The abundances of constituents of Titan's atmosphere from the GCMS instrument on the Huygens probe.

Saturn's largest moon, Titan, remains an enigma, explored only by remote sensing from Earth, and by the Voyager and Cassini spacecraft. The most puzzling aspects include the origin of the molecular nitrogen and methane in its atmosphere, and the mechanism(s) by which methane is maintained in the face of rapid destruction by photolysis. The Huygens probe, launched from the Cassini spacecraft, has made the first direct observations of the satellite's surface and lower atmosphere. Here we report direct atmospheric measurements from the Gas Chromatograph Mass Spectrometer (GCMS), including altitude profiles of the constituents, isotopic ratios and trace species (including organic compounds). The primary constituents were confirmed to be nitrogen and methane. Noble gases other than argon were not detected. The argon includes primordial 36Ar, and the radiogenic isotope 40Ar, providing an important constraint on the outgassing history of Titan. Trace organic species, including cyanogen and ethane, were found in surface measurements.

Spectroscopic investigations of descloizite.

Descloizite mineral originated from Grootfontein, South West Africa, is used in the present work. The chemical analysis of this mineral reveals the presence of V(2)O(5)=20.94 wt%, CuO=0.45 wt%, FeO in traces. An EPR study of sample confirms the presence of VO(II) and Fe(III). Optical absorption spectrum of descloizite indicates that VO(II) is present in distorted octahedral environment. NIR results are due to water fundamentals.

Electron paramagnetic resonance, optical absorption, IR and Raman spectral studies on pelecypod shell.

Pelecypod shell originated from Kolleru lake of Andhra Pradesh is used in the present work. It contains Mn(II) and Fe(III) in traces. The EPR spectrum of the compound is due to Mn(II) which is in three independent sites. The three g values are evaluated with slight differences. The hyperfine component varies from 9.33 to 9.49mT. The zero field splitting parameter is also ranges from 43.8(1) to 44.1(1)mT. Using the covalence parameter the number of ligands around metal is estimated as 20. In EPR spectrum Fe(III) is identified. The optical absorption spectrum is attributed to Mn(II) in octahedral geometry. Further 10 Dq band is attributed to Fe(II) in the optical absorption spectrum. NIR spectral results are due to water fundamentals, whereas IR and Raman spectrum is due to carbonate ion fundamentals.

Characterisation of bhringaraj and guduchi herb by ICP-MS analysis, optical absorption, infrared and EPR spectroscopic methods.

Leaves of bhringaraj and guduchi herb of Kadapa district of Andhra Pradesh, India, are dried and powdered. ICP-MS analysis of samples indicates that copper is present in both the samples. An EPR study of guduchi sample also confirms the presence of Fe(III) whereas Eclipta alba confirms the presence of Fe(III), Mn(II) and Cu(II). Optical absorption spectrum of guduchi indicates that Cu(II) is present in rhombically distorted octahedral environment. NIR and IR results are due to carbonate fundamentals.

Thermal decomposition studies of the polyhedral oligomeric silsesquioxane, POSSh, and when it is impregnated with the metallocene bis(eta5-cyclopentadienyl)zirconium (IV) dichloride or immobilized on silica.

Thermal decomposition studies of the free polyhedral oligomeric silsesquioxane, POSSh, and when this compound has been impregnated with Cp2ZrCl2 (Cp = eta5-C5H5) or immobilized on SiO2 were conducted using infrared emission spectroscopy (IES) over a 100-1000 degrees C temperature range and by thermogravimetric analysis (TGA). The organic groups in POSS(h) apparently decompose thermally into Si-CH3, Si-H and other fragments. Upon impregnation with Cp2ZrCl2, however, a different thermal decomposition pathway was followed and new infrared emission bands appeared in the 1000-900 cm(-1) region suggesting the formation of Si-O-Zr moieties. When immobilized on SiO2 and subjected to thermal decomposition, the POSSh compound lost its organic groups and the inorganic structure remaining was incorporated into the SiO2 framework.

