In this paper we review the properties of infrared sources, setting the synchrotron in perspective among lasers and thermal sources. Synchrotron radiation is ideal for spectroscopy on small samples and has enjoyed extensive utilization throughout the world with some 27 beamlines either in operation or planned. It is a broadband source, which is 1000 times brighter than standard thermal sources. It is polarized, pulsed on the nanosecond scale, highly spatially coherent and is also an absolute source making it possible to perform accurate absorption or reflection measurements. The high brightness makes it ideal for spectroscopy on samples with limited throughput and the main focus has been the realization of very high signal to noise values, not only on small samples, but in the far infrared where the 300 K background is a major contributor to the noise. However, synchrotron radiation is not suitable for high power or non-linear applications. Modern free-electron lasers are up to 8 orders of magnitude brighter than synchrotron radiation at the wavelengths at which they operate.

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.

Infrared microspectrometry, using a synchrotron radiation source, has been developed at Super-ACO (LURE-France). In order to accommodate for constrained horizontal (45 mrad) and vertical (18 mrad) collection angles, a particular care has been devoted to the design and making of the extraction optics, in order to achieve the highest brightness as possible, for small area illumination. Experimentally, a net gain of one hundred in Signal to Noise Ratio has been measured for an upper aperture of 3 X 3 micrometers ². Several applications are currently underway, and some of them, related to Biomedical Science are reported in this paper.

The first of several new infrared beamlines, built on a modified bending magnet port of the NSLS VUV ring, is now operational for mid-infrared microspectroscopy. The port simultaneously delivers 40 mrad by 40 mrad to two separate beamlines and spectrometer endstations designated U10A and U10B. The latter is equipped with a scanning infrared microspectrometer. The combination of this instrument and high brightness synchrotron radiation makes diffraction- limited microspectroscopy practical. This paper describes the beamline's performance and presents quantitative information on the diffraction-limited resolution.

This study presents a Kirkpatrick-Baez mirror system which includes two high-order polynomial bendable mirrors in a Taiwan Light Source (TLS) infrared beamline to create and adjust more accurately collimating images on a focusing point. The source of infrared rays is synchrotron radiation from a TLS bending magnet, so the surface of a vertical focusing mirror (VFM) is designed on an elliptical shape. The Runge-Kutta numerical method is used to compute the optimal high-order polynomial shape of the horizontal focusing mirror (HFM), to focus the horizontal arc source on the point image. The HFM and VFM using 17-4 PH stainless steel substrate without an electroless nickel plate are mechanically bent from planar to the desired fifth-order polynomial shapes with central radii of 3.74 m and 5.43 m by the application of equal couples, respectively. The mirror fabrication process, mechanical design, and the method of adjusting the mirror shape using the Long Trace Profiler measurement system are described. Finally, the roughness of mirrors is 3 angstrom RMS. After the mirrors have been bent, the slope error over 2/3 of clear aperture length (170 mm) was reduced to less than 6.3 (mu) rad RMS.

The design and initial commissioning of the first IR beamline at the ALS has been described previously. We report the final commissioning and first results of the mid-IR spectromicroscopy beamline 1.4.3. In addition, several improvements and two new branchlines are presented. Beamline 1.4.2 is connected to the front end under vacuum and consists of a Bruker Rapid- and Step-Scan vacuum FTIR bench. The modulated light is then coupled into a UHV surface science chamber for grazing incidence reflection studies. Several more external ports are available from the Bruker bench. Beamline 1.4.1 receives light from a separate port on the beamline 1.4 front end and connects to an optical table for photoluminescence and other experiments using photons with energies up to 6 eV.

The Stanford free electron laser center was established to support a broad range of biomedical and materials science research. This paper will begin with an introduction to the Center's capabilities, and then will present brief descriptions of some of the experiments utilizing the transform and diffraction limited tunable picosecond pulses of infrared light from the free electron lasers at the Center. The experiments share the common characteristic that they exploit unique aspects of the FEL beams and would be much more difficult to perform with any other light source.

Significant reductions in the noise of the infrared light have been made at Beamline 1.4.3 infrared source at the Advanced Light Source. The primary source of vibrational noise has been identified as the water system for the storage ring RF system, which is located near the beamline. Modifications to this system have reduced the noise by an order of magnitude. The dominant source of higher frequency noise has been identified as phase noise in the RF master oscillator driving synchrotron oscillations of the beam. We present measurements of the effect of the electron beam motion in a Fourier transform interferometer detector and a discussion of the coupling mechanism to the beam.

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.

The coherent generation of synchrotron radiation by an electron storage ring is predicted for wavelengths equal to or longer than the electron bunch length. With typical bunch lengths of approximately 1 cm, diffraction and chamber- screening effects have so-far blocked observation of coherent radiation from a conventional radiation beam line. In the low-energy, second-generation light source MAX-I, the magnet lattice has been tuned to a small momentum compaction factor, allowing rms bunch lengths as short as 1 mm. Here we report the coherent emission phenomena observed from such a bunch at the infrared beam line attached to the MAX-I ring.

