RSI Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Feb 2002

Volume 73, Issue 2, pp. 241-1098

Page 1 of 10 Pages Next Page | Jump to Page
back to top
RSS Feeds
back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

Coaxial ion beam/infrared laser beam spectrometer for investigating infrared spectra of doubly positively charged molecules (molecular dications)

Ramadan Abusen, Simon G. Cox, Andrew D. J. Critchley, Alan N. Hughes, Faye Kemp, Iain R. McNab, Ralph C. Shiell, and Fiona E. Smith

Rev. Sci. Instrum. 73, 241 (2002); http://dx.doi.org/10.1063/1.1428638 (14 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
We have constructed an apparatus for studying the infrared spectra of molecules with a doubly positive charge (molecular dications). The spectroscopic transitions were recorded indirectly by means of observing a change in the fragmentation rate of the molecular dication when a transition was in resonance. The design and performance of the spectrometer are described, with particular emphasis on the sensitivity achieved for detecting infrared spectra and Zeeman split infrared spectra. The operation and calibration of the spectrometer are discussed and sample results for DCl2+ are presented. It is shown that we achieve the maximum possible signal/noise ratio that could be achieved in this type of experiment. © 2002 American Institute of Physics.
Show PACS
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
33.20.Ea Infrared spectra
33.57.+c Magneto-optical and electro-optical spectra and effects

Cavity ring-down spectroscopy in the liquid phase

Shucheng Xu, Guohe Sha, and Jinchun Xie

Rev. Sci. Instrum. 73, 255 (2002); http://dx.doi.org/10.1063/1.1430729 (4 pages) | Cited 30 times

Full Text: | Download PDF

Show Abstract
A new application for cavity ring-down spectroscopic (CRDS) technique using a pulsed polarized light source has been developed in the absorption measurement of liquids for “colorless” organic compounds using both a single sample cell and double sample cells inserted in an optical cavity at Brewster angle. At present an experimental capability of measuring absorption coefficients as small as 2–5×10−7 cm−1 has been demonstrated by measurement of the absorption baselines. The first spectra for CRDS in the liquid phase, the C–H stretching fifth vibrational overtones of benzene in the pure liquid and hexane solution are obtained. The optical absorption length for liquids in both a single sample cell and double sample cells of 1 cm length is up to 900 cm due to multipass of light within an optical cavity. Compared to the thermal lens and optoacoustic spectroscopic techniques, the sensitivity for CRDS mainly depends on the optical absorption path of the sample (single passing path of the sample times multipass times), is not determined by the laser power and the length of the sample cell. The absolute absorption coefficient and band intensity for the sample are determined directly by the spectroscopy. © 2002 American Institute of Physics.
Show PACS
07.60.Rd Visible and ultraviolet spectrometers
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
42.62.Fi Laser spectroscopy
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Millimeter-wave cavity ringdown spectroscopy

N. Gopalsami, A. C. Raptis, and J. Meier

Rev. Sci. Instrum. 73, 259 (2002); http://dx.doi.org/10.1063/1.1435846 (4 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
Laser-based cavity ringdown techniques have demonstrated ultrahigh sensitivities for trace gas detection in the optical and infrared wavelength regions. We have investigated the applicability of the cavity ringdown technique in the millimeter wave region, which is rich in the rotational spectra of molecules. The millimeter-wave system uses a tunable Fabry–Perot cavity that is excited by a continuous-wave, phase-locked source at the W band; a fast PIN diode switch that turns off the excitation after the cavity is tuned to resonance; and a diode detector that records the resonance decay. Proof of concept has been established by measuring the ringdown times with absorbing materials in the cavity and comparing them with theoretical prediction. © 2002 American Institute of Physics.
Show PACS
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
82.80.Ha Analytical methods involving rotational spectroscopy

A new method of scattering-angle scanning for optical beating light scattering spectroscopy