Optical absorption and EPR studies on beaverite mineral.

The behaviour of transition metal ions in beaverite mineral has been studied by spectroscopic techniques such as electron paramagnetic resonance and absorption spectroscopy in the UV-vis and NIR regions. The ground state of Cu(II) ion in beaverite is confirmed as (2)B(1g) since g(parallel)>g(perpendicular) (2.42>2.097). A resonance noticed at g=2.017 is ascribed to Fe(III) impurity. Two sets of three characteristic bands observed in the optical absorption spectra are assigned to the same transitions, (2)B(1g)-->(2)A(1g), (2)B(1g)-->(2)B(2) and (2)B(1g)-->(2)E(g) of Cu(II) ion in tetragonal field. The presence of Fe(III) bands is supportive evidence for iron impurity in the mineral. Mid infrared spectrum is due to overtones and combination tones of water and hydroxyl groups.

Raman spectroscopic investigation of acetylation of raw cotton.

Raman spectroscopy has been used to investigate raw cotton acetylation using acetic anhydride/4-dimethylaminopyridine (DMAP) catalyst blend without solvent. The Raman data further confirm successful acetylation as shown by FTIR that was demonstrated previously to be highly sensitive for determining the level of acetylation. However, the Raman peaks are much weaker than the FTIR bands. Nevertheless, the variations of the extent of acetylation estimated from both Raman and FTIR spectra with weight percent gain due to acetylation (WPG) were observed to follow the same pattern. The degrees of acetylation calculated from Raman data were also found to increase linearly with that calculated from the more sensitive FTIR technique. Raman technique is thus suitable for further development as an analytical tool for determining the acetylation level of natural cellulose fibres. Raman data have also shown that the acetylation reaction reduces the crystallinity of cotton.

Electron paramagnetic resonance, optical absorption and IR spectroscopic studies of the sulphate mineral apjohnite.

Apjohnite, a naturally occurring Mn-bearing pseudo-alum from Terlano, Bolzano, Italy, has been characterized by EPR, optical, IR and Raman spectroscopy. The optical spectrum exhibits a number of electronic bands around 400 nm due to Mn(II) ion in apjohnite. From EPR studies, the parameters derived, g=2.0 and A=8.82 mT, confirm MnO(H(2)O)(5) distorted octahedra. The presence of iron impurity in the mineral is reflected by a broad band centered around 8400 cm(-1) in the NIR spectrum. A complex band profile appears strongly both in IR and Raman spectra with four component bands around 1100 cm(-1) due to the reduction of symmetry for sulphate ion in the mineral. A strong pair of IR bands at 1681 and 1619 cm(-1) with variable intensity is a proof for the presence of water in two states in the structure of apjohnite.

Investigation of mandelic acid bonding on Pirkle type chromatographic stationary phases by Raman spectroscopy.

The bonding of mandelic acid enantiomers has been studied on benzene-leucine, dinitrobenzene-leucine and dinitrobenzene-phenylalanine type chiral stationary phases connected to zeolite A supports. The pi-donor, pi-acceptor and H-bonding interactions responsible for diastereomer pair formations can be studied under quasi in situ chromatographic conditions by Fourier transform Raman and surface enhanced Raman spectroscopic techniques. Structural differences between diastereomer pairs result in observable spectral differences at a phase load of approx. 50%. It was shown that the decreasing pi-acceptor character of the phase is associated with its increasing capability of H-bond formation. Correlating spectral data to chromatographic results it can be concluded that, in addition to H-bonding as well as to pi-donor-pi-acceptor interactions, steric hindrances due to bulky moieties of either the stationary phase or the analyte molecules are of importance in successful separations.

An epistemic utility approach to coordination in the Prisoner's Dilemma.

A probabilistic model of single-agent decision making is reviewed which accounts for considerations of both correctness and value. The formalism is then extended to decisions involving multiple agents by the use of a joint coordination function. Individual agents are characterized by factoring the coordination function in terms of conditional valuation and belief functions. This formalism is used to explore the parameter space in which cooperative decisions are possible in the Prisoner's Dilemma.