Coherent synchrotron radiation from the NSLS VUV ring has been detected and partially characterized. The observations have been performed at the new far infrared beamline U12IR. The coherent radiation is peaked near a wavelength of 7 mm and occurs in short duration bursts. The bursts occur only when the electron beam current (I) exceeds a threshold value (I_th), which itself varies with ring operating conditions. Beyond threshold, the average intensity of the emission is found to increase as (I-I_th)². The coherent emission implies micro-bunching of the electron beam due to a longitudinal instability.

The existing far infrared spectroscopy beam line at the Daresbury Laboratory Synchrotron Radiation Source (SRS) has been adapted to provide intense collimated radiation for a mid infrared microscope. The SRS beam is focused by the microscope onto an area of the sample only 20 X 30 microns in size and this allows the collection of high fidelity data from samples smaller than 10 microns across. At these dimensions, signal-to-noise is significantly greater than with a conventional infrared source. This new facility is now finding applications with a wide range of users in areas such as materials science, conservation, and biomedicine. As part of a collaboration between Daresbury Laboratory, Nottingham University and University Hospital, Nottingham, the instrument is being applied to investigate the subtle chemical differences which occur between normal and cancerous cells on a cell-by-cell basis. Significant spectral shifts, some of which have previously only been observed in macroscopic samples, can be identified in single cells. The enhanced ability to make such measurements by using synchrotron radiation as the IR source has potential to provide a clearer understanding of the changes occurring in cancerous and pre-cancerous cells.

Infrared (IR) microspectroscopy is an analytical technique that is highly sensitive to the chemical components in bone. The brightness of a synchrotron source permits the examination of individual regions of bone in situ at a spatial resolution superior to that of a conventional infrared source. At Beamlines U10B and U2B at the National Synchrotron Light Source, we are examining the role of bone chemical composition in bone disease. In osteoarthritis (OA), it has been demonstrated that the bone underlying the joint cartilage (subchondral bone) becomes thickened prior to cartilage breakdown. Using synchrotron infrared microspectroscopy, we have examined the chemical composition of the subchondral bone in histologically normal and OA monkeys. Results demonstrate that the subchondral bone of OA monkeys is significantly more mineralized than the normal bone, primarily due to an increase in carbonate concentration in the OA bone. High resolution analysis indicates that differences in carbonate content are uniform throughout the subchondral bone region, suggesting that high subchondral bone carbonate may be a marker for OA. Conversely, increases in phosphate content are more pronounced in the region near the marrow space, suggesting that, as the subchondral bone thickens, the bone also becomes more mineralized. Osteoporosis is a disease characterized by a reduction in bone mass and a skeleton that is more susceptible to fracture. To date, it is unclear whether bone remodeled after the onset of osteoporosis differs in chemical composition from older bone. Using fluorescence-assisted infrared microspectroscopy, we are comparing the composition of monkey bone remodeled at various time points after the onset of osteoporosis (induced by ovariectomy). We find that the chemical composition of bone remodeled one year after ovariectomy and one year prior to necropsy is similar to normal bone. On the other hand, bone remodeled two years after ovariectomy is less mature, indicated by lower mineral/protein ratios and higher acid phosphate content. This immature bone may also be a symptom of slower bone formation rates related to estrogen deficiency.

Ablation of human tissue with an infrared laser tuned to the amide II band of proteins has proven to be especially efficient, with reduced collateral damage. In order to check for a specific non-thermal effect at this wavelength, we have irradiated pig tissues at different frequencies, corresponding to the amide I, amide II and phosphate ones, with a free-electron laser, and analyzed the damaged area using an infrared microspectrometer. The observation of a relative weakening of the relative peak intensity of the amide II band when irradiation has been tuned into its resonant frequency tends to demonstrate that the ablation process should be enhanced due to a resonant denaturation of structural proteins.

Alzheimer's Disease is a neurodegenerative disorder marked by progressive cognitive decline. AD presents with many of the same clinical symptoms as senile dementia, but the diagnosis of AD must be confirmed by post-mortem examination of the morphological and histopathological features of the brain. The two classical lesions found in the cortical and hippocampal regions of the brain are the (beta) -amyloid- bearing neuritic plaques and the intraneuronal neurofibrillary tangles.

A facility for performing time-resolved infrared spectroscopy has been developed at the NSLS, primarily at beamline U12IR. The pulsed IR light from the synchrotron is used to perform pump-probe spectroscopy. We present here a description of the facility and results for the relaxation of photoexcitations in both a semiconductor and superconductor.

The development of the capability for sub-nanosecond time- resolved infrared spectroscopy, combining the broad spectral bandwidths and other well-established advantages of Fourier transform interferometry with the high power, high repetition rate and wide tunability of an electron storage ring-based UV free-electron laser pump, along with the broadband, pulsed, featureless IR continuum of synchrotron radiation from the same storage ring as a probe, is discussed. The capabilities of the system compared to other alternatives for fast, time-resolved infrared spectroscopy are discussed.

