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The investigation of phononic collective excitations in soft matter systems at the molecular scale has always been challenging due to limitations of experimental techniques in resolving low-energy modes. Recent advances in inelastic X-ray scattering (IXS) enabled the study of such systems with unprecedented spectral contrast at meV excitation energies. In particular, it has become possible to shed light on the low-energy collective motions in materials whose morphology and phase behavior can easily be manipulated, such as mesogenic systems. The understanding of collective mode behavior with a Q-dependence is the key to implement heat management based on the control of a sample structure. The latter has great potential for a large number of energy-inspired innovations. As a first step toward this goal, we carried out high contrast IXS measurements on a liquid crystal sample, D7AOB, which exhibits solid-like dynamic features, such as the coexistence of longitudinal and transverse phononic modes. For the first time, we found that these terahertz phononic excitations persist in the crystal, smectic A, and isotropic phases. Furthermore, the intermediate smectic A phase is shown to support a van der Waals-mediated nonhydrodynamic mode with an optical-like phononic behavior. The tunability of the collective excitations at nanometer-terahertz scales via selection of the sample mesogenic phase represents a new opportunity to manipulate optomechanical properties of soft metamaterials.

Assessing the fundamental limits of the charge carrier mobilities in organic semiconductors is important for the development of organic electronics. Although devices such as organic field effect transistors (OFETs), organic thin film transistors (OTFTs) and organic light emitting diodes (OLEDs) are already used in commercial applications, a complete understanding of the ultimate limitations of performance and stability in these devices is still lacking at this time. Crucial to the determination of electronic properties in organic semiconductors is the ability to grow ultra-pure, fully ordered molecular crystals for measurements of intrinsic charge transport. Likewise, sensitive tools are needed to evaluate crystalline quality. We present a high-resolution X-ray diffraction and X-ray topography analysis of single-crystals of rubrene that are of the quality being reported to show mobilities as high as amorphous silicon. We show that dislocations and grain boundaries, which may limit charge transfer, are prominent in these crystals.

High-resolution resonant X-ray diffraction experiments have been performed on free-standing films of two selenium-containing antiferroelectric liquid-crystal mixtures. Optical studies had indicated that both mixtures exhibit exceptionally wide intermediate phases, over a total range of > 9 K. Through the structural information obtained from the resonant scattering data, we confirm that the intermediate phases of these mixtures show both 3-layer and 4-layer structural periodicities. Moreover, due to the stability of these phases, we report for the first time the temperature dependence of both the helicoidal pitch and distortion angle in the 3-layer phases deduced using the resonant X-ray technique. Analysis using an extension of the theory set out by Levelut and Pansu (Levelut A-M. and Pansu B., Phys. Rev. E, 60 (1999) 6803) shows that over the temperature ranges measured, the pitch changes linearly as a function of temperature whilst the distortion angle remains constant.

Three experimental measurements have been conducted to investigate the nature of the SmA–SmCα*–SmC* phase transitions of two liquid crystal compounds. The SmA-SmCα* transition shows a continuous transition with XY-like critical exponents. The SmCα*-SmC* transition displays a rapid variation of the incommensurate helical pitch. One of the compounds shows a small jump in the helical pitch, which signals a first order transition and is consistent with high resolution calorimetric results.

We present a new method of sub-Angstrom resolution imaging of the 3D structure of epitaxial films and their interface with the substrate. The method utilizes the diffraction intensities along the substrate-defined Bragg rods and some crude knowledge of the system structure to determine the complex scattering factors (CSFs) along the Bragg rods. The system electron density and the structure is obtained by Fourier transforming the CSFs into real space. We have applied this method to study the structure of a Gd2O3 film and its interface with the GaAs substrate. The results show that the Gd2O3 abandons the bulk stacking order and adopts that of GaAs. Moreover, the atoms in the first few layers move to in-plane positions that overlap those of the underlying Ga and As. This behavior may be at the heart of its ability to passivate GaAs.

With the discovery of the smectic-C(d6)(*) (SmC(d6)(*)) phase showing six-layer periodicity [S. Wang et al., Phys. Rev. Lett. 104, 027801 (2010)] and a recent report of the observation of a possible alternative structure, the need for a reliable and accurate method for distinguishing different possible structures is more urgent than ever. Through simulations using the tensorial structure factor method, we present the resonant x-ray diffraction (RXRD) spectra for different possible structures as proposed in several theoretical studies. Subtle distinctions between models are shown. The ability and limitations of RXRD as a technique for determining the structure of this particular phase is discussed.