Tsuyoshi Sonehara and Hajime Tanaka

Rev. Sci. Instrum. 73, 263 (2002); http://dx.doi.org/10.1063/1.1433948 (7 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
Heterodyne light scattering spectroscopy is one of the powerful methods used to study the dynamics of density and concentration fluctuations in simple and complex fluids. In conventional optical beating (heterodyne) techniques, however, the beam configuration must be readjusted each time the scattering angle is changed, so as to get the maximum efficiency of the optical mixing of the scattered and the local light. This readjustment process usually takes a long time, and furthermore, leads to the loss of information on the angular dependence of the scattering intensity, which is extremely sensitive to the optical configuration. Here, we report a new method of scattering-angle scanning that is free from the aforementioned problems, which is particularly suitable for optical beating (heterodyne) light scattering spectroscopy. In our method, the maximum optical mixing efficiency between the scattered and the local light can always be maintained amidst change in the scattering angle. Its validity is demonstrated for Rayleigh scattering. Our method also enables us to determine the absolute scattering angle with a very high accuracy, which is particularly important for Brillouin scattering measurements. © 2002 American Institute of Physics.
Show PACS
07.60.Rd Visible and ultraviolet spectrometers
back to top PARTICLE SOURCES, OPTICS and ACCELERATION, DETECTORS

A method for evaluating aberration in the crossover image in mask irradiation optics of electron beam

Yasunari Sohda, Hiroya Ohta, and Norio Saitou

Rev. Sci. Instrum. 73, 270 (2002); http://dx.doi.org/10.1063/1.1431442 (7 pages)

Full Text: | Download PDF

Show Abstract
A method for evaluating aberration in the crossover image in a cell projection lithography system has been developed. In an electron-beam lithography system of projection-type such as a cell projection lithography system, the aberration in the crossover image causes the electron beam to pass off-axis in the electron optics. Optical simulation has quantitatively shown that the aberration in the crossover image causes an electron-beam blur and a positioning error on a writing sample. The evaluating method consists of four square apertures and a mark-detection function in a cell projection system. By measuring each position of the images of the four square apertures on the writing sample at difference focuses, the aberration can be calculated. The field curvature and the astigmatism in a cell projection system were evaluated by using this method. The field curvature agrees with the simulation. In addition, the measurement of the effect of beam alignment is also demonstrated. It is thus concluded that the method can effectively evaluate the aberration in the crossover image. This method is also useful for other projection-type lithographies of charged particles—like ion and electron beams. © 2002 American Institute of Physics.
Show PACS
41.85.Gy Chromatic and geometrical aberrations
85.40.Hp Lithography, masks and pattern transfer
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

Multichannel rf-compensated Langmuir probe array driven by a single bias supply

S. J. Jeon, G. S. Eom, J. H. Kim, and W. Choe

Rev. Sci. Instrum. 73, 277 (2002); http://dx.doi.org/10.1063/1.1427304 (6 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
A multichannel Langmuir probe array driven by a single bias supply was constructed. For the probes to be used in harsh radio frequency (rf) environments, the individual probe has a rf-compensation circuit. For simultaneously obtaining I–V curves from the probe array, shunt resistors were placed between the probe tips and the active terminal of the bias supply. The pickup signal due to the stray capacitance of the signal lines and the shunt resistance is discussed. Modification of the probe bias circuit by utilizing lock-in amplifiers was attempted to obtain the electron energy distribution function. The multichannel probe array and the relevant circuit driven by a single bias supply were successfully tested to obtain plasma parameters from various plasma conditions not only in rf plasma but also in tokamak ohmic plasma. © 2002 American Institute of Physics.
Show PACS
52.70.Ds Electric and magnetic measurements

A vacuum-ultraviolet and x-ray linear camera for high-temperature plasmas

A. Baciero, B. Zurro, K. J. McCarthy, P. Martín, M. C. de la Fuente, and L. Rodríguez-Barquero

Rev. Sci. Instrum. 73, 283 (2002); http://dx.doi.org/10.1063/1.1435844 (6 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
We describe a prototype linear vacuum-ultraviolet x-ray pinhole camera based on the luminescence of a phosphor screen working in reflection mode. The luminescence emitted by the phosphor, in response to radiation selected by a broadband filter, is detected using a 1024 pixel intensified linear array detector. By operating this detector with integration times from 20 to 50 ms, random plasma fluctuations can be smeared out, so that structures related to the magnetic topology can be searched for. © 2002 American Institute of Physics.
Show PACS
52.70.La X-ray and γ-ray measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

On a variational approach to the extraction of quadratures from broadband reflectometry signals

