Near infrared reflection spectra of ammonia frost: Interpretation of the upper clouds of Saturn

Models of the uppermost cloud layer on Saturn indicate that the cloud is composed of solid ammonia, with the cloud particles being initially formed at about 150 K, and subsequently transported upward by convection to colder regions of the atmosphere. For the purpose of comparison with Saturn's near-i.r. reflection spectrum, we have obtained laboratory reflection spectra of ammonia frost corresponding to a variety of deposition rates and deposition temperatures.We find that the spectral location of the strong 3 μm absorption band of solid ammonia is highly dependent upon the manner in which the frost layer is formed. For rapid deposition on a 150 K cryosurface, which closely simulates what we believe to be the cloud formation process on Saturn, the band is centered at 3.29 μm. This band location, together with the apparent absence of gaseous ammonia overlying the solid ammonia cloud, is consistent with Saturn's observed reflection spectrum in the vicinity of 3 μm.Comparison of Saturn's reflection spectrum with that of Jupiter, in the vicinity of 1.3 and 1.6 μm, also supports the hypothesis of a Saturnian ammonia ice cloud. Differences in the two observed reflection spectra are interpreted as due to gaseous ammonia absorption bands for Jupiter being replaced by solid ammonia absorption features, at displaced wavelengths, for Saturn.An important conclusion of this study is that, for the purposes of either cloud interpretation or cloud radiation modeling, the polycrystalline phase of solid ammonia, and in turn its spectrum, is highly dependent upon the manner in which the soled is formed.     

Concerning the Range of Olefin Azasulfenation Reaction

A one-pot olefin azasulfenation reaction has been extended to include primary and secondary dialkyldisulfides, as well as ester- and ether-substituted disulfides (methyl dithiodiacetate, ethoxyethyl disulfide). CN-substituted (3-cyanoethyldisulfide), tertiary, benzylic and aromatic disulfides do not undergo this reaction.     

Mössbauer Study of Magnetite Formation by Iron- and Sulfate-Reducing Bacteria

Hyperfine Interactions - Mössbauer investigations of the influence of physicochemical factors and the inert organic substances on the magnetite formation by thermophilic dissimilatory...     

Access to the noryohimban [6,5,6,5,6] ring system via an intramolecular furan Diels-Alder reaction

Polycyclic indolic compounds containing the [6,5,6,5,6] ring system were prepared via an intramolecular furan Diels-Alder reaction of α,β-unsaturated amides generated by the N-acylation of 1-(2-furyl)-β-tetrahydrocarbolines. This chemistry can provide access to D(14)-noryohimban derivatives by exploiting the functionality on the C,D,E ring system of the corresponding cycloadducts.     

New measurements of the infrared spectrum of solid SO2: Applications to IO

We present the results of additional studies of the 6–10 μm spectrum of solid SO₂ formed under a variety of deposition temperatures and deposition rates. Our and other published spectra support the suggestion that absorption by solid SO₂ is a plausible way to reconcile Voyager IRIS observations of Io with models of gas phase absorption by SO₂. Our laboratory spectra also suggest that such solid particles, resulting from condensation of volcanically emitted gaseous SO₂, are formed at a temperature below 110K, although this upper limit apparently conflicts with the work of Savoie and Campbell.     

Mössbauer spectroscopy in studying magnetite formed by iron- and sulfate-reducing bacteria

The kinetics of iron mineral formation by thermophilic dissimilatory iron reducing bacteria using Fe(III) amorphous hydroxide and acetate CH₃COO^? as an electron acceptor and donor, respectively, was investigated by Mössbauer spectroscopy. The effects of various physical and chemical conditions and the presence of an inert organic substance on the formation of biogenic minerals were considered. The production of magnetite due to microbial sulfate reduction by hyperthermophilic dissimilatory sulfate-reducing microorganisms was investigated by Mössbauer spectroscopy methods.