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  • 1
    Electronic Resource
    Electronic Resource
    Spectroscopy and ultrafast dynamics of the 2A1 state of Z-hexatriene in gas phase (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 2205-2211 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: As in longer polyenes, the strong 1A1→1B2 band in the UV spectrum of 1,3Z,5-hexatriene (Z-hexatriene) has a weak precursor, the 1A1→2A1 transition. It was measured in this work by a conventional spectrometer. Whereas the wave number of the 0–0 transition is by 5400 cm−1 lower than that of the 1B2 origin, the vibrational contour indicates that the vertical transitions of thetwo bands nearly coincide. From the fast decay of the rotational anisotropy in the time-resolved measurements we conclude that this band is perpendicularly polarized. We measured the lifetime of the 2A1 state after pumping it directly by 250 fs pulses and probing the excited molecules by ionizing it by delayed pulses. The lifetimes decreased from several ps to 730 fs, when the excess energy was increased from near 0 to 4000 cm−1 and more. From the temperature dependence we infer a barrier of about 170 cm−1 (2 kJ/mol). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474080
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  • 2
    Electronic Resource
    Electronic Resource
    Femtosecond photochemical ring opening of 1,3-cyclohexadiene studied by time-resolved intense-field ionization (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 9386-9389 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We found that hydrogen ion formation due to multielectron dissociative ionization by an intense-laser field is much less efficient with 1,3-cyclohexadiene than with its isomer 1,3Z,5-hexatriene (Z-HT). Moreover by suppressing the ionization barrier an intense-laser field ejects electrons most efficiently from molecular states of low ionization potential. After pumping 1,3-cyclohexadiene at 267 nm to its 1B2 state we probe the system by intense-laser field ionization with delayed 800 nm pulses. Monitoring of the parent ion C6H8+, of the main fragment C6H7+ and of H+ allows us to follow the motion from the 1B2 surface to the dark 2A1 state and from there towards the 2A1/1A1 conical intersection to the ground-state surface of the product. The measured 1B2 and 2A1 lifetimes are 43±3 and 77±7 fs, respectively, and the primary photoproduct cZc-HT is produced within 200 fs. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474009
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of a symmetric multivalent molecule containing four carbohydrate substituents (1995)
    Springer
    Monatshefte für Chemie 126 (1995), S. 923-931 
    Details
    ISSN: 1434-4475
    Keywords: Carbohydrates ; Dendrimers ; Spacer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Ausgehend von den Allyl- und Pent-4-enyl-β-D-glucopyranosiden4–7 können dieD-Glucosederivate8–15 dargestellt werden, welche am anomeren Zentrum unterschiedlich lange Spacereinheiten mit verschiedenen Endgruppen besitzen. Bei Reaktion von vier Äquivalenten des Caesiumsalzes von Propan-4-carboxy-1-yl-2,3,4,6-tetra-O-acetyl-β-D-glucopyranosid15 mit Pentaerythrityltetrabromid entsteht das tetravalente Molekül16.
    Notes: Summary Starting with allyl- and pent-4-enyl-β-D-glucopyranosides4–7, differentD-Glucose units (8–15) containing alkyl spacers of variable lenght and with different end groups can be prepared. Reaction of four equivalents of the caesium salt derived from propan-4-carboxy-1-yl-2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside15 with pentaerythrityltetrabromide yields the tetravalent molecule16.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811012
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  • 4
    Electronic Resource
    Electronic Resource
    Indium mediated allylation in carbohydrate chemistry: A convenient synthesis of 3-deoxy-D-arabino-2-heptulosonic acid (DAH) and 3-deoxy-D-arabino-2-heptulose (kamusol) (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 1045-1050 
    Details
    ISSN: 1434-4475
    Keywords: 3-Deoxy-D-arabino-2-heptulosonic acid ; 3-Deoxy-D-arabino-2-heptulose (Kamusol) ; Indium mediated allylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Eine kurzer und ökonomischer Syntheseweg für 3-Desoxy-D-arabino-2-heptulosonsäure (4) und 3-Desoxy-D-arabino-2-heptulose (Kamusol,8) wurde entwickelt. Im Schlüsselschritt der Synthesesequenz wurde die indiumunterstützte Allylierung vonD-Erythrose in wäßrigen Reaktionsmedien angewendet. Das mittels dieser Methode auf sieben Kohlenstoffatome verlängerte Kohlenhydrat-Grundgerüst konnte einfach in die Titelverbindungen übergeführt werden.