António C. A. Figueiredo and João P. S. Bizarro

Rev. Sci. Instrum. 73, 289 (2002); http://dx.doi.org/10.1063/1.1428637 (9 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
A variational method is employed to retrieve the phase from broadband reflectometry signals. The method yields the so-called in-phase and quadrature components of a signal (the signal quadratures in short), by stipulating that these should have the smallest possible amount of functional variation, whereby the signal carrier frequency is also recovered as a by-product. The variational approach is based on the reasonable assumption that, for given data, the quadratures are expected to be as slow as possible, as they contain the slow modulations of amplitude and phase, while rapid variations are accounted for by the carrier frequency. The advantages and shortcomings of the variational method are discussed, and a pertinent comparison with the analytic signal—recently proposed as a means to extract the phase from broadband reflectometry signals—is also carried out. The application of the variational method to the reflectometry problem is shown to yield results that are similar to those obtained via the analytic signal. The difference is not significant, especially if detailed measurements are not required, but only averaged ones. © 2002 American Institute of Physics.
Show PACS
52.70.Gw Radio-frequency and microwave measurements
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
06.30.Ft Time and frequency
02.30.Xx Calculus of variations

A frame-cooled plasma grid for long pulse operations in a cesium-seeded volume negative ion source

Yukio Fujiwara, Yoshikazu Okumura, Kazuhiro Watanabe, Rusty Trainham, and Claude Jacquot

Rev. Sci. Instrum. 73, 298 (2002); http://dx.doi.org/10.1063/1.1435845 (7 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
A frame-cooled plasma grid for the International Thermonuclear Experimental Reactor (ITER) was designed in view of temperature and stress distributions using three-dimensional numerical simulations. As a material of the plasma grid, copper–chrome–zirconium was examined, since it has high mechanical strength as well as high thermal conductivity. The numerical simulations indicated that the plasma grid would be kept at about 300 °C, which is optimum temperature for negative-ion production. They also indicated that thermal stress in the plasma grid would be less than yield stress. To demonstrate it, a frame-cooled plasma grid, which corresponds to a subsegment of the ITER plasma grid, was fabricated; an experiment was performed with a prototype of an ITER ion source named Kamaboko source. Experimental results showed that its surface temperature is continuously kept at about 300 °C; it was demonstrated that the frame-cooled plasma grid is applicable to long pulse operations, meeting the temperature requirement for the cesium effect. © 2002 American Institute of Physics.
Show PACS
29.25.Ni Ion sources: positive and negative
52.50.Gj Plasma heating by particle beams
28.52.Fa Materials
28.52.Av Theory, design, and computerized simulation
07.77.Ka Charged-particle beam sources and detectors
52.55.Fa Tokamaks, spherical tokamaks
52.75.-d Plasma devices
back to top MICROSCOPY and IMAGING

Color imaging with a low temperature scanning tunneling microscope

Germar Hoffmann, Jörg Kröger, and Richard Berndt

Rev. Sci. Instrum. 73, 305 (2002); http://dx.doi.org/10.1063/1.1433946 (5 pages) | Cited 23 times

Full Text: | Download PDF

Show Abstract
We report on an improved optical design for detecting light emitted from a scanning tunneling microscope (STM). Using a charge coupled device camera and a grating spectrometer a photon detection efficiency of ≈2.5% at 550 nm is achieved and count rates of up to 5×104 counts/nA/s are observed on a noble metal surface and a W tip. Statistically significant spectra from noble metal surfaces are detected in tens of milliseconds. Thus, new modes of measurement become available, which encompass spectroscopic imaging (acquisition of fluorescence spectra at each point of a STM image), and excitation spectroscopy (acquisition of fluorescence spectra while varying the tip–sample bias). Spectroscopic imaging is used to observe gradual changes of the emission spectra as the STM tip approaches a monoatomic step of Ag(111) on a nanometer scale. Excitation spectroscopy with high resolution in both wavelength and bias voltage is demonstrated for a Ag(111) surface. © 2002 American Institute of Physics.
Show PACS
07.60.Rd Visible and ultraviolet spectrometers
07.79.Cz Scanning tunneling microscopes
06.20.F- Units and standards

