A versatile system for vacuum line synthesis.

  • Dye J.
  • Wayda A.

An extremely versatile greaseless double manifold vacuum line is described. Specific desirable features of the system are its modular construction (allowing complicated apparatus to be quickly assembled and dissembled in a "building block" fashion) and foreground-background pumping capability.

Optical absorption tail in InP:Mn from surface photovoltage.

  • Ballman A.
  • Chiang C.
  • Wagner S.

The steady-state surface photovoltage technique was used to determine the optical absorption tail of InP:Mn, by extrapolation from the above-band gap absorption spectrum. Reaborbed recombination radiation is shown to have no effect on this procedure although it does raise the effective minority carrier diffusion length. The tail absorption coefficient of ...

Ga(0.47)In(0.53)As/InP multiquantum well heterostructure lasers grown by molecular beam epitaxy operation at 1.53 micron.

  • Tsang W.

Current injection Ga(0.47)In(0.53)As/InP multiquantum well heterostructure lasers operating at 1.53 micron have been successfully prepared by molecular beam epitaxy. These lasers consist of four ~70A Ga(0.47)In(0.53)As wells and three ~150A InP barriers. The threshold current density is 2.7 kA/cm(2). In the temperature range of 10-75C, the threshold-temperature dependence can be ...

Deoxyguanosine-deoxyadenosine pairing in the d(C-G-A-G-A-A- T-T-C-G-C-G) duplex: Conformation and dynamics at and adjacent to the dG.dA mismatch site.

  • Ikuta S.
  • Itakura K.
  • Kozlowski S.
  • Patel D.

The dG.dA interaction at position 3 was monitored at the guanosine exchangeable H-1 and non-exchangeable H-8 protons and the non exchangeable adenosine H-2 proton. We demonstrate base pair formation between anti orientations of the guanosine and adenosine rings based on nuclear Overhauser effects observed between the H-2 proton of adenosine ...

Rheological behavior of branched polymer molecules.

  • Helfand E.
  • Pearson D.

The high viscosity and long relaxation time of polymers can be attributed to the entanglements of the molecules in these systems. Entanglement manifests itself effectively as surrounding each molecule by a tube in which lateral motion is constrained. Disentanglement occurs by reptation, motion of the molecules along the tube. These ...

Rayleigh-Brillouin spectroscopy of simple viscoelastic liquids.

  • Carroll P.
  • Patterson G.

The Rayleigh-Brillouin spectrum of 2,4-dimethyl pentane, 2,4,6- trimethyl heptane, 3,5-dimethyl heptane, 2,2,4,4-tetramethyl pentane and 2,2,4,4,6,6,8,8,-octamethyl nonane was measured as a function of temperature from well above the Brillouin linewidth maximum down to the glass transition region. Brillouin splittings and linewidths were determined at each temperature. The results were analyzed quantitatively ...

Oxygen-functionalization of 9-hydroxyphenalenone.

  • Haddon R.

We investigated acyl group transfer in derivatives of 9-hydroxyphenalenone (1,R-H,D). A general scheme for oxygen functionalization of 9-hydroxyphenalenone (1) has proved difficult to achieve, and all previous efforts prepare the acetate (4) have been unsuccessful. The present paper reports the synthesis of 4 and the related compounds 5 and 6 ...

Optical bistability in coupled-cavity semiconductor lasers.

  • Agrawal G.
  • Dutta N.

Coupled-cavity semiconductor lasers are shown to exhibit bistability when both sections operate in the above-threshold region. The hysteresis width can be adjusted by controlling the current in the modulator section. The theoretical model is based on a set of generalized rate equations and shows that the bistable behavior is due ...

Scattering losses in fiber materials: II. Numerical estimates.

  • Lines M.

Applying the theoretical results outlined in the first paper of this series, numerical estimates have been obtained for density fluctuation, Raman, and concentration fluctuation scattering losses in a number of materials which are under consideration as candidates for ultra-low-loss fiber-optic applications. The materials include single component oxide, halide, and chalcogenide ...

Geometry-defined electrical interconnection by a homogeneous medium.

  • Etemad S.
  • Quan X.
  • Sanders N.

We describe a geometry-defined electrical interconnection medium based on a composite of small metal particles dispersed uniformly in an elastomer or adhesive matrix. The volume concentration of metal particles, p, is just below the critical value, p (c), which corresponds to the percolation threshold. The long range electrical conductivity of ...

An in-situ x-ray study of gold/barrier-metal interactions with InGaAsP/InP layers.

