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The Infrared Spectrum of Comet Hele–Bopp as Seen by the Infrared Space Observatory (1997)

Leech, K. ; Crovisier, J. ; Bockelée-Morvan, D. ; [et al.]

Springer

Earth, moon and planets 78 (1997), S. 81-83

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ISSN: 1573-0794

Keywords: C/1995 O1 Hale-Bopp ; comets ; infrared spectroscopy ; ISO

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract Spectra of comet C/1995 O1 (Hale-Bopp) were obtained with the Infrared Space Observatory (ISO) at medium resolution with the grating spectrometer in the photometer (PHT-S) and/or at high resolution with the short wavelength spectrometer (SWS) and long wavelength spectrometer (LWS) in April 1996 (Crovisier et al., 1996), September–October 1996 (Crovisier et al., 1997a, b) and December 1997, at distances from the Sun of 4.6, 2.9 and 3.9 AU, respectively. For the first time, high-resolution spectra of a comet covering the entire 2.4 to 200 μm spectral range were obtained. The vibrational bands of H2O, CO2 and CO are detected in emission with PHT-S. Relative production rates of 100:22:70 are derived for H2O:CO2:CO at 3 AU pre-perihelion. H2O is observed at high spectral resolution in the ν3 group of bands around 2.7 μm and the ν2 group around 6 μm with SWS, and in several rotational lines in the 100–180 μm region with LWS. The high signal-to-noise ratio of the ν3 band observed on September–October 1996 allows accurate determinations of the water rotational temperature (28 K) and of its ortho-to-para ratio(2.45 ± 0.10, which significantly differs from the high temperature limit and corresponds to a spin temperature of 25 K). Longward of 6 μm the spectrum is dominated by dust thermal continuum emission, upon which broad emission features are superimposed. The wavelengths of the emission peaks correspond to those of Mg-rich crystalline olivine (forsterite). In the September–October 1996 spectra, emission features at 45 and 65 μm and possible absorption at 2.9–3.2 μm suggest that grains of water ice were present at 3 AU from the Sun. The observations made post-perihelion in late December 1997 led to the detections of H2O, CO2 and CO at 3.9 AU from the Sun (Figures 1 and 2). The production rates were ≈3.0 × 1028,3.5 × 1028 and ≈1.5 × 1029 s-1, respectively. This corresponds to H2O:CO2:CO = 100:110:500 and confirms that at such distances from the Sun, cometary activity is dominated by sublimation of CO and CO2 rather than by H2O.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1006283614308

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Pb2PdX6 (X = Cl, Br) - Verbindungen mit gestreckten [PdX6]-OktaedernProfessor Hanskarl Müller-Buschbaum zum 65. Geburtstage gewidmet (1996)

Duchâteau, M. ; Keller, H.-L.

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 622 (1996), S. 1231-1235

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ISSN: 0044-2313

Keywords: Dilead(II)-hexahalogenopalladate(II) ; crystal structure ; strongly elongated PdX6 octahedra ; DTA, IR/RAMAN, 207Pb MAS NMR ; Chemistry ; Inorganic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: Pb2PdX6 (X = Cl, Br) - Compounds with Elongated [PdX6] OctahedraIn contradiction to published data new compounds in the systems PbX2 - PdX2 (X = Cl, Br) with the formula Pb2PdCl6 (I) and Pb2PdBr6 (II) were found. These were synthesized by thermal treatment of the corresponding mixtures of PbX2 and PdX2 (X = Cl, Br). X-ray single crystal structure analysis shows isotypism of I and II, monoclinic, P21/c (No. 14), Z = 2, I: a = 9.037(2) Å, b = 6.224(1) Å, c = 8.162(1) Å, β = 90.31(7)β, II: a = 9.512(7) Å, b = 6.584(8) Å, c = 8.383(3) Å, β = 90.07(5)º. Strongly elongated PdX6 octahedra are found in the crystal structure. Additional characterisation of the compounds was done by DTA, IR/RAMAN spectra and 207Pb MAS NMR investigations. Remarcable low field shifts were found for 207Pb.

Notes: Entgegen Literaturangaben wurden in den Systemen PbX2 - PdX2 (X = Cl, Br) die neuen Verbindungen Pb2PdCl6(I) und Pb2PdBr6(II) aufgefunden. Sie wurden durch thermische Behandlung der binären Halogenide PbX2 und PdX2 im molaren Verhältnis 2:1 dargestellt (Einkristalle). Die Kristallstrukturen wurden mit Einkristallröntgenuntersuchungen ermittelt. I und II sind isotyp, monoklin, P21/c (Nr. 14), Z = 2, I: a = 9,037(2) Å, b = 6,224(1) Å, c = 8,162(1) Å, β = 90,31(7)º, II: a = 9,512(7) Å, b = 6,584(8) Å, c = 8,383(3) Å, β = 90,07(5)º. In Pb2PdX6 werden stark gestreckte PdX6-Oktaeder beobachtet. Die Verbindungen wurden außerdem mittels DTA, IR/RAMAN-Spektren und 207Pb-MAS-NMR-Untersuchungen charakterisiert. Für 207Pb wurde eine bemerkenswerte Tieffeldverschiebung beobachtet.

Additional Material: 5 Ill.