A simple low-dissipation amplifier for cryogenic STM

S. Urazhdin, S. H. Tessmer, and R. C. Ashoori

Rev. Sci. Instrum. 73, 310 (2002); http://dx.doi.org/10.1063/1.1433951 (3 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
A current sensitive preamplifier designed for low-temperature scanning tunneling microscopy applications is presented. It combines the dc current measurement necessary for the feedback loop operation with a low noise ac measurement used for spectroscopy. The active device is a high electron mobility transistor which was chosen for its low input capacitance and excellent low-temperature performance. The power dissipation of the transistor can be kept at about 10 μW making it compatible with a variety of cryogenic systems. The ac current sensitivity is about 4 fA/√Hz at 4.2 K. © 2002 American Institute of Physics.
Show PACS
84.30.Le Amplifiers
07.79.Cz Scanning tunneling microscopes
07.68.+m Photography, photographic instruments; xerography
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
85.30.Tv Field effect devices

Cross-correlation image tracking for drift correction and adsorbate analysis

B. A. Mantooth, Z. J. Donhauser, K. F. Kelly, and P. S. Weiss

Rev. Sci. Instrum. 73, 313 (2002); http://dx.doi.org/10.1063/1.1427417 (5 pages) | Cited 17 times

Full Text: | Download PDF

Show Abstract
A digital image tracking algorithm based on Fourier-transform cross-correlation has been developed to correct for instrumental drift in scanning tunneling microscope images. A technique was developed to eliminate cumulative tracking errors associated with fractional pixel drift. This tracking algorithm was used to monitor conductance changes associated with different conformations in conjugated molecular switch molecules and to trace the diffusion of individual benzene molecules on Ag{110}. Molecular motions have been tracked for up to 25 h (400 images) of acquisition time. © 2002 American Institute of Physics.
Show PACS
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation

Simultaneous measurement of spatially separated forces using a dual-cantilever resonance-based touch sensor

Jack V. Phan, Robert Hocken, Stuart T. Smith, and Russell G. Keanini

Rev. Sci. Instrum. 73, 318 (2002); http://dx.doi.org/10.1063/1.1431439 (5 pages)

Full Text: | Download PDF

Show Abstract
A simple device for simultaneously measuring two spatially separated contact forces is described. The device uses a monolithic dual-cantilever touch sensor driven by a piezoelectric PZT actuator. A phase-locking method allows measurement of resonant frequency shifts at constant phase, based on the strain response of a second attached PZT. Calibration and force measurement procedures are developed to extract applied contact forces from the dual-cantilever’s coupled, nonlinear response. Based on a preliminary calibration, the present device exhibits maximum relative measurement error on the order of 6%. Procedures for reducing this error are described. © 2002 American Institute of Physics.
Show PACS
07.10.Pz Instruments for strain, force, and torque
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Equivalent-time sampling force microscopy using pulse position modulation method

R. A. Said

Rev. Sci. Instrum. 73, 323 (2002); http://dx.doi.org/10.1063/1.1430549 (7 pages)

Full Text: | Download PDF

Show Abstract
This paper presents a homodyne pulse-sampling electrostatic force microscopy technique using a pulse position modulation method for the noncontact measurement of internal voltage waveforms in integrated circuits. The measurement system operates by monitoring the mechanical deflection of a micromachined probe as it responds to electric forces induced by the circuit voltage waveform. Although the mechanical response of typical probes used in such systems is limited to few kHz, measurement of high frequency repetitive waveforms is enabled by applying a high speed sampling pulse signal to the probe with the pulse position modulated at a rate below the probe mechanical resonance. This results in down conversion of the circuit induced electric force harmonics to within the probe mechanical response, thus allowing the measurement of high frequency signals. The proposed technique is modeled using Fourier analysis of the measurement system response, and is demonstrated by the measurement of a 0.8 Mbit/s digital pattern on a CMOS test pad. The performance of the measurement system is analyzed based on obtained measurements and simulated system response. An analysis of the method capabilities shows a measurement sensitivity of 13 mVrms/√Hz. © 2002 American Institute of Physics.
Show PACS
07.79.-v Scanning probe microscopes and components

Quantitative three-dimensional reconstruction of geometrically complex structures with nanoscale resolution

D. N. Dunn, G. J. Shiflet, and R. Hull

Rev. Sci. Instrum. 73, 330 (2002); http://dx.doi.org/10.1063/1.1430550 (5 pages) | Cited 7 times