The UV-storage ring Free Electron Laser (FEL) operating at Super-ACO is a tunable, coherent and intense (up to 300 mW) photon source in the near-UV range (300 - 350 nm). Besides, it has the unique feature to be synchronized in a one-to-one shot ratio with the Synchrotron Radiation (SR) at the high repetition rate of 8.32 MHz. This FEL + SR combination appears to be very powerful for the performance of pump- probe time-resolved and/or frequency-resolved experiments on the sub-ns and ns time-scales. In particular, there is a strong scientific case for the combination of the recently- commissioned SA5 Infra-Red Synchrotron Radiation beamline with the UV-FEL, for the performance of transient IR- absorption spectroscopy on FEL-excited samples with a Fourier-transform spectrometer coupled with a microscope allowing high spectral and spatial resolution. The principle and interest of the two-color combination altogether with the description of both the FEL and the SA5 IR beamline are presented. The first synchronization signal between the IR and the UV beams is shown. The correct spatial overlap between the UV (FEL) and the IR (SR) photon beams is demonstrated by monitoring via IR-spectro-microscopy the time evolution of a single mineral particulate (kaolinite) under UV-FEL irradiation.

Subtle surface modifications can have profound effects on catalytic and electrocatalytic chemistry. Reflection- Absorption Infrared Spectroscopy (RAIRS) using synchrotron radiation is potentially a very powerful probe of the surface interactions involved provided that sufficiently high quality data can be obtained. The performance of the Daresbury RAIRS facility in its original configuration is illustrated with examples of complex adsorbate systems including trimethylamine adsorbed on Ni{111}, CO coadsorbed with potassium on Cu{110} and formate on Cu{100}. The factors that limited performance are highlighted, and the recent major reconstruction of the station to eliminate these is described.

Synchrotron-based Far-IR Reflection Absorption Spectroscopy has been used to measure the optical response of multi- layers of water adsorbed on a cleaned and annealed Fe₃O₄(100) single crystal thin film on MgO(100) substrate in the grazing incidence geometry. Several features of the composite system have been observed. In particular, two derivative-type bands at 700 and 800 cm^-1 have been attributed to the librations of ice, and an anti-absorption band at 200 cm^-1 has been assigned to be hindered translations of ice.

Infrared spectroscopy of chemisorbed C₆₀ on Ag(111), Au(110) and Cu(100) reveals that a non-IR active mode becomes active upon adsorption and that its frequency shifts proportionally with the charge transferred from the metal to the molecule by about 5 cm^-1 per electron. The temperature dependence of the frequency and the width of this IR feature has also been followed for C₆₀/Cu(100) and was found to agree well with a weak anharmonic coupling (dephasing) to a low frequency mode which we suggest to be the frustrated translational mode of the adsorbed molecules.

Due to its intrinsic high brightness, high stability, and proportionality to the stored electron beam current, synchrotron IR spectroscopy has revealed itself as an unique tool to experimentally test a physical phenomenon that might play an important role at metallic interfaces, the theory for which was motivated by previous observations. Any adsorbate seems to induce an elastic scattering of the conduction electrons, and this reflects in a concomitant broadband IR reflectance change, and a DC resistivity change. By choosing a well-ordered monocrystalline thin film {Cu(111)}, we have checked that the DC resistivity and the asymptotic limit of the IR reflectance changes are linearly dependent, but independent of the nature of the adsorbate. Coadsorption experiments, which have been used to modify the induced density of states at the Fermi level, have further demonstrated that the friction coefficient, which is responsible for the elastic scattering phenomenon, is chemically specific.

One of the key reactions in the CVD growth of SnO₂ on glass is that between SnCl₄ and H₂O. Exploiting the buried metal layer approach, we have used far-infrared RAIRS at the Daresbury synchrotron, to study the initial steps in this process on model glass surfaces, consisting of thin (approximately 500 - 1000 angstroms) SiO₂ films and Na covered SiO₂ films grown on a tungsten substrate.

We have developed a compact Far Infrared Free Electron Laser (FIR FEL) on the base of 8 MEV microtron, which can provide 6 microsecond(s) up to 70 mA macropulse beam current. Beam line consists of bending and steering magnets. Optical Transition Radiation screen and 3 doublets of quadruples to provide matching of microtron output electron beam parameters with optimized parameters for FEL operation. A 2 m length, 25 mm period and 5.7 mm gap undulator has extremely low field error of 0.05% for the magnet field peak amplitude in the range 5.5 - 6.5 kG. Inside the undulator the electron beam passes through 2 mm X 20 mm aperture 2779 mm length planar waveguide. On both sides of the waveguide are installed two cylindrical 3 m curvature mirrors. They form confocal type free space mode in horizontal plane and waveguide mode in vertical plane of the optical resonator. A hole in output mirror provides coupling ratio about 1 - 2%. During experiments we have observed the coherent effect in spontaneous emission with power enhancement approximately 1000 times. It was observed too the long wave radiation, which can be explained by vertical betatron oscillation of electrons in undulator. The experiments with FIR resonator and Ge-Ga liquid He cooled detector shown coherent generation and tunability of it power with tuning of the length of the resonator. The enhancement of outcoupled signal in 50 times was detected with changing of resonator length. This phenomenon can be explained as startup of the lasing process in FIR resonator.