We report the observation of x-ray speckle in the reflected beam from Si(111) wafers illuminated at grazing incidence. An intense coherent 8-keV x-ray beam was prepared using a wiggler source and multilayer monochromator optics. We demonstrate that the speckle patterns are specific to the region of the sample that is illuminated. From the trade-off between surface sensitivity and signal as a function of perpendicular momentum transfer, we infer that the speckle is due to the surface morphology on a micrometer length scale. We document and explain the evolution of the speckle patterns from nearly specular at low ${q}_{z}$ to highly structured at larger ${q}_{z}.$

We report the determination of the x-ray diffraction phase in 2D crystals, systems which are periodic in two dimensions and aperiodic in the third. The method consists of measuring the intensity of pairs of parallel, coherent diffracted beams, generated by an incident beam and a beam reflected from a gold mirror layer evaporated on the 2D crystal. Our experiments on an epitaxial GaAs/AlAs heterostructure with aperiodic layering demonstrate that it is possible to measure the phase. This opens the way for direct structural studies of a wide variety of 2D crystals. {copyright} {ital 1997} {ital The American Physical Society}

The high brilliance of third generation undulator sources offers an unprecedented opportunity to perform coherent X-ray diffraction studies of the structure and dynamics of materials on length scales down to interatomic spacings. We have measured the coherent diffraction or “speckle” pattern from a GaAsAlAs superlattice. The speckle diffraction is consistent with height fluctuations of the superlattice of ∼10 A over lengths of order 60 μm. Unlike other methods of characterizing the roughness of semiconductor material, such as scanning probe microscopies (STM, AFM) or scanning electron microscopy (SEM), this novel coherent diffraction method is sensitive to lateral variations of the interface height buried within the small illuminated volume of the material, and thus can offer information unavailable from other non-destructive techniques.

We report x-ray photon correlation spectroscopy studies of the static structure factor and dynamic correlation function of a gold colloid dispersed in the viscous liquid glycerol. We find a diffusion coefficient for Brownian motion of the gold colloid which agrees well with that extrapolated from measurements made with visible light, but which was determined on an optically opaque sample and in a wave-vector range inaccessible to visible light.

Asymmetrically cut perfect crystals, in both the Laue and Bragg geometries, are examined as single crystal monochromators for x‐ray beams that are collimated to a small fraction of the Darwin width, as is typical in experiments with coherent x rays. Both the Laue and asymmetric Bragg geometries are plagued by an inherent chromatic aberration that increases the beam divergence much beyond that of the symmetric Bragg geometry. Measurements from a recent experiment at the ESRF are presented to compare Si(220) (symmetric Bragg), diamond(111) (asymmetric Laue), and diamond(111) (symmetric Bragg inclined) geometries.

The recent discovery of the new smectic-C{sub d6}* (SmC{sub d6}*) phase [S. Wang et al. Phys. Rev. Lett. 104 027801 (2010)] also revealed the existence of a noisy region in the temperature window between the SmC{sub d6}* phase and the smectic-C{sub d4}* (SmC{sub d4}*) phase. Characterized by multiple resonant peaks spanning a wide region in Q{sub Z}, the corresponding structure of this temperature window has been a mystery. In this Letter, through a careful resonant x-ray diffraction study and simulations of the diffraction spectra, we show that this region is in fact an unusually large coexistence region of the SmC{sub d6}* phase and the SmC{sub d4}* phase. The structure of the noisy region is found to be a heterogeneous mixture of local SmC{sub d6}* and SmC{sub d4}* orders on the sub-{micro}m scale.

Electron diffraction has been used to study the freezing in free-standing hexatic B films of several members of the n-alkyl 4′-n-alkyloxybiphenyl-4-carboxylate (nmOBC) homologous series. It was found that 65OBC exhibits the surface crystal E phase and the accompanying orientational epitaxy previously observed in 75OBC. In 46OBC, the surfaces also appear to attain a higher order ahead of the interior, but retain a six-fold symmetry before the entire film abruptly transforms to the crystal E phase. In 3(10)OBC, the behaviour is similar to that of 46OBC, but the film breaks prior to the observation of any crystal E transition.