Full Text: | Download PDF

Show Abstract
A technique to reconstruct high resolution three-dimensional structural images and chemical maps of geometrically complex features is presented. A focused ion beam microscope is used to collect secondary electron images and secondary ion mass spectroscopy elemental maps as a function of depth in the sample. These images and elemental maps are then used to reconstruct volume images and chemical maps using shape-based interpolative methods with 25 nm lateral resolution and approximately 10 nm depth resolution. From these reconstructions, fundamental parameters such as connectivity, the volume fraction, and surface areas of features of interest can be calculated directly. These techniques open broad new opportunities for understanding three-dimensional structural and chemical relationships in materials research. © 2002 American Institute of Physics.
Show PACS
68.37.Vj Field emission and field-ion microscopy
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.75.+h Mass spectrometers
42.30.Wb Image reconstruction; tomography
02.60.Ed Interpolation; curve fitting
back to top CONDENSED MATTER; MATERIALS

Microwave measurements of the absolute London penetration depth in double-sided YBa2Cu3O7−x thin films on sapphire

A. G. Zaitsev, R. Schneider, G. Linker, F. Ratzel, R. Smithey, P. Schweiss, J. Geerk, R. Schwab, and R. Heidinger

Rev. Sci. Instrum. 73, 335 (2002); http://dx.doi.org/10.1063/1.1435842 (10 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
The absolute values of the London penetration depth λL, were measured in epitaxial (001) YBa2Cu3O7−x (YBCO) thin films prepared by simultaneous sputter deposition on both sides of 3 in. r-cut sapphire wafers buffered with thin (001) CeO2 layers. The measurements were performed by using a technique, which is based on the effect produced on the quality factor Q of a microwave disk resonator by a gold layer deposited on the YBCO electrodes. The observed change of Q can be transformed into λL value with an accuracy determined mainly by the uncertainty of the YBCO film thickness. The λL(T) data obtained by this technique revealed a good agreement with the variation of the resonant frequency with temperature, which is conventionally used for measurements of the variation of the effective London penetration depth ΔλL eff(T) with temperature. At temperatures above ∼60 K this λL(T) dependence was very close to the predictions of the Gorter–Casimir model. At lower temperatures a linear λL(T) behavior was observed with the slope higher for thinner YBCO films. The absolute λL values were higher than those reported in literature for λab (screening currents flow in the crystallographic a–b plane) of YBCO single crystals. For example, our measured λL (4.2 K) values were in the range of 195–220 nm compared to literature data for λab quoted around 140 nm. © 2002 American Institute of Physics.
Show PACS
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.N- Response to electromagnetic fields
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
81.15.Cd Deposition by sputtering

Alternative detection for angle-resolved photoemission spectrometer in ultraviolet range

J. Thomas and I. Pollini

Rev. Sci. Instrum. 73, 345 (2002); http://dx.doi.org/10.1063/1.1430731 (5 pages)

Full Text: | Download PDF

Show Abstract
An angle-resolved photoemission spectrometer for use in the vacuum ultraviolet range has been developed for spectra analysis. The apparatus incorporates a light source, a monochromator equipped with a toroidal grating, a focusing mirror, and hemispherical electron analyzer. We also present a novel method of electron detection which is based on a photon beam modulation mode, followed by analogical or numerical treatment of photoemission signal. © 2002 American Institute of Physics.
Show PACS
07.81.+a Electron and ion spectrometers
07.60.Rd Visible and ultraviolet spectrometers
79.60.-i Photoemission and photoelectron spectra
41.85.Si Particle beam collimators, monochromators

Intensity calibration for low energy photoelectrons based on simultaneous photocurrent measurement

Koichiro Takeuchi and Sukekatsu Ushioda

Rev. Sci. Instrum. 73, 350 (2002); http://dx.doi.org/10.1063/1.1433952 (4 pages)

Full Text: | Download PDF

Show Abstract
We have devised a method of obtaining an absolute intensity calibration for photoemission measurements. The calibration function a(Ek), where Ek is the measured electron kinetic energy, can be derived solely from the experimental data without any uncertain assumptions. The method is based on the relation between the integrated photoemission intensity and the sample current. This method is especially effective for low energy photoelectrons and is applicable even when the sample is biased with respect to the analyzer. © 2002 American Institute of Physics.
Show PACS
79.60.-i Photoemission and photoelectron spectra
06.20.F- Units and standards
07.81.+a Electron and ion spectrometers

