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A mechanism for Pt/SnO(x)-catalyzed CO oxidation is proposed, which is consistent with a broad range of experimental observations. CO oxidation catalysts with high activity at or near room temperature are used in closed-cycle CO2 lasers and air purification.
Oxidation catalysts which operate at ambient temperature were developed for the recombination of carbon monoxide (CO) and oxygen (O2) dissociation products which are formed during carbon dioxide (CO2) laser operation. Recombination of these products to regenerate CO2 allows continuous operation of CO2 lasers in a closed cycle mode. Development of these catalyst materials provides enabling technology for the operation of such lasers from space platforms or in ground based facilities without constant gas consumption required for continuous open cycle operation. Such catalysts also have other applications in various areas outside the laser community for removal of CO from other closed environments such as indoor air and as an ambient temperature catalytic converter for control of auto emissions.
Electromagnetic levitation and electron beam surface melting were employed to study the effects of supercooling and cooling rate on the solidification of Cu-10 wt pct Co alloys. Two major effects were observed in the supercooled alloys: the nucleation of a metastable copper-rich phase which contains 13 wt pct to 20 wt pct Co in samples supercooled between 105 and 150 K and liquid phase separation which occurs in samples supercooled 150 K or more. The microstructure of the electron beam melted surfaces consisted of very fine spheres which were similar to those of the sample supercooled more than 150 K but with a refined microstructure. The results indicate that a dynamic bulk supercooling of 150 K may exist in the molten pool during the solidification of electron beam melted surfaces.
High-resolution spectra of the CO overtone emission in the infrared source SVS 13 are obtained and the individual vibration-rotation lines are resolved for the first time in a young stellar object. The observed FWHM velocity of the lines in the v = 2-0 band is 40 km/s. A fit of the v = 2-0 band head with a single temperature LTE slab model yields an optical depth of 0.3 in the R(51) line and a rotational temperature of about 3500 K. Given the best estimates for the orientation of the SVS 13 outflow, the observed line widths are much smaller than expected for either of the two most favored interpretations for the CO emission: a circumstellar disk or a high-velocity neutral wind.
A progress report on the forward model and CO retrieval algorithm is presented. For the forward model, the fast-transmittance algorithm is discussed including monochromatic calculations, determination of fast-transmittance parameters, and regression errors. Simulations, retrieval technique, and sensitivity of the CO retrieval algorithm are discussed.
Damped composite laminates were fabricated by co-curing viscoelastic damping film with graphite/epoxy prepreg plies. The dynamic response of the damped plates was measured using an impulse response technique and compared with the response of similar undamped laminates. Modal damping was computed from the frequency response data. Micrographs of the damped laminates showed that the damping layers retained their integrity during the fabrication process. The layers significantly increased the damping in the composite laminates. The use of the constrained viscoelastic film as an integral part of composite structures appears to be a feasible approach to passive vibration control. Composite plates manufactured with co-cured damping layers may have commercial applications in cases where light weight, strength, and vibration and noise reduction are important considerations.
Carbon is the fourth most abundant element in the Galaxy with an abundance of approximately 4 x 10(exp -4) relative to hydrogen. Of all abundant metals it is the easiest to observe in the interstellar medium (ISM). Carbon can be found in four dominant forms: dust grains, C 2, C 1, and CO. The latter is the most abundant molecule (next to H2) in molecular clouds. All three gas-phase forms produce strong sub-mm wavelength emission lines and are the principal tracers of the warm and dense neutral phases of the ISM. We calculate the gas-phase abundances of neutral carbon (C 1), ionized carbon (C 2), and carbon monoxide (CO) as a function of cosmic time or redshift z in an idealized scenario of galactic evolution.
Centaurus A (NGC 5128) is a nearby (3 Mpc) elliptical galaxy with a prominent dust lane, extensive radio lobes, and a compact radio continuum source, suggestive of nuclear activity. As a consequence of its peculiar morphology, this merger candidate has been the subject of much attention, particularly at optical wavelengths. Unfortunately the high and patchy extinction in the disk, aggravated by the warped structure of the dust lane, has severely hindered investigations into the properties of the interstellar medium, particularly with regard to the extent of star formation. Here we present a map of the (12)CO J = 2-1 line throughout the dust lane which, when combined with a previously measured (12)CO J = 1-0 map and data on molecular absorption lines observed against the compact non-thermal continuum source, offers insight into the excitation conditions of the molecular gas.
Using the new Aerospace spectrometer on the Kuiper Airborne Observatory, we have obtained observations of the molecular shocks associated with OMC-1. Unexpectedly these observations reveal (b = 1-0) emission from CO at 4.6 microns superposed on a strong continuum. Our observations strongly suggest that both the emission feature and the continuum are produced in molecular shocks. Since the (v = 1-0) band of CO is only excited in high-velocity shocks, we may be observing for the first time the primary driving mechanism in these regions. Even if these features are produced by scattering, the characteristics will provide new constraints on the conditions in and the geometry of the shock regions.
Astrophysical implications of the detection by OSSE of Co-57 gamma radiation from SN 1987A are discussed. By burying the alpha-rich-freezeout portion at deeper gamma depths than in published models, it is shown that it remains barely possible that the bolometric luminosity during days 1200-1800 could derive from Co-57 power without requiring 57/56 production ratios greater than twice solar. Alternative mechanisms which may contribute to the bolometric power at late times are proposed.