We describe a simple method and device design that enables fast in-plane electro-optic modulation in conventional nematic liquid crystal (NLC) devices. When combined with optimized NLC materials, this approach yields rotational speeds of 1°/μs (independent of rotation angle, over a wide range) at a moderately low voltage. The observed rotational dynamics indicate that even these high speeds may not represent fundamental physical limits. We demonstrate these ideas in a compact tunable NLC waveplate that uses microelectrodes patterned directly on the tips of optical fibers. These devices offer fast, continuously tunable optic axis with low insertion loss and good performance in the near infrared. Modulators that use this design have promising potential applications for polarization control and analysis in optical communication systems.

We present a new design for mounting a cryogenically cooled Si crystal which gives greatly improved beam stability. The design has been successfully implemented at the University of Michigan, Howard University, Bell Laboratories-Lucent Technologies Collaborative Access Team (MHATT-CAT) 7ID Beamline of the Advanced Photon Source. Before the installation of the new crystal mount, our Si (lll) cryogenically cooled monochromator was sensitive to the pressure fluctuations of the liquid nitrogen coolant, such that the angle of incidence on the first crystal varied linearly with the applied pressure in the cooling lines, causing beam motion of about 250 μm, 60 m from the source. The key element of the design is a symmetrically positioned cooling manifold which balances the forces caused by pressure fluctuations. With this new mount, the typical beam stability is now about 10 μm, comparable to the source stability.

5 pages; International audience; The chiral antiferroelectric structure of an achiral bent-core liquid crystal is characterized by resonant x-ray scattering at chlorine K edge. The "forbidden" reflections resulting from the glide or screw symmetry elements are restored by the anisotropy of the tensor structure factor, which we calculate for two possible structural models. A careful analysis of the polarization states of the restored "forbidden" reflections enables an unambiguous identification of a chiral structure (i.e., the so-called anticlinic, antiferroelectric smectic-Cor Sm-CAPA) coexisting with the achiral synclinic antiferroelectric smectic-C or Sm-CSPA. The method proves to be quite powerful as it identifies the chiral structure within coexisting phases despite an imperfect orientation of the sample. The volume fraction of the chiral phase and the distribution of alignment are extracted from the data.

We report structural results that evidence the polarization distribution of the blocks in the columnar phase of an achiral bent-core liquid crystal. The study was performed using resonant x-ray diffraction at the sulfur K edge on oriented samples aligned on substrates. The extra periodicity is revealed through the violation of the systematic extinction rule of the structural symmetry group along the experimentally accessible diffraction direction. Further data obtained from the polarization analysis of a resonant reflection give information concerning the transition mechanism between B(1) and B(2) phases.

Null transmission ellipsometry and resonant x-ray diffraction are employed to study the effect of enantiomeric excess (EE) on the phase behavior of antiferroelectric liquid crystal 10OTBBB1M7. Phase sequence, layer spacing, and pitch of the helical structures of the smectic-$C$${}_{\ensuremath{\alpha}}^{*}$ and smectic-$C$${}^{*}$ phases are studied as a function of temperature and EE. Upon reducing EE, a liquid-gas-type critical point of the smectic-$C$${}_{\ensuremath{\alpha}}^{*}$ to smectic-$C$${}^{*}$ transition is observed, as well as the disappearance of the smectic-$C$${}_{d4}^{*}$ and the smectic-$C$${}_{d3}^{*}$ phases. Results are analyzed in a mean-field model.

Freeze-fracture transmission electron micrographs of the smectic A(*) phase confirm the twist grain boundary model of Renn and Lubensky. The fracture surface has an undulating structure with a 0.5-micrometer helical pitch parallel to 4.1-nanometer smectic layers. The layers are disrupted by a lattice of screw dislocations oriented normal to the helical axis. Optical diffraction shows that rotation of smectic blocks occurs in discrete steps of about 17 degrees ; hence, the screw dislocations are 14 to 15 nanometers apart and the grain boundaries are 24 nanometers apart. These observations show that the SmA(*) phase is the liquid-crystal analog of the Abrikosov phase in superconductors.

Liquid crystals are intriguing electrically responsive soft matter systems. We report previously unexplored field-induced changes in the structures of some frustrated liquid crystal phases and describe them theoretically. Specifically, we have discovered using resonant x-ray scattering that the four-layer intermediate smectic phase can undergo either a transition to the ferrielectric (three-layer) phase or to the ferroelectric phase, depending on temperature. Our studies of intermediate phases using electric fields offer a way to test theories that describe ferroelectricity in self-assembling fluids.