A differentially pumped pressure cell for in situ low-energy ion scattering analysis of catalysts during reactions

W. P. A. Jansen, A. W. Denier v. d. Gon, G. M. Wijers, Y. G. M. Rikers, H. H. Brongersma, P. W. v. d. Hoogen, J. A. M. de Laat, T. M. Maas, E. C. A. Dekkers, and P. Brinkgreve

Rev. Sci. Instrum. 73, 354 (2002); http://dx.doi.org/10.1063/1.1433949 (8 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
A differentially pumped pressure cell has been developed to enable in situ low-energy ion scattering (LEIS) analysis of catalysts during chemical reactions. The cell is fully compatible with an electrostatic analyzer and is, therefore, very well suited to study rough, highly dispersed catalysts. The pressure cell is a continuous flow cell (space velocity 1.2×103 s−1) and allows observation of dynamic surface reactions with various, perfectly mixed gases at fully controlled partial pressures and temperatures up to 800 K. The design decreases the pressure gap by three orders of magnitude. This offers ample opportunities such as the determination of specific adsorption sites, surface coverages of different species during reactions, and information on growth processes, poisoning or chemically induced segregation. As an example, an in situ LEIS study of the CO oxidation over Pt is presented. By combining in situ LEIS and quadrupole mass spectroscopy, both the surface and gas composition could be monitored during this reaction. © 2002 American Institute of Physics.
Show PACS
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
68.35.Dv Composition, segregation; defects and impurities
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Application of a multi-element Ge detector in laser pump/x-ray probe time-domain x-ray absorption fine structure

Guy Jennings, Wighard J. H. Jäger, and Lin X. Chen

Rev. Sci. Instrum. 73, 362 (2002); http://dx.doi.org/10.1063/1.1433947 (7 pages) | Cited 8 times

Full Text: | Download PDF

Show Abstract
The characterization and application of a multi-element Ge solid state detector in time-domain laser pump, x-ray probe (LPXP) x-ray absorption fine structure (XAFS) using a third-generation synchrotron source (Advanced Photon Source or APS) are described. In particular, the following problems are discussed: (1) proper handling of high numbers of x-ray photons within a single pulse or pulse cluster, (2) optimizing the incident number of photons, (3) synchronization of the laser pulse, the x-ray pulse and the detector readout, and (4) shaping time and timing requirements of the detector. Based on the study, we estimate the detector efficiency for LPXP-XAFS experiments and identify the problems and possible solutions. © 2002 American Institute of Physics.
Show PACS
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors

Two-axis rotatable magnet in ultrahigh vacuum

F. Heigl, O. Krupin, G. Kaindl, and K. Starke

Rev. Sci. Instrum. 73, 369 (2002); http://dx.doi.org/10.1063/1.1431440 (2 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
We present a rotatable magnet for ultrahigh vacuum (UHV) applications, with a pair of coils for small magnetic fields in the mOe range and an electromagnet for large fields up to 2 kOe. The magnet is based on a mechanism that permits one to exchange electromagnet and coils while keeping the sample in a measurement position. Combined with a rotatable sample, this setup is an excellent tool for in situ studies of magnetism in UHV, in which different techniques are combined. © 2002 American Institute of Physics.
Show PACS
07.55.Db Generation of magnetic fields; magnets
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
84.32.Hh Inductors and coils; wiring

Improved techniques for measurement of superconductivity in diamond anvil cells by magnetic susceptibility

Yuri A. Timofeev, Viktor V. Struzhkin, Russell J. Hemley, Ho-kwang Mao, and Eugene A. Gregoryanz

Rev. Sci. Instrum. 73, 371 (2002); http://dx.doi.org/10.1063/1.1431257 (7 pages) | Cited 11 times

Full Text: | Download PDF

Show Abstract
Recent improvements in magnetic inductive measurements of superconductivity over a broad range of pressures in high-pressure diamond anvils cells are described. A significant increase in sensitivity is obtained by the application of resonant circuits with voltage increasing transformers, allowing an increase in the working frequency of the experimental setup. As a result, superconductivity in samples with linear dimensions as small as 10 μm can be detected. Recent results obtained with this resonant circuit on samples of sulfur at 230 GPa are presented. Further increase in the sensitivity of the experimental setup can be obtained by summing the results of repeated measurements obtained in the same temperature interval. An example is provided by measurements on a small sample of lead. © 2002 American Institute of Physics.
Show PACS
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
74.62.Fj Effects of pressure
74.25.Ha Magnetic properties including vortex structures and related phenomena
62.50.-p High-pressure effects in solids and liquids

