Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Raman spectrum and bonding of matrix isolated GeO2 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1782-1784 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A suitable experimental method for the synthesis of molecules like O=Ge=O, which cannot simply be generated by heating of the well known solids, is provided by matrix isolation technique. In solid noble or other inert gases Ge atoms react with O2. The formation of the CO2-like GeO2 species was monitored by IR spectroscopy some time ago. In order to determine the complete force field the Raman spectrum has now been recorded. Bonding in this species is discussed on the basis of experimental findings and ab initio calculations which have been performed in addition. These results reveal, that multiple bonding in the system GeO/GeO2 is completely different from that in the molecules CO and CO2. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480740
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    On the reactivity of NH formed from photoinduced decomposition of HN3 in an Ar matrix at 12 K toward N2 and CO: A combined matrix isolation and quantum chemical study (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 3321-3326 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Herein we report on the reactivity of NH produced from photolytically induced decomposition of HN3 in Ar matrices at 12 K. This reactivity was experimentally probed in matrix-isolation experiments and theoretically by detailed quantum chemical calculations. The mechanisms for reactions of HN with N2 and CO were examined. The results of the experiments show that triplet NH(3Σ) is formed as a detectable product of the photoinduced HN3 decomposition, indicating that the reaction of HN in its triplet electronic state with N2 to give HN3 (1A′) is opposed to a significant barrier. Using quantum chemical methods [coupled-cluster single double triple, complete active space self-consistent field, second-order Møller–Plesset] the barrier of this spin-forbidden reaction was estimated to be about 104–130 kJ mol−1 (depending on the level of theory), in good agreement with the results of earlier experimental and theoretical studies. On the other hand, our experiments show that HN(3Σ) reacts under matrix conditions with CO to give HNCO (1A′). The calculations show that the barrier for this reaction indeed is significantly lower (∼35 kJ mol−1) than the one for the reaction of HN(3Σ) with N2. Triplet–singlet conversion in both systems is achieved either through spin–orbit coupling or interaction with the "phonon-bath" of the Ar matrix environment. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492276
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Matrix isolation and spectroscopic characterization of a linear AlOSi radical (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1444-1448 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the past, matrix isolation technique proved to be a proper method to generate new species by oxidation and reduction of the high-temperature molecule SiO. In each case the variation of the SiO multiple bonding was of central interest. During the reduction of SiO with different metal atoms M, different MSiO intermediates result. The co-condensation of Al atoms with SiO ends up with a linear AlOSi radical, which represents the first example of a metal coordination via the O atom of SiO. The structural data based on IR- and Raman spectra are confirmed by quantum chemical calculations. Bonding of AlOSi is similar to that of the high-temperature molecule AlOAl; however, an additional electron is present in the lowest antibonding Π-orbital. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480710
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Raman-spectroscopy of oligomeric SiO species isolated in solid methane (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 7881-7887 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: From the IR-spectra of matrix isolated SiO species a D2h-structure has been postulated for the dimer and a D3h-structure for the trimer. High quality Raman-spectra—necessary for the complete characterization—were missing so far. Here we report the Raman-spectra especially of the totally symmetric vibrations for Si2O2 and Si3O3 and their 16O/18O isotopomers isolated in solid methane. We also detect the most intense A1-vibration of Si4O4 and can assign it with its 16O/18O isotopic splitting. Ab initio calculations for all oligomers are presented in order to support the assignment of the spectra and to obtain geometric and energetic information about the oligomeric species which have been detected experimentally. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480123
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Infrared spectrum of matrix isolated ClSiO and ab initio calculations (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 3769-3772 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Cl atoms and SiO molecules are trapped in a solid Ar matrix at 16 K. The formation of the as yet unknown ClSiO molecule has been followed via its IR spectrum. The stretching frequencies of the isotopic isomer 35Cl28Si16O are observed at 1160.9 and 509.4 cm−1. Experiments with the 18O isotopic isomers were performed in order to confirm the assignment of the absorptions and to characterize the force field. With the help of quantum chemical calculations (DFT) the optimized ClSiO bond angle is obtained at 125.2°. The computed bond lengths are determined to be 153.6 pm for d(Si–O) and 207.8 pm for d(Si–Cl). The SiCl bond is weak in comparison with that of Cl2SiO (203.4 pm) which is in line with a decrease in the corresponding Si–Cl force constant. The calculation of its thermodynamic data, ΔfH0(298)=−167.2 kJ/mol; ΔfS0(298)=+279.1 J/(mol⋅K), is of high importance for high temperature gas phase reactions of industrial processes, e.g., the combustion of SiCl4 by O2. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478267
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    An experimental evaluation of OCR text representations for learning document classifiers (1998)
    Springer
    International journal on document analysis and recognition 1 (1998), S. 116-122 
    Details
    ISSN: 1433-2825
    Keywords: Key words:Document classification – Feature selection – Learning – OCR –N-grams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. In the literature, many feature types are proposed for document classification. However, an extensive and systematic evaluation of the various approaches has not yet been done. In particular, evaluations on OCR documents are very rare. In this paper we investigate seven text representations based on n-grams and single words. We compare their effectiveness in classifying OCR texts and the corresponding correct ASCII texts in two domains: business letters and abstracts of technical reports. Our results indicate that the use of n-grams is an attractive technique which can even compare to techniques relying on a morphological analysis. This holds for OCR texts as well as for correct ASCII texts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100320050012
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The Detection of O=SiCl2 as an Intermediate During the Combustion Process of SiCl4 with O2 (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1531-1535 
    Details
    ISSN: 1434-1948
    Keywords: SiCl4 Combustion ; OSiCl2 ; Matrix isolation ; Thermodynamic data ; DFT calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During the technical important combustion of SiCl4 with oxygen [SiCl4(g) + O2(g) = SiO2(s) + 2·Cl2(g)] many intermediates have been detected in the past. However, the presence of the primary species O=SiCl2 has been discussed controversially until today. With the help of matrix isolation technique we have now been successful to monitor O=SiCl2 via its IR spectrum. With the help of quantum chemical calculations the thermodynamic data have been calculated first. On this basis it was possible to find the optimal conditions to trap OSiCl2 from the high-temperature equilibrium. Furthermore it could be shown via IR spectroscopy and quantum chemical calculations, that the radical OSiCl does not play a significant role within this combustion process.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 8
    Electronic Resource
    Electronic Resource
    As2(AlCp*)3  -  eine Verbindung mit polyedrischem As2Al3-GerüstDiese Arbeit wurde von der Deutschen Forschungsgemeinschaft und dem Fonds der Chemischen Industrie gefördert. Für hilfreiche Diskussionen bei den quantenchemischen Resultaten sind wir Dr. R. Köppe zu Dank verpflichtet. (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 108 (1996), S. 3003-3005 
    Details
    ISSN: 0044-8249
    Keywords: Aluminiumverbindungen ; Arsenverbindungen ; Cluster ; Heteropolyeder ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19961082328
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    [As2(AlCp*)3] - A Compound with a Polyhedral As2Al3 FrameworkThis work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. We thank Dr. R. Köppe for the helpful discussions on the quantum chemical results. (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 35 (1996), S. 2875-2877 
    Details
    ISSN: 0570-0833
    Keywords: aluminum compounds ; arsenic compounds ; clusters ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199628751
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...