Raman spectroscopy of selected copper minerals of significance in corrosion.

The Raman spectroscopy of selected minerals of the corrosion products has been measured including nantokite, eriochalcite, claringbullite, atacamite, paratacamite, clinoatacamite and brochantite and related minerals. The free energy of formation shows that each mineral is stable relative to copper metal. The mineral, which is formed in copper corrosion, depends on the kinetics and conditions of the reaction. Raman spectroscopy clearly identifies each mineral by its characteristic Raman spectrum. The Raman spectrum is related to the mineral structure and bands are assigned to CuCl stretching and bending modes and to SO stretching modes. Clinoatacamite is identified as the polymorph of atacamite and not paratacamite. Paratacamite is a separate mineral with a similar but different structure to that of atacamite.

Towards a single crystal Raman spectrum of kaolinite at 77 K.

The Raman spectra at 77 K of the hydroxyl stretching of kaolinite were obtained along the three axes perpendicular to the crystal faces. Raman bands were observed at 3616, 3658 and 3677 cm(-1) together with a distinct band observed at 3691 cm(-1) and a broad profile between 3695 and 3715 cm(-1). The band at 3616 cm(-1) is assigned to the inner hydroxyl. The bands at 3658 and 3677 cm(-1) are attributed to the out-of-phase vibrations of the inner surface hydroxyls. The Raman spectra of the in-phase vibrations of the inner-surface hydroxyl-stretching region are described in terms of transverse and longitudinal optic splitting. The band at 3691 cm(-1) is assigned to the transverse optic and the broad profile to the longitudinal optic mode. This splitting remained even at liquid nitrogen temperature. The transverse optic vibration may be curve resolved into two or three bands, which are attributed to different types of hydroxyl groups in the kaolinite.

Raman microscopic study at 300 and 77 K of some pegmatite minerals from the Iveland-Evje area, Aust-Agder, Southern Norway.

The Raman spectra at 300 and 77 K of beryl, columbite-tantalite and topaz single crystals from pegmatites in the Iveland-Evje area are described in detail. The beryl is shown to contain mainly water type I and less of type II in its channels, while CO2 is only a very minor channel constituent. Cooling to 77 K results in minor shifts towards higher wavenumbers for most bands. The Si-O vibrations at 1009 and 1066 cm(-1) show a doubling to four bands at 1015, 1072, 1087 and 1149 cm(-1) due to structural rearrangements in the hexameric rings forming the channels in the beryl crystal structure. In addition a new band becomes visible around 1155 cm(-1). The tantalite could not be analysed in detail due to strong fluorescence. The Raman spectrum of the yellow topaz from Solås is comparable to that of the colourless topaz from Topaz Mountain, Thomas Range, Utah. Upon cooling to 77 K, two OH-stretching bands become visible around 3644 and 3655 cm(-1), which were not observed at room temperature.

Raman spectroscopy of nacrite single crystals at 298 and 77 K.

A Raman microscope in conjunction with a thermal stage has been used to determine the Raman spectra of single crystals of nacrite at 298 and 77 K. The spectra obtained are a function of the physics of the spectrometer and were orientation dependent. Bands are observed at 3710, 3646, 3630 and 3623 cm(-1). Upon obtaining the Raman spectra at liquid nitrogen temperature, the band at 3648 cm(-1) was not observed but an additional band at 3603 cm(-1) appeared. This latter band may be attributed to the hydroxyl stretching of non-hydrogen bonded interlayer hydroxyls in the nacrite. The bands attributed to both the inner and inner surface hydroxyls moved to lower frequencies upon cooling to liquid nitrogen temperatures. Low frequency bands also showed orientation dependence.

Vibrational spectroscopy of ferruginous smectite and nontronite.