Laser absorption spectroscopy with a blue diode laser in an aluminum hollow cathode discharge

H. Scheibner, St. Franke, Samir Solyman, J. F. Behnke, C. Wilke, and A. Dinklage

Rev. Sci. Instrum. 73, 378 (2002); http://dx.doi.org/10.1063/1.1430548 (5 pages) | Cited 13 times

Full Text: | Download PDF

Show Abstract
A GaN-based blue diode laser is employed for laser absorption spectroscopy in an aluminum hollow cathode glow discharge plasma. A Littrow grating stabilized external resonator is used for tuning the wavelength of laser emission. Scanning the wavelength of the laser probes the absorption profile of aluminum transitions yielding ground state aluminum densities. Hyperfine structure has to be taken into account in order to obtain correct temperatures. The diode laser is used to investigate both the temperature and the density of aluminum atoms sputtered from a cathode surface by ion bombardment from the cathode fall region. The blue diode laser allows quick and easy access to aluminum ground state atoms at low costs. © 2002 American Institute of Physics.
Show PACS
52.80.Hc Glow; corona
42.62.Fi Laser spectroscopy
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
back to top CHEMISTRY

Precise analysis of frequency domain photon migration measurement for characterization of concentrated colloidal suspensions

Zhigang Sun, Yingqing Huang, and Eva M. Sevick-Muraca

Rev. Sci. Instrum. 73, 383 (2002); http://dx.doi.org/10.1063/1.1427303 (11 pages) | Cited 20 times

Full Text: | Download PDF

Show Abstract
Frequency domain photon migration (FDPM) is a new method for characterization of concentrated colloidal suspensions using multiply scattered light. The ability of FDPM to determine size and interaction characteristics of the particulate phase of colloidal suspensions depends largely upon the accuracy and precision of FDPM-measured optical properties. In this work, FDPM measurements at multiple modulation frequencies and multiple source-to-detector distances are systematically analyzed for obtaining accurate and precise scattering properties of colloidal suspensions. Two different data analysis methods, multifrequency (MF) nonlinear regression and multidistance (MD) linear regression, and corresponding various strategies for fitting to the optical diffusion equation are investigated. The accuracy and precision of estimated scattering coefficients by different approaches are compared. Results show that MD linear regression with simultaneous regression of average intensity and phase shift or amplitude and phase shift data provides the best data analysis method since it provides not only accurate estimated parameters but also an accurate estimation of their uncertainties. Finally, an important criterion, derived from the photon diffusion model, is proposed for checking the consistency of measurement data and optimizing experimental conditions for FDPM characterization of multiply scattering materials. © 2002 American Institute of Physics.
Show PACS
42.25.Fx Diffraction and scattering
82.70.Dd Colloids
82.70.Kj Emulsions and suspensions

In situ UV/Vis/near-IR diffuse reflection measurement of catalysts at temperatures up to 673 K

M. Thiede and J. Melsheimer

Rev. Sci. Instrum. 73, 394 (2002); http://dx.doi.org/10.1063/1.1430730 (4 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
In situ UV/VIS/near-IR diffuse reflectance spectroscopy can be carried out on catalysts with a suitable microreactor at temperatures up to 673 K. The experimental difficulties in the application of such a reactor at higher temperatures could be solved as follows. Integrating sphere and reactor are connected by a ceramic part of high reflectivity and low thermal conductivity, i.e., the integrating sphere is enlarged. The signal/noise ratio increases by a factor of 2. The standard IR detector was replaced by a temperature-stabilized version. In addition watercooling jackets were mounted at the integrating sphere. The signal/noise ratio in the near-IR region was thus improved by a factor of 2–3 with a very good reproducibility of measurements. To overcome an alteration of catalyst spectra by thermal radiation, a series of reference spectra of quartz powder (SiO2) were recorded at several temperatures. These spectra are used to correct the catalyst spectra by dividing catalyst and SiO2 spectra. © 2002 American Institute of Physics.
Show PACS
82.80.Dx Analytical methods involving electronic spectroscopy
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers
Page 1 of 10 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close