High-resolution x-ray and optical studies were peformed on oriented samples of the recently discovered smectic-{ital A}{sup *} phase. We confirm that this phase exhibits smectic-{ital A} layers as well as a macroscopic helical strcucture with the helical axis parallel to the layer planes. Furthermore, we demonstrate that the observed scattering can be explained by a cylindrical structure factor that is, within our instrumental resolution, a {delta} function in the radial direction and a Gaussian in the transverse direction as predicted by Renn and Lubensky for the twist grain boundary'' phase.

Employing resonant x-ray diffraction, we observed unique pitch evolutions in the smectic-C{alpha}* phase in mixtures of two antiferroelectric liquid crystals. Our results show that the pitch in this phase continuously evolves across 4 layers, contradicting a theoretical model that predicts that the smectic-C{sub FI2}* phase intervenes in the smectic-C{alpha}* phase. The phase sequences we found can be explained by another model that includes one type of long-range interaction among smectic layers.

Previous results from Kundu using dielectric relaxation have suggested a reentrant antiferroelectric-ferroelectric-antiferroelectric transition in the compound LN36. Our comprehensive studies of this compound using differential optical reflectivity, nonadiabatic scanning calorimetry, null transmission ellipsometry, and resonant x-ray diffraction show that in fact LN36 exhibits the usual phase sequence for chiral smectic liquid crystals: SmA*-SmC*alpha-SmC*-SmC*FI1-SmC*A . Moreover, the SmC*alpha-SmC* transition is a first-order transition, characterized by a discontinuous change in the helical pitch. At temperatures just above the SmC*alpha-SmC* transition, two different values for the helical pitch are simultaneously observed for the first time.

4 pages; International audience; We report the results of resonant x-ray diffraction experiments performed on thick films of a biaxial liquid crystal made of achiral bent-core molecules. Polarization properties of forbidden reflections are observed as a function of the sample rotation angle ' about the scattering vector Q for the first time on a fluid material. The experimental data are successfully analyzed within a tensor structure factor model by taking the nonperfect alignment of the liquid crystal into account. The local structure of the B2 mesophase is hence determined to be SmCSPA.

Employing both null transmission ellipsometry and resonant x-ray diffraction, we confirmed the SmC{sub F12}{sup *}-SmC* phase sequence reversal in one liquid crystal compound and specially prepared binary mixtures. This phase sequence reversal was predicted by two recent theoretical advances. Moreover, the temperature range for the SmC{sub F12}{sup *} phase increases significantly in the mixture suggesting that such a phase sequence may exist in other compounds.

In order to better understand ferroelectricity in thin films, it is important to explore the atomic-scale structure and the spatial distribution of polarization near the interfaces. We present sub-\AA{}ngstrom-resolution electron density maps of three ultrathin ${\mathrm{PbTiO}}_{3}$ films grown epitaxially on ${\mathrm{SrTiO}}_{3}$ (001) substrates. The maps were obtained by analysis of synchrotron x-ray scattering measurements of Bragg rod intensities using the recently developed coherent Bragg rod analysis method. A four- and a nine-unit-cell-thick film were studied at room temperature, and a nine-unit-cell-thick film was studied at 181 \ifmmode^\circ\else\textdegree\fi{}C. The results show that at room temperature, the ${\mathrm{PbTiO}}_{3}$ films are polar, monodomain, and have their polarization oriented away from the substrate. The four-unit-cell film may be the thinnest monodomain perovskite film found to be in the polar phase. At 181 \ifmmode^\circ\else\textdegree\fi{}C, the electron density map of the nine-unit-cell film is consistent with the presence of 180\ifmmode^\circ\else\textdegree\fi{} stripe domains. In the monodomain samples, details of the atomic-scale structure of the ${\mathrm{PbTiO}}_{3}∕{\mathrm{SrTiO}}_{3}$ interface are observed, which may provide evidence for the nature of the positive charge layer required to stabilize polarization in monodomain films.

Design, fabrication, and performance of high speed in-line microcell waveplates based on nematic liquid crystals are reported. These devices show excellent performance when implemented for DOP and SOP measurement and for PMD compensation in 40 Gb/s system tests.

