, until a good metal such as ${\mathrm{La}}_{2∕3}{\mathrm{Sr}}_{1∕3}\mathrm{Mn}{\mathrm{O}}_{3}$ is turned into an insulator at all temperatures. A simple model which links the measured optical parameters to the magnetization $M(x,T)$ well describes the behavior of the plasma frequency, the scattering rate, and the midinfrared absorption, throughout the Ga-induced metal-to-insulator transition.

The present work reports on a spectroscopic study of white colour samples collected from Etruscan polychromes on terracotta from the Cerveteri area. In particular, both white-on-red potsherds of the Orientalising period and high-value polychromes of the Archaic period were considered. The white pigment, a fundamental element in this class of artworks, was not clearly identified in previous archaeological and analytical studies, although the use of kaolin was tentatively proposed. Therefore, samples from the Monte Sughereto kaolin quarry in the Cerveteri area were also studied. The results of detailed analyses carried out using micro-Raman spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy first show that the quarry material is a high-purity kaolin containing quartz. Raman results strongly suggest that the same kind of kaolin was employed in the polychromes of the Archaic period. As to white-on red potsherds, infrared results have a key role in showing that the white pigment is a kaolin closely corresponding to the quarry material since a particular kaolin polytype (dickite) is dominant in both cases. The present work thus provides the first definitive identification of the white pigment used in Etruscan polychromes on terracotta from the Cerveteri area, and suggests that the source of kaolin might be the Monte Sughereto quarry.

In the optical conductivity of four different manganites with commensurate charge order (CO), strong peaks appear in the meV range below the ordering temperature T_{CO}. They are similar to those reported for one-dimensional charge density waves (CDW) and are assigned to pinned phasons. The peaks and their overtones allow one to obtain, for La{1-n/8}Ca{n/8}$MnO{3} with n = 5, 6, the electron-phonon coupling, the effective mass of the CO system, and its contribution to the dielectric constant. These results support a description of the CO in La-Ca manganites in terms of moderately weak-coupling and of the CDW theory., Comment: To be published on Phys. Rev. Lett

Infrared spectroscopy and spectromicroscopy have rapidly flourished using the advantages of InfraRed Synchrotron Radiation (IRSR), namely high brightness, broadband emission, linear and circular polarization and pulsed structure. InfraRed (IR) beamlines constructed at all synchrotron facilities provide a unique opportunity for a new class of experiments with significant multidisciplinary impact inaccessible to experimental equipment employing black body (globar) sources.

Summary form only given. This paper presents DAΦNE the electron-positron collider of Laboratori Nazionali di Frascati INFN (Italy), which is operating as a Φ-meson factory for experiments of high energy physics. The high current and low energy of the DAΦNE beam are favourable for extracting infrared synchrotron radiation (IRSR) from bending magnets. SINBAD, the synchrotron infrared beamline at DAΦNE includes an infrared microscope working between 350 and 10000 cm/sup -1/ which is currently employed for the infrared mapping of inhomogeneous solid samples.

In the mid-infrared absorption of Sr{1-x}Ce{x}MnO{3} at low electron doping (x = 0.05), a band at 0.3 eV is fully replaced by another one at 0.9 eV as the system becomes antiferromagnetic (AF) of type $G$. A weaker effect occurs at x = 0.10 for an AF phase of type $C$. One thus directly measures the electron hopping energies for spin parallel and anti-parallel to that of the host ion. The Hund's, crystal-field, and Jahn-Teller splittings for the Mn{3+} ions in a Mn{4+} matrix, can also be derived., Comment: Includes 8 Postscript figures

The first far-infrared absorption spectra of manganite samples at pressures P up to 10 GPa were obtained on La1-xCaxMnO3-y by use of synchrotron radiation. For x=0.25 and 0.20 (y=0), P promotes partial metallization at room temperature through a strong reduction of the insulating gap. An x=0.20 sample with y=0.08 does not show any charge delocalization effect up to 10 GPa. An Urbach-like model of disordered Jahn-Teller wells is shown to well fit the far-infrared band edge and allows one to obtain a reliable pressure dependence of the energy gap.

