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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 295 (1979), S. 241-247 
    ISSN: 1618-2650
    Keywords: Untersuchung von Schwefelverbindungen, aliphat ; Massenspektrometrie ; chem. Ionisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die wesentlichen qualitativen Eigenschaften der Massenspektren einer typischen Auswahl von aliphatischen Thiolen, Dithiolen, Sulfiden und Disulfiden nach chemischer Ionisation (CI) mit CH4 als Reaktantgas werden dargestellt. Die relativen Ionenintensitäten hängen stark ab von dem Probendruck in der CI-Kammer. Thiole bilden hauptsächlich die protonierte Molekel (M + 1), daneben beobachtet man als Besonderheit Ionen mit MZ 〉 M, die durch Anlagerung verschiedener Fragmente an (M) entstehen, sowie (2 M) and (2 M + 1). Dithiole spalten bevorzugt SH ab, weitere Ionen hoher Intensität sind (M), (M + 1) sowie Anlagerungsprodukte mit MZ 〉 M. Sulfide bilden neben dem im allgemein häufigsten Ion (M + 1) als gruppentypisches Ion das Diniere (2 M). Disulfide zeichnen sich aus durch einfache Spektren mit den vorherrschenden Ionen (M) und (3/2 M), einem Komplex der Zusammensetzung R3S3. t-Butylverbindungen haben aus sterischen Gründen kaum die Fähigkeit zur Komplexierung an der S-Funktion und neigen stärker zur Abspaltung von KW-Resten.
    Notes: Summary The essential qualitative features of the mass spectra of a representative set of aliphatic thiols, sulphides and disulphides after chemical ionization (CI) with CH4 as reactant gas are described. The relative intensities of the ions strongly depend on sample concentrations in the CI-box. Thiols preferably form the protonated molecule (M + 1), furthermore some fairly particular ions with mass number (MZ) greater than M are observed. These are formed via attachment of various fragments to M, as well as via dimerization (2M), (2M + H). Dithioles mainly release SH so the base ion is HSR. Other high intensity ions are (M), (M + 1) and addition products with MZ 〉 M. The base ion of sulphides is (M + 1), characteristic is the dimer (2M). Disulphides exhibit fairly simple spectra with mass (M) and (3/2 M) predominating. The latter is a complex R3S3. tert-Butyl-compounds do not tend to form cationic complexes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 301 (1980), S. 417-425 
    ISSN: 1618-2650
    Keywords: Analyse von Dimethyltrisulfid ; Massenspektrometrie ; Diskussion der Spektren
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary The mass spectra obtained by electron impact ionization (EI) of dimethyltrisulfide, both at constant sample pressure and during elution from a GC column, are essentially identical, with the molecular ion Me2S 3 + providing the basis peak. Masses heavier than the molecular ion are not observed. Chemical ionization, using nitrogen, methane or isobutane, gives rise to numerous ions of larger mass than that of the molecular ion. Particularly characteristic are sulfonium type structures Me3S n + , with n=3–6. In addition, radical cations of the type Me3SnCH 2 + and protonated trisulfide, Me2S3H+, are observed, even with N2 as ionizing gas, together with a variety of ions of lower hydrogen content. Further, a large number of ion types of lower mass than the parent molecule are formed. The mass distribution of ions in the spectrum is found to be highly dependent on the partial pressure of dimethyltrisulfide in the ion source. These phenomena were investigated and accounted for semiquantitatively.
    Notes: Zusammenfassung Dimethyltrisulfid liefert nach Elektronenstoßionisation bei konstantem Probendruck und bei GC-Probeneinlaß im wesentlichen identische Massenspektren. Das Molekülion Me2S 3 + stellt dabei den Basispeak dar. Größere Massen als die des Molekülions wurden nicht beobachtet. Bei chemischer Ionisation unter Verwendung von Stickstoff, Methan oder Isobutan als Reaktantgas entstehen zahlreiche Ionen mit höherer Masse als der des Molekülions. Charakteristisch sind hierbei sulfoniumartige Strukturen Me3S n + mit n=3–6. Daneben beobachtet man Radikalkationen des Typs Me2SnCH 2 + und protoniertes Trisulfid Me2S3H+ auch bei Ionisation mittels N2 sowie Ionenarten mit einem geringeren Wasserstoffgehalt. Weiterhin wird eine größere Anzahl von Ionenarten gebildet, deren Massen kleiner sind als die des Stammoleküls. Die Massenverteilung der Ionen im Spektrum hängt außerordentlich stark vom Partialdruck des Dimethyltrisulfids in der CI-Quelle ab. Diese Abhängigkeiten wurden semiquantitativ untersucht und dargestellt.
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  • 3
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2011-08-16
    Description: The laser-driven rocket in which remotely generated laser power is used to heat propellant belongs basically to the class of specific-impulse limited propulsion systems if difficult missions are considered. It was previously established that trip time reaches a minimum as specific impulse is varied for payload transfers from low earth orbit to synchronous orbit and return via laser-driven rocket propulsion, the computations being based on the perigee-propulsion laser drive described by Minovitch (1972). The present study shows that such minimum occur for all missions and that optimum specific impulse is primarily determined by the mission difficulty. More generally, this optimum specific impulse maximizes payload kinetic energy achievable with a fixed jet power and propulsion time. A formula relating propulsion time parameter to payload ratio is obtained for estimating mission capabilities of laser-driven rockets.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Journal of Spacecraft and Rockets; 12; Nov. 197
    Format: text
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  • 4
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-07-13
    Description: A space propulsion concept is proposed and analyzed which consists of a thin sheet coated on one side with fissionable material, so that nuclear power is converted directly into propulsive power. Thrust is available both from ejected fission fragments and from thermal radiation. Optimum thicknesses are determined for the active and substrate layers. This concept is shown to have potential mission capability (in terms of velocity increments) superior to that of all other advanced propulsion concepts for which performance estimates are available. A suitable spontaneously fissioning material such as Cf-254 could provide an extremely high-performance first stage beyond earth orbit. In contrast with some other advanced nuclear propulsion concepts, there is no minimum size below which this concept is infeasible.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-1042 , International Electric Propulsion Conference; Nov 14, 1976 - Nov 17, 1976; Key Biscayne, FL
    Format: text
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  • 5
    Publication Date: 2019-07-13
    Description: A space propulsion concept is proposed and analyzed which consists of a thin sheet coated on one side with fissionable material, so that nuclear power is converted directly into propulsive power. Thrust is available both from ejected fission fragments and from thermal radiation. Optimum thicknesses are determined for the active and substrate layers. This concept is shown to have potential mission capability (in terms of velocity increments) superior to that of all other advanced propulsion concepts for which performance estimates are available. A suitable spontaneously fissioning material such as Cf254 could provide an extremely high-performance first stage beyond earth orbit. In contrast with some other advanced nuclear propulsion concepts, there is no minimum size below which this concept is infeasible.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73469 , Intern. Electric Propulsion Conf.; Nov 14, 1976 - Nov 17, 1976; Key Biscayne, FL; United States
    Format: application/pdf
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