A comparison is made between the Raman and infrared spectra of ferruginous smectite and a nontronite using both absorption and emission techniques. Raman spectra show hydroxyl stretching bands at 3572, 3434, 3362, 3220 and 3102 cm(-1). The infrared emission spectra of the hydroxyl stretching region are significantly different to the absorption spectrum. These differences are attributed to the loss of water, absent in the emission spectrum, the reduction of the samples in the spectrometer and possible phase changes. Dehydroxylation of the two minerals may be followed by the loss of intensity of the hydroxyl stretching and hydroxyl deformation frequencies. Hydroxyl deformation modes are observed at 873 and 801 cm(-1) for the ferruginous smectite, and at 776 and 792 cm(-1) for the nontronite. Raman hydroxyl deformation vibrations are found at 879 cm(-1). Other Raman bands are observed at 1092 and 1032 cm(-1), assigned to the SiO stretching vibrations, at 675 and 587 cm(-1), assigned to the hydroxyl translation vibrations, at 487 and 450 cm(-1), attributed to OSiO bending type vibrations, and at 363, 287 and 239 cm(-1). The differences in the molecular structure of the two minerals are attributed to the Al/Fe ratio in the minerals.

Near-infrared spectroscopic study of [AlO4Al12(OH)23(H2O)12]7+-O-Si(OH)3 nitrate crystals formed by forced hydrolysis of Al3+ in the presence of TEOS.

The polymer [AlO4Al12(OH)23(H2O)12]7+-O-Si(OH)3 was prepared by forced hydrolysis of Al3+ up to an OH/Al molar ratio of 2.0 in the presence of monomeric orthosilicic acid. Crystalline material was obtained by slow evaporation. Although the near-infrared spectra of the Al13-sulfate and Al13-O-Si(OH)3 are very similar, there are differences related to the bonding of the -O-Si(OH)3 group to the Al13-unit. The strong complex of bands around 7000 cm(-1) associated with the overtones and combination bands of the OH-stretching modes for Al13-sulfate is much weaker for Al13-O-Si(OH)3 and the opposite is true for the complex of bands around 5000 cm(-1) associated with the water overtone and combination modes, suggesting that the outer OH-groups of the Al13-unit are involved in the formation of the new Al13-O-Si(OH)3 units. A weak band around 7370-7631 cm(-1) is interpreted as the overtone of the Si-OH stretching vibration around 3740 cm(-1). A low intensity band, absent for Al13-sulfate and -nitrate is observed around 5550-5570 cm(-1) and is interpreted as the overtone of the OH-stretching mode of the OH-groups in the vicinity of the central AlO4 in the Al13-unit around 2890-2935 cm(-1). The interaction between the -O-Si(OH)3 group and the Al13-unit has a small influence on other bands like the combination modes of water in the 4400-4800 cm(-1) region, which show a small shift towards higher wavenumbers. The internal OH-groups in the Al13-complex are relatively shielded by the water molecules and therefore do not reflect the influence of the -O-Si(OH)3 in their band positions.

Modification of kaolinite surfaces through mechanochemical treatment--a mid-IR and near-IR spectroscopic study.

The modification of kaolinite surfaces through mechanochemical treatment has been studied using a combination of mid-IR and near-IR spectroscopy. Kaolinite hydroxyls were lost after 10 h of grinding as evidenced by the decrease in intensity of the OH stretching vibrations at 3695 and 3619 cm(-1) and the deformation modes at 937 and 915 cm(-1). Concomitantly an increase in the hydroxyl-stretching vibrations of water is observed. The mechanochemical activation (dry grinding) causes destruction in the crystal structure of kaolinite by the rupture of the O-H, Al-OH, Al-O-Si and Si-O bonds. Evidence of this destruction may be followed using near-IR spectroscopy. Two intense bands are observed in the spectral region of the first overtone of the hydroxyl-stretching vibration at 7065 and 7163 cm(-1). These two bands decrease in intensity with mechanochemical treatment and two new bands are observed at 6842 and 6978 cm(-1) assigned to the first overtone of the hydroxyl-stretching band of water. Concomitantly the water combination bands observed at 5238 and 5161 cm(-1) increase in intensity with mechanochemical treatment. The destruction of the kaolinite surface may be also followed by the loss of intensity of the two hydroxyl combination bands at 4526 and 4623 cm(-1). Infrared spectroscopy shows that the kaolinite surface has been modified by the removal of the kaolinite hydroxyls and their replacement with water adsorbed on the kaolinite surface. NIR spectroscopy enables the determination of the optimum time for grinding of the kaolinite. Further NIR allows the possibility of continual on-line analysis of the mechanochemical treatment of kaolinite.

