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Metal-alkyl molecules adsorbed on chemically prepared silicon surfaces have been studied using infrared total-internal reflection and ultraviolet transmission spectroscopies, temperature-programmed desorption spectroscopy (TPD), and mass spectroscopy of laser induced desorption (LID) products. For chemisorbed species, the surface hydroxyl groups have been shown to be the prime adsorption sites. In addition, we determined the identity of the chemisorbed species and their fragments under ultraviolet photodissociation. Surface photodissociation was observed to be strongly wavelength dependent at 193 and 248 nm. [ABSTRACT FROM AUTHOR]

Recent developments at the National Institute of Standards and Technology's facility for Spectral Irradiance and Radiance responsivity Calibrations using Uniform Sources (SIRCUS) are presented. The facility is predicated on the use of broadly tunable narrow-band lasers as light sources in two key radiometric calibration applications. In the first application, the tunable lasers are used to calibrate the spectral power responsivities of primary standard detectors against an absolute cryogenic radiometer (ACR). The second function is to calibrate the absolute radiance and irradiance responsivities of detectors with uniform light sources, typically generated by coupling the laser light into integrating spheres. The radiant flux from the uniform sources is determined by the ACR-calibrated primary standard detectors. Together these sources and detectors are used to transfer radiometric scales to a variety of optical instruments with low uncertainties. We describe methods for obtaining the stable, uniform light sources required for low uncertainty measurements along with advances in laser sources that facilitate tuning over broader wavelength ranges. Example applications include the development of a detector-based thermodynamic temperature scale, the calibration and characterization of spectrographs, and the use of a traveling version of SIRCUS (T-SIRCUS) to calibrate large aperture Earth observing instruments and astronomical telescopes. [ABSTRACT FROM AUTHOR]

The Synchrotron Ultraviolet Radiation Facility (SURF III) at the National Institute of Standards and Technology provides a unique opportunity for high-accuracy ultraviolet (UV) to infrared radiometry due to the 70-fold improvement in the uniformity of the magnetic field from the previous generation of SURF. This improvement enables the properties of the output radiation, such as spectral power, angular spread, and polarization, to be more accurately predicted based on the use of the Schwinger’s equation. The radiation from SURF III is completely characterized by only three parameters, the magnetic field, the radius of the electron beam trajectory, and the electron beam current. For radiometry, the calculability of SURF III provides an important standard light source for source intercomparison. In contrast to the widely used blackbody source where the thermal radiation is completely characterized by the temperature and the emissivity of the blackbody walls, synchrotron radiation extends the wavelength range to UV and x ray which is impractical for blackbody sources. At SURF III, a new beamline, beamline 3, is constructed as a white light beamline for source-based radiometry. We describe the design of the new beamline 3 and its front-end high accuracy electron beam current monitor. This monitor not only measures one of the three fundamental parameters, the electron beam current, it also serves as an electron beam diagnostic tool. We also discuss ways to verify the calculability of SURF III using filter radiometers. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The Synchrotron Ultraviolet Radiation Facility (SURF III) at the National Institute of Standards and Technology provides a unique research opportunity in precision measurements with its continuous and calculable radiation stretching from the soft x ray to the far infrared. In response to the rapid development of ultraviolet photodetectors for applications ranging from industrial photolithography to astrophysics, we have developed measurement capabilities to characterize photodetectors with high accuracy. The absolute measurements at SURF III are based on a high-accuracy liquid-helium cooled cryogenic radiometer for measuring the power of the dispersed radiation from SURF III through a monochromator. Typical detector calibration uncertainties achieved at SURF III using cryogenic radiometer is better than 0.5% in the ultraviolet. Equipped with such a tool, we were able to study a variety of ultraviolet detectors and determine their spectral responsivities, surface reflectivities, and the effects of radiation damage. Due to the accuracy of these measurements, the internal quantum efficiencies of the photodetectors can be derived and theoretically modeled to provide information on the mechanism of photo detection. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The recently completed upgrade of the Synchrotron Ultraviolet Radiation Facility (SURF III) at the National Institute of Standards and Technology (NIST) has improved the accuracy of radiometric measurements over a broad spectral range from the infrared to the soft x ray. The beamline 4 at SURF III is a cryogenic-radiometer based radiometric facility for the ultraviolet (UV) spectral range. The upgrade of SURF III has allowed us to use beamline 4 to improve the detector spectral power responsivity scales in the wavelength range from 125 to 320 nm. The achieved combined relative standard uncertainty is better than 0.5% over most of this spectral range. This is a significant improvement over the more than 6% relative standard uncertainty in this spectral range of the current scales maintained at the Spectral Comparator Facility (SCF) in the Optical Technology Division and the Far UV Calibration Facility in the Electron and Optical Physics Division. The new UV scale of beamline 4 was subsequently intercompared and transferred to the SCF and to the Far UV Calibration Facility to improve their UV scales and ensure consistency within NIST. The new scale established at beamline 4 improves NIST's calibration capabilities for environmental monitoring, astrophysics, and the UV industry. The new scale also includes wavelengths such as 193 and 157 nm excimer laser wavelengths, which are of particular interest to the semiconductor photolithography industry. [ABSTRACT FROM AUTHOR]