The paper demonstrates the high accuracy of line positions derived from improved sets of Dunham coefficients for the four more abundant isotopic species of carbon monoxide - (C-12)(O-16), (C-13)(O-16), (C-12)(O-18), and (C-12)(O-17) - which are present in the sun and in cool stellar atmospheres. These new spectroscopic constants make it possible to predict very accurate positions of CO lines at any J-values, especially at very high rotational excitation (up to J around 135). Earlier proposed identifications of CO lines at large J-values are checked, and some incorrect identifications in sunspot spectra are found. The present accurate line positions are also compared with predictions from other available sets of molecular constants. It is concluded that the present improved sets of molecular constants are the most appropriate to all problems of high-resolution stellar and solar spectroscopy at any J- and v-values, particularly for synthetic spectra of cool stars.
An improved method for retrieving pressure-temperature profiles is described and is used to retrieve profiles of the kinetic-temperature and atmospheric-pressure profiles between 20 and 116 km altitudes and the CO2 and CO volume-mixing ratios between 70 and 116 km, using the IR occultation spectra recorded by the Spacelab 3 atmospheric trace molecular spectroscopy (ATMOS) Fourier transform spectrometer between April 29 and May 6, 1985. Profiles are derived for six ATMOS occultations. The CO2 and CO volume-mixing profiles are compared with previous observations and model predictions. Evidence is found for vibrational non-LTE by analyzing the lines of the (nu-2 + nu-3 - nu-2) (C-12)(O-16) band. Results are used for deriving (C-12)(O-16) (010) vibrational temperatures, which are compared with the retrieved kinetic temperatures and the predictions of non-LTE effects by recent models.
An overview is presented of an observational campaign which will measure (1) the seasonal variations of the CO mixing ratio on the Martian polar cap due to accumulation and depletion of CO during the condensation and evaporation of CO2, as well as (2) the early spring ozone and water vapor of the Martian north polar cap, and (3) the presence of H2CO, H2O2, and SO2. The lines of these compounds will be measured by a combined 4-m telescope and Fourier-transform spectrometer 27097.
A detailed comparison of some properties of CO is given, at the modified coupled-pair functional, single and double excitation coupled-cluster (CCSD), and CCSD(T) levels of theory (including a perturbational estimate for connected triple excitations), using a variety of basis sets. With very large one-particle basis sets, the CCSD(T) method gives excellent results for the bond distance, dipole moment, and harmonic frequency of CO. In a (6s 5p 4d 3f 2g 1h) + (1s 1p 1d) basis set, the bond distance is about 0.005a0 too large, the dipole moment about 0.005 a.u. too small, and the frequency about 6/cm too small, when compared with experimental results.
Laboratory gas-phase photoabsorption cross sections of the CO Cameron 0-0 band and the underlying pseudocontinuum have been measured at a temperature of 147 K and pressures of about 200 mbar, conditions similar to ambient in various planetary and satellite stratospheres in the solar system. A theoretical modeling program has also been used to calculate the band's spectrum. Agreement between the theoretical and the experimental spectra is very good. Models suggest that the observations of the CO Cameron band using the Hubble Space Telescope will be straightforward for Mars, but marginal for Titan.
Ground-based infrared observations of SN 1987A on day 612 after the explosion have yielded resolved line profiles of Co II, Ni I, Fe II at 10.52, 11.31, and 17.94 micron, respectively. The spectra were taken at a resolving power of about 1000 with an array grating spectrometer on the 4 m telescope of Cerro Tololo Inter-American Observatory. Based on the observed line intensities we have estimated the minimum mass of each ion: M(Co II) = (6.0 +/- 1.8) x 10 exp -5 solar mass; M(Ni I) = (1.1 +/- 0.1) x 10 exp -3 solar mass; and M(Fe II) = (8.0 +/- 1.5) x 10 exp -3 solar mass. From these we infer total masses for cobalt, nickel, and iron in the ejecta. The nickel and iron line profiles are markedly asymmetric. We interpret these as arising from two components, one centered on the stellar rest velocity with an approximately 3250 km/s full width, and the second at about +1200 km/s with an approximately 1100 km/s full width. The asymmetry may represent a large-scale fracturing of the ejecta by Rayleigh-Taylor instabilities.
At a growth temperature of 800 C, Co deposited on a Si capping layer exhibits oriented growth on buried CoSi2 grains on Si(111), a process referred to as endotaxy. This occurs preferentially to surface nucleation of CoSi2, provided the thickness of the Si cap is less than a critical value of about 100 nm for deposition rates of 0.003-0.01 nm/s. The steady-state process is modeled using known values of the Co diffusion coefficient and solid solubility in Si, allowing some conclusions to be drawn regarding parameters relevant to CoSi2 epitaxy. Using this technique, single-crystal continuous layers of CoSi2 can be formed under a high-quality Si capping layer.
Rate constants for excitation of CO by collisions with H2O are needed to understand recent observations of comet spectra. These collision rates are closely related to spectral line shape parameters, especially those for Raman Q-branch spectra. Because such spectra have become quite important for thermometry applications, much effort has been invested in understanding this process. Although it is not generally possible to extract state-to-state rate constants directly from the data as there are too many unknowns, if the matrix of state-to-state rates can be expressed in terms of a rate-law model which depends only on rotational quantum numbers plus a few parameters, the parameters can be determined from the data; this has been done with some success for many systems, especially those relevant to combustion processes. Although such an analysis has not yet been done for CO-H2O, this system is expected to behave similarly to N2-H2O which has been well studies; modifications of parameters for the latter system are suggested which should provide a reasonable description of rate constants for the former.