The behavior of hydroxyl units of synthetic goethite and its dehydroxylated product hematite.

The behavior of the hydroxyl units of synthetic goethite and its dehydroxylated product hematite was characterized using a combination of Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) during the thermal transformation over a temperature range of 180-270 degrees C. Hematite was detected at temperatures above 200 degrees C by XRD while goethite was not observed above 230 degrees C. Five intense OH vibrations at 3212-3194, 1687-1674, 1643-1640, 888-884 and 800-798 cm(-1), and a H2O vibration at 3450-3445 cm(-1) were observed for goethite. The intensity of hydroxyl stretching and bending vibrations decreased with the extent of dehydroxylation of goethite. Infrared absorption bands clearly show the phase transformation between goethite and hematite: in particular. the migration of excess hydroxyl units from goethite to hematite. Two bands at 536-533 and 454-452 cm(-1) are the low wavenumber vibrations of Fe-O in the hematite structure. Band component analysis data of FTIR spectra support the fact that the hydroxyl units mainly affect the a plane in goethite and the equivalent c plane in hematite.

Far-infrared spectroscopy of alumina phases.

Far-infrared spectroscopy (FIR) has been used to distinguish alumina phases boehmite, diaspore, gibbsite and bayerite. The pellets of samples were prepared by mixing alumina phases with polyethylene at a ratio of 1:50, and the spectra were recorded between 50 and 400 cm(-1). The spectrum of boehmite resembles that of diaspore in the 300-400 cm(-1) region. Boehmite has two characteristic FIR bands at 366 and 323 cm(-1), while diaspore has five at 354, 331, 250, 199 and 158 cm(-1). The spectrum of gibbsite resembles that of bayerite in the 230-300 cm(-1) region. Gibbsite shows three characteristic FIR bands at 371, 279 and 246 cm(-1), whereas bayerite shows six at 383, 345, 326, 296, 252 and 62 cm(-1). The overlapping bands were resolved, and the spectra were manipulated appropriately using band analysis techniques. The FIR spectra are in harmony with the FT-Raman spectra. Far-infrared spectroscopy allows the study and differentiation of the stretching of AlO4 units to characterize these four alumina phases. Far-IR spectroscopy complements the mid-IR and near-IR for distinguishing alumina phases in bauxites.

Infrared spectroscopy of goethite dehydroxylation. II. Effect of aluminium substitution on the behaviour of hydroxyl units.

Dehydroxylation of goethite as affected by aluminium substitution was investigated using Fourier transform infrared spectroscopy (FT-IR) in conjunction with X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA). The band intensities of hydroxyl vibrations were indicative of the degree of dehydroxylation and the changes in band parameters due to aluminium substitution were observed. The effect of aluminium substitution on band parameters of FT-IR spectra of goethite and its partially and fully dehydroxylated products, the mixture of goethite/hematite and hematite, were interpreted. The results of this study have confirmed that aluminium substituted goethite is thermally more stable than non-substituted goethite and is in harmony with the results of XRD and DTGA. A larger amount of non-stoichiometric hydroxyl units is associated with a higher aluminium substitution. A shift to a higher wavenumber of bending and hydroxyl stretching vibrations is attributed to the effects of aluminium substitution associated with non-stoichiometric hydroxyl units on the a-b plane relative to the b-c plane of goethite. The results provide information for the characterisation of activated bauxite containing hematite and goethite.