High-pressure far-infrared absorption measurements carried on three La 1− x Ca x MnO 3− δ samples, exploiting synchrotron radiation are reported. Present data represent the first measurement of this kind performed on manganites. Our results show a pressure-induced charge delocalization effect only in the stoichiometric samples, whereas a complete metallization is not achieved. The pressure dependence of the frequencies of the main phonon bands and of the gap-energy is presented and discussed. An interpretation of our results in terms of a phase separation scenario is also proposed.

Infrared and Raman spectroscopies were employed to study the temperature dependence of the optical phonons of the $\mathrm{Sr}\mathrm{Mn}{\mathrm{O}}_{3}$ manganite in both the hexagonal and the cubic phase. Changes in the phonon spectrum of the hexagonal $\mathrm{Sr}\mathrm{Mn}{\mathrm{O}}_{3}$ (four-layer structure) observed on decreasing temperature indicate that a subtle structural transition occurs in the system between 200 and $100\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. We propose that the transition consists in a change from the four-layer to a six-layer structure, in which the high-temperature crystal symmetry is retained.

The pressure dependence of the phonon spectrum of three La 1 - x Ca x MnO 3 - δ manganites have been studied by means of Far-IR absorption spectroscopy coupled with a Diamond Anvil Cell. The effect of the applied pressure on the charge delocalization have been investigated defining the nature of the metallization process in the low-frequency domain.

One-pot self-assembled hybrid films were synthesized by the cohydrolysis of methyltriethoxysilane and tetraethoxysilane and deposited via dip-coating. The films show a high "defect-free" mesophase organization that extends throughout the film thickness and for domains of a micrometer scale, as shown by scanning transmission electron microscopy. We have defined these films defect-free to describe the high degree of order that is achieved without defects in the pore organization, such as dislocations of pores or stacking faults. A novel mesophase, which is tetragonal I4/mmm (space group), is observed in the films. This phase evolves but retains the same symmetry throughout a wide range of temperatures of calcination. The thermal stability and the structural changes as a function of the calcination temperature have been studied by small-angle X-ray scattering, scanning transmission electron microscopy, and Fourier transform infrared spectroscopy. In situ Fourier transform infrared spectroscopy employing synchrotron radiation has been used to study the kinetics of film formation during the deposition. The experiments have shown that the slower kinetics of silica species can explain the high degree of organization of the mesostructure.

Reflectivity measurements are used to obtain the optical conductivity of three ${\mathrm{La}}_{0.75}{\mathrm{Ca}}_{0.25}{\mathrm{MnO}}_{3\ensuremath{-}y}$ samples annealed under increasingly strong reducing conditions. All three samples are nearly saturated ferromagnets although their Curie temperatures fall progressively from ${T}_{c}=221\mathrm{K}$ to ${T}_{c}=187\mathrm{K}$ with maximum de-oxygenation. The presence of Drude absorption indicates that the unreduced and the slightly reduced samples are electrical conductors below ${T}_{c}.$ However, the most reduced sample manifests an insulatinglike optical conductivity at all temperatures. Thus, ferromagnetism and insulating behavior coexist in the most-reduced sample. This result contradicts the notion that mobile charge carriers of an electrically conducting manganite induce its ferromagnetism. Beyond Drude absorption, midinfrared and near-infrared absorptions are also observed. A midinfrared absorption band is present in all samples. The energy at its peak falls markedly with decreasing temperature. Moreover, near-infrared absorption is found in the nonconducting sample and in the high-temperature insulating phase of the conducting samples. The implications of these findings are discussed in terms of models for properties of doped manganites.

Infrared absorption spectra of the La 0.75 Ca 0.25 MnO 3 manganite have been collected over the spectral range 600-1100 cm m 1 along isobaric paths at P =0,2,4, and 7 GPa in the 240-320 K temperature range. The pressure dependence of the insulator-to-metal transition temperature T IM has been determined from the spectra analysis and the first PT phase diagram of a manganite in the high-pressure regime is presented and discussed.

Novel silicon photonics applications requiring heavy n-type doping have recently driven a great deal of interest towards the phosphorous doping of germanium. In this work we report on infrared reflectance spectroscopy measurements of the electron density in heavily n-type doped germanium layers obtained by stacking multiple phosphorous δ-layers. Here, we demonstrate that the conventional Drude model of the electrodynamic response of free carriers in metals can be adapted to describe heavily doped semiconductor thin films. Consequently, the effect of the electron density on the plasma frequency, scattering rate and complex permittivity can be investigated.