    Notes: Summary A short and economical synthesis of 3-deoxy-D-arabino-2-heptulosonic acid (4) and 3-deoxy-D-arabino-2-heptulose (kamusol,8) has been developed. In the key step of the reaction sequence, the indium mediated allylation ofD-erythrose in an aqueous solvent system was utilized generating a seven carbon backbone which was further transformed into the title compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807577
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  • 5
    Electronic Resource
    Electronic Resource
    Eine einfache Synthese aller vier stereoisomeren 2,2,5-Trimethyl-1,3-dioxolan-4-carbaldehyde (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 763-771 
    Details
    ISSN: 1434-4475
    Keywords: 2,2,5-Trimethyl-1,3-dioxolane-4-carbaldehydes ; aldopentose diethyl dithioacetals ; lead tetraacetate cleavage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and efficient procedure for the syntheses of all four stereoisomers of the 2,2,5-trimethyl-1,3-dioxolane-4-carbaldehydes1a–1d has been developed. Starting with readily available aldopentose diethyl dithioacetals2,6,10 and14, the title compounds were obtained by a selective protecting group strategy and subsequentRaney-nickel reduction, followed by lead tetraacetate cleavage. This procedure allows an application on a multigram scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01277638
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  • 6
    Electronic Resource
    Electronic Resource
    Fission probabilities of Cu, Nb, Ag, Ho, Au and Bi nuclei excited by stopped antiprotons (1995)
    Springer
    The European physical journal 352 (1995), S. 191-195 
    Details
    ISSN: 1434-601X
    Keywords: 25.85.W
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The A dependence of nuclear fission induced by stopped antiprotons has been measured. An unambiguous identification of the binary fission decay mode was provided by a coordinate measurement of complementary fission fragments in coincidence using a large-acceptance fission detector based on low pressure multiwire proportional chambers. A deep fissility minimum was observed nearA=100, in agreement with the general behaviour predicted by the liquid-drop model. An unexpectedly low and high fission probability was found for the Ag and Cu nuclei, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01298907
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  • 7
    Electronic Resource
    Electronic Resource
    Multiwavelength Q-switched CO2 laser with continuous discharge (1992)
    Springer
    Applied physics 55 (1992), S. 65-70 
    Details
    ISSN: 1432-0649
    Keywords: 42.60.Da ; 42.60.Fc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A low-pressure (20 mbar) CO2 laser allows to extract pulses at several selected wavelengths simultaneously from the same active medium. We demonstrated this, using an industrial laser modified by a Q-switch and a resonator with two branches. In one branch the wavelengths are spatially separated, whereas in the other they oscillate in one common transverse mode. We designed a multi-wavelength resonator which requires a single additional reflector compared to usual laser cavities. It provided tunable oscillation at six wavelength simultaneously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348616
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  • 8
    Electronic Resource
    Electronic Resource
    3W average power 4.3 μm CO2 laser (1991)
    Springer
    Optical and quantum electronics 23 (1991), S. 405-410 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A 3 W average power CO2 laser oscillating in the range of 4.3μm (10°1 to 10°O transition) is described. At the same time, the laser can emit 100 W in the sequence band 00°2 to 10°1 (10.6μm). It is based on a commercial system with continuous-wave discharge of 12 m length and a slow gas flow. It operates in the Q-switched mode at pulse repetition rates up to 15 kHz. The pulse peak power is 1 kW and the pulse duration is 200 ns. The deviation from the theoretical efficiency limit has been decreased by a factor 2.5 in our device, due to saturation of the pumping (sequence band) radiation. We predict an improvement by another factor of 5 (possible average power of 10 to 20 W), if one avoids the absorption in the discharge-free zones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00619613
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  • 9
    Electronic Resource
    Electronic Resource
    Scientific goals and experiments of the project “winter precipitation at Mount Rigi”: An overview (1993)
    Springer
    Water, air & soil pollution 68 (1993), S. 1-14 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Wet deposition plays an important role as a mechanism for cleansing of the polluted troposphere. Fluxes of pollutants from the atmosphere to earth's surface can affect soil and aquatic ecosystems. The investigation of the pollutant incorporation into wet deposition is therefore of considerable interest for environmental research. The project “Winter precipitation at Mount Rigi” addresses the processes determining the chemical composition of wet deposition through an integrated approach considering atmospheric physical and chemical processes and their complex interactions. The investigated topics include: aerosol and gas scavenging, atmospheric chemistry (cloud water chemistry), cloud physics and dynamics. The design of the experiment, using three ground based measuring stations at the northwestern slope of the mountain, and the conceptual ideas using case study investigations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00479389
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  • 10
    Electronic Resource
    Electronic Resource
    Isotope selective dissociation of CHClF2 by a one- and two-wavelengthQ-switched CO2 laser (1992)
    Springer
    The European physical journal 24 (1992), S. 47-56 
    Details
    ISSN: 1434-6079
    Keywords: 82.50. − m
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 13C isotope separation by multiphoton dissociation of CHClF2 was studied by a continuous-discharge CO2 laserQ-switched at 8 kHz. This laser can easily emit two or more wavelengths with good spatial and temporal overlap. The best irradiation results were obtained by the line pair 9P16 + 9P28. After optimizing also the pressures of CHClF2 and of buffer gases (He and Ar), the energy density and the gas speed, the process is now much less nonlinear than in previous experiments with a single wavelength. Differences to the TEA laser induced process were observed, and generally the pressure influence on yield and selectivity showed a variety of phenomena. They were interpreted in terms of collisional changes of spectra during the laser pulse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01436603
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