  • Temkin H.
  • Vandenberg J.

The effectiveness of barrier metals such as Cr, Ni, Pd, Pt and Ti in gold metallization contacts on InGaAsP/InP was studied. Using a temperature dependent in situ x-ray technique the alloy formation in the contacts was investigated in the temperature range 130C-500C and compared with previous studies on contacts without ...

Linewidth asymmetries in the Mossbauer Zeeman spectrum of amorphous iron-metalloid alloys.

  • Chen H.
  • Eibschutz M.
  • Lines M.

A measurement of the six-line Mossbauer Zeeman spectrum of (57)Fe in Fe(80)B(20) ferromagnetic glass reveals a linewidth asymmetry involving the three line-pairs L(1) and L(7-1), i = 1,2,3. The source of this asymmetry is found to be a positive correlation between isomer shift and hyperfine field and a negative correlation ...

A computerized method for predicted laser emission wavelength using photocurrent spectroscopy.

  • Spector M.

Photocurrent spectra can be used to predict the emission wavelength of lasers made from A1GaAs(DH) wafers. The original work used manually acquired data which was interpreted by a manual method. This memo reports a system for automating both data acquisition and interpretation using numerical differentiation algorithms to characterize the band ...

Improved MOS capacitor measurements using the Q-C method.

  • Brews J.
  • Nicollian E.

We describe a method for determining band bending versus gate bias, doping profile, and oxide charge density by simultaneous measurement of charge and high frequency MOS capacitance as a function of applied voltage. This charge-capacitance or Q-C method is compared with the usual MOS measurements for the same properties. We ...

Continuous operation of monolithic dynamic-single-mode coupled- cavity lasers.

  • Burrus C.
  • Coldren L.
  • Ebeling K.
  • Rentschler J.
  • Wilt D.

The first cw monolithic two-section lasers were fabricated using reactive-ion-etched grooves in buried-crescent wafers. Tunable single-mode selection with spurious mode levels down ~20 dB was demonstrated under modulation.

Measurement of dispersion using short lengths of optical fiber and picosecond pulses from semiconductor film lasers.

  • Stone J.
  • Wiesenfeld J.

Group velocity dispersion spectra have been determined for 7.8-m lengths of single-mode optical fiber. The dispersion spectra are derived from measurement of the transit delay time of picosecond pulses (4-10 ps) from optically-pumped, ultrashort cavity, semiconductor film lasers. The delay time spectra have been measured to 1 ps precision over ...

Reduction of arsenic oxide contamination in molecular beam epitaxy vacuum chambers.

  • Schumaker N.
  • Stall R.
  • Swaminathan V.

Molecular beam epitaxial films of GaAs and Al(x)Ga(1-x)As are degraded by the presence of arsenic oxide in the background gas spectrum. This memorandum discusses a technique for reducing the arsenic oxide contamination by baking the vacuum chamber under a flow of H(2). This technique is useful for an MBE system ...

800 MHz attenuation measured in and around suburban houses.

  • Cox D.
  • Murray R.
  • Norris A.

Signal levels around and within eight suburban houses have been measured at 800 MHz. These measurements are needed in refining the requirements for portable radio communication systems that can accommodate low-power radiotelephone sets. The decrease in median signal level with distance ranges from d(-3) to d(-6.2) for the eight houses. ...

The synthesis and characterization of pure head-to-tail polyfluoroethylenes II. Isoregic polytrifluoroethylene.

  • Cais R.
  • Kometani J.

We report the first synthesis of polytrifluoroethylene (PF (3)E) having a pure head-to-tail (isoregic) sequence of monomer units. The procedure involves reductive debromination or dechlorination of the precursor polymers polybromotrifluoroethylene (PBF(3)E) or polychlorotrifluoroethylene (PCF(3)E). We have also prepared head-to-head, tail-to-tail (syndioregic) PF(3)E by the copolymerization of 1,2-difluoroethylene and tetrafluoroethylene. Regioirregular ...

Conformational origin of the nonequivalent C-13 NMR chemical shifts observed for the isopropyl methyl carbons in branched alkanes.

  • Bovey F.
  • Schilling F.
  • Tonelli A.

The methyl carbons belonging to an isopropyl group attached either to an alkane which possesses a chiral center, or to an achiral alkane lacking a plane of symmetry which bisects the CH(3)-CH-CH(3) angle, can exhibit nonequivalent (13)C NMR chemical shifts. As examples, in 2,4-dimethylhexane, which is chiral, and in 2,4,6-trimethylheptane, ...