We present Generalized Diffractometer Control (gdc), a diffractometer‐control software package developed specifically for high‐precision measurements of Bragg rods; we discuss its features and analyze its performance in data collection. gdc, implemented at several APS beamlines, controls a six‐circle diffractometer in either Eulerian or kappa geometry, yet does not assume a mechanically ideal diffractometer; instead, the measured directions of the diffractometer axes (and the direction of the incident beam) are input parameters. The Labview‐based program features a graphical interface, making it straightforward to find all the commands and operations. Other features include optimized scans along Bragg rods, straightforward background subtraction, and extensive sets of pseudomotors.

We describe the design, fabrication, and performance of a high-speed, continuously tunable, and reset-free polarization controller based on nematic liquid-crystal (NLC) microcell wave plates fabricated directly between the tips of optical fibers. This controller utilizes a pulsed driving scheme and optimized NLC materials to achieve a stepwise switching speed of 1 deg/micros, for arbitrary rotation angles with moderately low voltages. This compact microcell design requires no bulk optical components and has the potential to have low insertion loss. We describe the performance of these devices when implemented in polarization mode dispersion compensators for 40 Gbit/s systems. The good optical properties and the nonmechanical, high-speed, and low-power operation suggest that this type of device might be considered for some applications in dynamic compensation of polarization mode dispersion, polarization analysis, polarization division demultiplexing, and polarization scrambling in high-speed optical communication systems.

We have used coherent bragg rod analysis (COBRA) to investigate the atomic structure of an epitaxial ${\mathrm{Gd}}_{2}{\mathrm{O}}_{3}$ film grown on a (100) GaAs substrate. COBRA is a method to directly obtain the structure of systems periodic in two dimensions by determining the complex scattering factors along the substrate-defined Bragg rods. The system electron density and atomic structure are obtained by Fourier transforming the complex scattering factors into real space. The results show that the stacking order of the ${\mathrm{Gd}}_{2}{\mathrm{O}}_{3}$ film layers is different from that of cubic bulk ${\mathrm{Gd}}_{2}{\mathrm{O}}_{3}$ and resembles the stacking order of Ga and As layers in GaAs. Furthermore, in the first few ${\mathrm{Gd}}_{2}{\mathrm{O}}_{3}$ layers, Gd atoms are displaced to positions right above the Ga and As positions in the substrate, and they relax towards bulk ${\mathrm{Gd}}_{2}{\mathrm{O}}_{3}$ positions with increasing distance from the interface.

The structures of the liquid crystalline chiral subphases exhibited by several materials containing either a selenium or sulphur atom have been investigated using a resonant x-ray scattering technique. This technique provides a unique structural probe for the ferroelectric, ferrielectric, antiferroelectric, and SmC(*)(alpha) phases. An analysis of the scattering features allows the structural models of the different subphases to be distinguished, in addition to providing a measurement of the helical pitch. This paper reports resonant scattering features in the antiferroelectric hexatic phase, the three- and four-layer intermediate phases, the antiferroelectric and ferroelectric phases and the SmC(*)(alpha) phase. The helicoidal pitch has been measured from the scattering peaks in the four-layer intermediate phase as well as in the antiferroelectric and ferroelectric phases. In the SmC(*)(alpha) phase, an investigation into the helical structure has revealed a pitch ranging from 5 to 54 layers in different materials. Further, a strong resonant scattering signal has been observed in mixtures of a selenium containing material with as much as 90% nonresonant material.

High-resolution resonant polarized x-ray diffraction experiments near the sulfur K edge have been performed on free-standing liquid crystal films exhibiting the chiral smectic-C*FI2 phase. It is widely accepted that this phase has a four-layer repeat unit, but the internal structure of the repeat unit remains controversial. We report different resolved features of the resonant x-ray diffraction peaks associated with the smectic-C*FI2 phase that unambiguously demonstrate that the four-layer repeat unit is locally biaxial about the layer normal and that the measured angle, describing the biaxiality, is in good agreement with optical measurements.

