Eugene B. Bradley

Benchmark circuits for analog and mixed-signal testing

This paper proposes a standard set of fault models and establishes acceptable component variations for a new set of benchmark circuits used to evaluate analog and mixed-signal testing techniques.

New Measurements of the Infrared and the Raman Spectrum of S2Cl2

The Raman spectrum of S2Cl2 has been excited with a 6‐mW He–Ne laser, 6328 A, and new depolarization ratios of the Raman bands have been obtained. The Raman band at 449 cm−1 previously reported by earlier workers is shown to be two bands corresponding to two fundamentals, one of Type A and another Type of B, at 446 cm−1 and 434 cm−1, respectively. The Raman band at 102 cm−1 corresponding to the torsional mode is found to be polarized in disagreement with earlier investigations; the torsional mode is far‐infrared active at 106 cm−1. Three infrared‐active fundamentals and six overtones were observed in the 3000–400 cm−1 region. One of these overtones at 1340 cm−1 has not been reported previously. One Raman overtone band and one Raman combination band have been observed at 858 cm−1 and 647 cm−1, respectively. The Raman and infrared data have been correlated with the right‐angle configuration of C2 symmetry, and thermodynamic properties have been calculated for the liquid state using the harmonic‐oscillator a...

New measurements of the Raman and the IR spectrum of K2Cr2O7

Abstract Raman spectra of a monocrystal of K 2 Cr 2 O 7 and a water solution of K 2 Cr 2 O 7 have been excited with a 6-mW He-Ne laser, 6328A, and new bands and bands splittings have been observed. The far- ir spectrum of the crystal powder in a polyethylene matrix has been obtained from 400–40 cm −1 and six new bands are recorded. In the monocrystal three new Raman bands are seen at 130 cm −1 , 564 cm −1 and 744 cm −1 . The Raman bands observed in the monocrystal correlate well with the earlier ir data up to 556 cm −1 .

Digital components for built-in self-test of analog circuits

We describe the design and operation of a digital test pattern generator (TPG) along with three accumulator based output response analysis (ORA) circuits that are targeted for implementing Built-In Self-Test (BIST) for analog circuits in mixed signal based ASICs. The test patterns produced by the TPG include ramps, triangle and square waves, pseudo-random noise, and a frequency sweep capability for testing the frequency response of the analog circuit under test. The ORA circuits include single and double precision as well as residue accumulators for magnitude and phase measurements. We include an overview of the complete mixed signal based BIST architecture and simulation system along with the results of our initial application of the BIST architecture to an analog circuit under test.

Ultrahigh vacuum chamber for Raman studies of gases adsorbed on metals.

An ultrahigh vacuum chamber is described which is being used to study laser Raman spectra associated with gas adsorption on clean metal surfaces. The system enables sample temperatures from -85 degrees to 600 degrees C to be obtained, and besides surface cleaning capabilities associated with high-temperature oxidation or reduction, it incorporates an Ar(+) sputter gun for surface cleaning. Initial experiments of CO+H(2) adsorption on crystalline Ni surfaces are described and the effects of H(2) and O(2) exposure shown for the 80 cm(-1) band which results from CO+H(2) adsorption.

Normal unenhanced Raman spectra of CO and residual gas adsorbed on Ni(111)

Abstract Normal unenhanced Raman spectra (NURS) of low-polarizability molecules adsorbed on Ni(111) at 98 K. have been recorded at residual gas pressure. This is the first observation of Raman spectra from low-polarizability molecules adsorbed at low pressure onto a poor Raman signal enhancer. Raman bands were also recorded from Ni(111) at 98 and 298 K after exposing the crystal to 106 L CO. Assignments of CO stretches and their corresponding Ni-C stretches are discussed for both linear and bridge CO adsorbed with different neighboring species. Two low-lying vibrational modes of CO were recorded at 80 and 185 cm−1 and assigned to the CNiNi bend (on-top) and the OCNi bend (bridged), respectively. Other Raman bands are assigned to vibrations of oxygen, ozone, and hydrogen adsorbed on Ni(111).

UHV cell for Raman studies of gases adsorbed on metals

We describe a UHV Raman cell for the study by laser Raman spectroscopy of gases adsorbed at low coverages on smooth metal surfaces. Provision is made for three samples, and the sample temperature is controlled from 100 to 800 K. The cell also contains a residual gas analyzer, an argon‐ion sputter gun for cleaning the samples, and ports for observation of right‐angle and oblique Raman scattering. Displayed are Raman spectra of CO on Ni(111) adsorbed from the chamber residual gases and Raman spectra of CH3COCH3 adsorbed on the same single crystal at 10 L exposure.

Reinvestigation of the Raman spectrum of benzophenone using a He-Ne laser

Abstract The Raman spectrum of powdered benzophenone, molten benzophenone, and a solution of benzophenone in methyl alcohol was excited with a He-Ne laser, 6328 A. Thirty-two Raman bands have been observed for the powdered sample, fifteen of which were not reported previously for the powdered sample. Three new bands are observed at 107, 172, and 366 cm −1 in the case of molten benzophenone. Only one carbonyl frequency at 1653 cm −1 is known to be present from this work, in contradiction to two carbonyl frequencies at 1660 and 1708 cm −1 in molten benzophenone, as reported by previous workers. Nineteen Raman bands are reported in the case of a methyl-alcohol solution of benzophenone, fifteen of which are polarized, three depolarized and one weakly polarized. The intensity of several of the Raman bands suggests that this molecule may exhibit stimulated Raman scattering in the solid state.

Theory of surface enhanced Raman scattering

It is now generally accepted that more than one mechanism could be at work in enhancing the Raman signal from molecules adsorbed onto a rough surface. In this paper we present a simple surface coverage, surface roughness dependent model that accounts for one such mechanism. According to our model, each adsorbate is subjected to both polarizing and depolarizing fields from its oscillating neighbors. Competition between these two fields is shown to determine the magnitude of signal enhancement.

New Measurements of the Raman and the Far‐Infrared Spectrum of S2Br2

The Raman spectrum of S2Br2 has been excited with a 6‐mW He–Ne laser operating at 6328 A, and new depolarization ratios of the Raman bands have been obtained. The Raman band at 68 cm−1 corresponding to the torsional mode is found to be polarized in disagreement with an earlier Raman investigation; the torsional mode is far‐infrared active at 70 cm−1. The Raman band at 534 cm−1 is found to be polarized and of type A in contrast to earlier work in which this band was found to be depolarized and of type B. The Raman band at 304 cm−1 is found to be depolarized and of type B whereas in an earlier investigation the band was reported as polarized and of type A. The new Raman and infrared data have been correlated with the right‐angle configuration of C2 symmetry and new assignments have been made. Six coincident Raman‐ and infrared‐active fundamentals are now known from this work and the work of others.