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
Filter
  • 2000-2004  (1)
  • 1990-1994  (2)
  • 1920-1924
  • Chemistry  (2)
  • PACS: 31.15Ar; 31.15Qg; 31.50+w  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Theoretical exploration of stationary and of ultrafast spectroscopy of small clusters (2000)
    Springer
    Applied physics 71 (2000), S. 343-349 
    Details
    ISSN: 1432-0649
    Keywords: PACS: 31.15Ar; 31.15Qg; 31.50+w
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Stationary spectra offer information on the interplay between the structures and the nature of electronic excitations reflecting bonding properties, as shown by comparing Sin with Agn (n=4-6) clusters. In order to study the dynamical properties, simulations and analysis of femtosecond (fs) time-resolved pump–probe or pump–dump signals have been carried out, which allows us to determine the timescales and the nature of configurational changes versus internal vibrational relaxation (IVR) in electronic ground or excited states. For this purpose we have developed a multi-state ab initio molecular dynamics (involving ground as well as adiabatic or non-adiabatic excited electronic states) on the timescale of the nuclear motion, using the time evolution of a thermal ensemble in the Wigner representation. The combination of ab initio quantum-chemical methods used for the molecular dynamics ‘on the fly’ and the Wigner-distribution approach for the description of the motion of the nuclei also allowed the accurate determination of pump–probe and pump–dump signals under temperature-dependent initial conditions. We use this novel combination of methods to investigate the dynamics in excited states of non-stoichiometric NanFn-1 clusters with a single excess electron. The timescales of the structural relaxation in excited states versus intramolecular vibrational relaxation processes have been determined, as illustrated for the example of Na4F3. This is the first study of the system with 15 degrees of freedom for which the dynamics in the excited states has been carried out without the precalculation of the energy surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006967
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Untersuchungen zur Bildung wasserlöslicher Cellulosephosphate durch homogene Acylierung im System Cellulose N2O4/DMF. 1. Mitt.: Problemstellung und Ergebnisse zur Acylierung mit POCl3 (1991)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 42 (1991), S. 213-217 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: After dissolution in the N2O4/DMF-system resulting in a partial substitution of OH-groups by nitrite ester groups, cellulose has been phosphorylated at homogeneous conditions of reaction with POCl3 to DSp-values up to about 1 in the presence of triethylamine. Solubility of the products in water was found in the DSp-range between 0.3 and 0.6 after suitable treatment of the reaction product in a protic medium.
    Notes: Nach Auflösung in einem N2O4/DMF-Gemisch unter partieller Bildung des Nitritesters wurde Cellulose unter homogenen Reaktionsbedingungen mit POCl3 in Gegenwart von Triethylamin bis zu DSp-Werten von etwa 1 phosphoryliert. Wasserlösliche Produkte wurden im DSp-Bereich zwischen 0,3 und 0,6 nach einer Behandlung des Reaktionsproduktes in einem protischen Medium erhalten.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1991.010420506
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Untersuchungen zur Bildung wasserlöslicher Cellulosephosphate durch homogene Acylierung im System Cellulose/N2O4/DMF. 2. Mitt.: Ergebnisse zur Acylierung mit Derivaten des POCl3 und zusamenfassende Diskussion zum Ablauf der Phosphorylierung im System N2O4/DMF/Cellulose1. Mitt.: siehe [1] (1991)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 42 (1991), S. 554-560 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Cellulose and carboxymethyl cellulose are phosphorylated after dissolution in the N2O4/DMF-system by employing a modified acylation agent prepared by reaction of POCl3 with H2O and with N2O4, respectively. The N2O4-modified reagent was found to be suitable for preparing water-soluble cellulsoe phosphates in the Na+ and the triethylammonium salt form in a DS-range between 0.2 and 1.3. A reaction mechanism taking into account the steps of acylation and after-treatment is discussed.
    Notes: Cellulose und Carboxymethylcellulose wurden nach Auflösung im N2O4/DMF-System mit modifizierten Phosphorylierungs-reagentien acyliert, die durch Umsetzung von POCl3 mit Wasser oder mit N2O4 erhalten wurden. Das durch Umsetzung mit N2O4 modifizierte Reagens erwies sich als geeignet zur Gewinnung wasserlöslicher Cellulosephosphate in Form des Natrium-oder des Triethylammoniumsalzes im DS-Bereich zwischen 0,2 und 1,3. Ein Reaktionsmechnaismus für die bei Acylierung und Nachbehandlung ablaufenden Umsetzungen wird diskutiert.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1991.010421105
    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...