Resonant x-ray scattering has been used to investigate the interlayer ordering of the antiferroelectric and ferrielectric smectic ${C}^{*}$ subphases in a device geometry. The liquid crystalline materials studied contain a selenium atom and the experiments were carried out at the selenium K edge allowing x-ray transmission through glass. The resonant scattering peaks associated with the antiferroelectric phase were observed in two devices containing different materials. It was observed that the electric-field-induced antiferroelectric to ferroelectric transition coincides with the chevron to bookshelf transition in one of the devices. Observation of the splitting of the antiferroelectric resonant peaks as a function of applied field also confirmed that no helical unwinding occurs at fields lower than the chevron to bookshelf threshold. Resonant features associated with the four-layer ferrielectric liquid crystal phase were observed in a device geometry. Monitoring the electric field dependence of these ferrielectric resonant peaks showed that the chevron to bookshelf transition occurs at a lower applied field than the ferrielectric to ferroelectric switching transition.

Resonant x-ray diffraction was carried out at the Se K edge in thick free-standing films of a selenophene liquid crystalline material, revealing detail of the structure of the ferro-, ferri-, and antiferroelectric phases. The ferrielectric phase was shown to have a three-layer superlattice. Moreover, the structure of a lower temperature hexatic phase was established. For the antiferroelectric phase, investigations were also carried out in a planar device configuration. The device allowed resonant scattering experiments to be carried out with and without the application of an electric field and resonant data are compared with electro-optic measurements carried out on the same device.

A workshop on “Soft Matter and Biomolecular Materials: X-ray Scattering Enabled by High Brightness Beamlines” was organized by Ben Hsiao of Stony Brook University and Lin Yang, Elaine DiMasi and Ron Pindak of the NSLS on May 16, 2006. The objective of this workshop was to highlight: (1) recent achievements using synchrotron X-ray scattering for multi-dimensional interrogation of soft matter and biomolecular materials; and (2) creative uses of bright synchrotron beams to obtain spatially and time-resolved structural information. The workshop included several lectures describing cutting-edge synchrotron scattering techniques, such as microbeam small- and wide-angle scattering, grazing-incidence surface scattering, resonant scattering, and fast parallel detection, for studies of polymers, nanoparticles, biomaterials and liquid crystals.

Capturing subtle details at the sub-Angstrom level is key to understanding the structural basis of many intriguing interfacial phenomena in epitaxial thin films and nanostructures. X-ray phase retrieval methods are ideally suited to this task but the usual approaches for determination of uncertainties, based on refining a parametrized model, are not applicable in this case. Here we describe a method to estimate the uncertainties of the system electron density, obtained by phase retrieval, and of parameters of interest obtained from it. The method is based on the bootstrap approach and it can be generally applied to surface x-ray scattering data. Several examples are given which illustrate the method's utility in determining uncertainties arising from random and systematic errors. The approach also provides a quantitative measure of the validity of structural solutions obtained by phase retrieval methods.

We report a type of high-speed microcell polarimeter that utilizes microelectrodes, liquid-crystal films, and ultrathin high-contrast polarizers, all integrated between the tips of two optical fibers. When combined with optimized nematic liquid-crystal materials, this compact (2.5 cm x 0.5 cm x 0.5 cm) device offers excellent optical properties and continuous, high-speed operation at2 kHz with moderately low operating voltages. It requires no bulk optical elements, and it shows excellent performance when implemented for the measurement of degree of polarization in 10-Gbit/s test systems. Polarimeters based on this design have promising potential applications in polarization analysis for high-speed optical communication systems.

This Letter presents x-ray studies of freely suspended smectic liquid-crystal films from 2 to g100 layers thick. Smectic-$B$ thick films of butyloxybenzylidene octylaniline (40.8) have three-dimensional long-range order while thin films are two-dimensional crystals. Large diffuse scattering is observed from soft shear waves, propagating perpendicular to the layers, and three new low-temperature phases with different interlayer order in thick films are found.

The dispersion relations for molecular-orientation fluctuations in a freely suspended ferroelectric smectic-$C$ liquid-crystal film have been determined by inelastic light scattering. The smectic-$C$ film geometry appears to be ideal for the experimental study of the space-time behavior of a two-dimensional orientational field.

Presentation des resultats de mesures experimentales et d'analyses de la theorie de champ moyen sur le comportement de l'angle d'inclinaison moyen pres de la transition smectique A-smectique C

The quenching by an electric field of molecular-orientation fluctuations in freely suspended ferroelectric smectic-$C$ films has been studied by light scattering, allowing absolute measurements of polarization, elastic constants, and viscosities. Evidence is presented to demonstrate surface contributions to Frank elasticity and to show that Frank elasticity is nonlocal.