Raman and infrared absorption spectra of ${\mathrm{Mg}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}{\mathrm{B}}_{2}$ have been collected for $0l~xl~0.5$ in the frequency range of the phonon spectrum. The data show a remarkable dependence on the Al content. Raman spectra have been carefully analized and the x dependence of the peak frequency, the width and the intensity of the phonon modes have been obtained. The results allow us to distinguish between two regimes in the low and high Al content regions. In particular the onset of the high Al content phase evidenced in previous structural studies is marked by new spectral components at high frequencies. Finally a connection between the whole of our results and the suppression of the superconducting phase at high Al content is established.

We measured the pressure dependence of the room-temperature infrared absorption spectrum of the pseudocubic La0.75Ca0.25MnO3 manganite. On increasing pressure up to 10 Gpa we observe the increase of a broad band associated with polaronic absorption, which partially screens the high-frequency phonon at high pressures. We also measured absorption spectra of the same sample as a function of temperature, and of the layered Sr1.5La0.5MnO4 manganite as a function of pressure. The comparison between different sets of spectra clearly shows that the increase of the broad-band absorption observed in the La0.75Ca0.25MnO3 manganite is due to a pressure-induced charge delocalization process. However, the metallic state is not achieved at room temperature, at least in the explored pressure range.

This study reviews the various mechanisms exploited to produce infrared synchrotron radiation (IRSR). It shows that at long wavelengths (long when compared to the critical wavelength of the bending magnet in an electron storage ring), the radiation emitted from a bending magnet edge can be brighter than standard synchrotron radiation. For this purpose, we will discuss the various IRSR sources, namely the bending magnets, the wigglers, the undulator and the bending magnet edges. We will then briefly review a high-resolution study of isolated molecules in the far infrared, the detection of a very narrow Drude term in a high- T c superconductor, a description of ultra-high pressure experiments, an investigation of water encapsulated in non-ionic reverse micelles, and finally, a brief review of spatially resolved studies.

The absorption spectra of polycrystalline La 2– x Sr x CuO 4 have been studied in the far-infrared for x =0,0.023, 0.040, 0.051, 0.106 and for 20⩽ T ⩽300 K. The effects of doping and temperature on the a – b plane Cu–O stretching phonon around 680 cm −1 are considered. This in-plane phonon is increasingly shielded by charges injected by doping and is strongly affected by a Fano interaction with an electronic continuum. Basing on similarities with the spectra of Nd 2– x Ce x CuO 4 and on the evolution of the Fano effect with x and T , the continuum is attributed to a polaronic band.

Both the angular and the spectral distribution of the Infrared Synchrotron Radiation emitted by an undulator of Super-ACO have been measured. Structures due to undulator edges, as well as contributions from the edge emission of a bending magnet placed behind the undulator, have been observed. Detailed calculations including all these sources are in excellent agreement with the measurements, provided that both velocity and acceleration terms are considered.

SINBAD, the infrared beamline which extracts radiation from the DA(Phi) NE collider of the Laboratori Nazionali di Frascati, will be operating in the fall of 1999. The optical layout of SINBAD, fully designed by ray tracing simulation, includes six mirrors which transfer and focus the radiation to an interferometer placed more than 20 m from the source. The actual brilliance gain at the entrance of the interferometer has been accurately evaluated by simulating the expected aberrations, the mirror roughness, and diffraction effects.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

SINBAD, the first beamline in Italy designed to work in the far- and mid-infrared region, is being installed on DAΦNE storage ring, the new Φ-factory atLaboratoriNazionali di Frascati. DAΦNE, first injected in September 1997, will work at 0.51 GeV with a beam current in the range 2–5 A. The infrared synchrotron radiation extracted from a bending magnet is expected to be more brilliant than a black body at 2000 K up to three orders of magnitude in the wavelength range 10–1000 µm. The optical layout of SINBAD, fully designed by ray tracing simulation, includes six mirrors placed in a 18 m long beamline. The infrared radiation is first focused on a wedged diamond window and then re-focused on the entrance of aMichelson interferometer. Diffraction effects and mirror roughness, as well as optical aberrations, have been evaluated.