Bibliothek

X
Sprache
Bevorzugter Suchindex
Ergebnisse pro Seite
Sortieren nach
Sortierung
Anzahl gespeicherter Suchen in der Suchhistorie
E-Mail-Adresse
Voreingestelltes Exportformat
Voreingestellte Zeichencodierung für Export
Anordnung der Filter
Maximale Anzahl angezeigter Filter
Autovervollständigung
Feed-Format
Anzahl der Ergebnisse pro Feed
Permalink Wenn Sie Einstellungen dauerhaft verwenden wollen, müssen Sie zuerst Ihre Einstellungen speichern und dann einen Bookmark auf den Permalink setzen
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 1
    Digitale Medien
    Digitale Medien
    Electro-optic response of chiral helicenes in isotropic media (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1301-1304 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Correlated quantum-chemical calculations are used to estimate the second-order electro-optic response of chiral helicene molecules in isotropic media. Dephasing-induced terms are included in a sum-over-states (SOS) perturbation formalism derived from the density-matrix expression. Besides the usual resonances associated with intrinsic electronic excitations of the material, resonant peaks are found at optical frequencies corresponding to energy differences between intermediate excited states. The mechanism for such resonance phenomena in helicenes is analyzed in the framework of a configuration interaction description of the singlet excited states. The possibility is discussed that in such a resonance regime the optical field can experience gain without linear loss. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.475501
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    Optical Absorption Spectra of Aromatic Isothianaphthene Oligomers: Theory and Experiment (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 3932-3938 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100012a011
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    Linear and nonlinear optical response of polyenes: A density matrix renormalization group study (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 2549-2555 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Using a symmetry adapted density matrix renormalization group (DMRG) formulation, we have calculated various optical spectra, including linear absorption, electroabsorption, third-harmonic generation, and two-photon absorption, for a series of linear polyene molecules (up to 40 carbon sites) modeled by an extended Hubbard–Peierls Hamiltonian within the intermediate correlation regime. The theoretical two-photon absorption spectrum for trans-octatetraene is in good agreement with experiment. By comparing the experimental linear absorption spectra and theoretical higher Ag state energies, it is suggested that the so-called cis-band actually corresponds to the threshold of the mAg band. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.476827
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 4
    Digitale Medien
    Digitale Medien
    Evolution of the third-order molecular polarizability in polyenes: A local view from atomic charge derivatives (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6163-6168 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The origin and chain length evolution of the static third-order polarizability, γ, are discussed in polyenes up to C80H82 via a local analysis of atomic π-orbital electric field-induced polarizations, i.e., of γ charges and their moments. This conceptually and computationally simple approach allows one to obtain a visual representation of the local contributions to γ. The patterns of these local contributions are observed to change qualitatively as a function of chain length; the end parts of the molecule dominate the third-order response at moderate chain lengths, while the contributions from the inner section are responsible for the slow chain-length saturation. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.477244
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 5
    Digitale Medien
    Digitale Medien
    On the nature of electronic excitations in poly(paraphenylenevinylene): A quantum-chemical investigation (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 2829-2841 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Correlated quantum-chemical calculations are performed on phenylenevinylene oligomers containing up to eleven repeat units, to characterize the nature of the electronic excitations relevant for the photophysical properties of the corresponding polymer. The focus is first on the nonlinear optical response of model conjugated chains and the simulation of their frequency-dependent (third-harmonic generation, electroabsorption, and two-photon absorption) response. From the assignment of the calculated resonance features, the excited states dominating the third-order nonlinear polarizability are identified and their chain-length dependence is investigated. On that basis, we build an essential-state single-chain model (that includes the 1Bu, 2Ag, mAg, and nBu states) and apply it to the interpretation of recent experimental data reported for poly(paraphenylenevinylene) and derivatives. We then examine how the exciton binding energy, here defined as the difference between the energies of the charge-separated nBu and the strongly optically allowed 1Bu excited states, is affected by both intrachain and interchain polarization effects. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.479560
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 6
    Digitale Medien
    Digitale Medien
    Electronic structure of molecular van der Waals complexes with benzene: Implications for the contrast in scanning tunneling microscopy of molecular adsorbates on graphite (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 99-105 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We investigate the electronic structure of molecular model systems in order to improve our understanding of the nature of the contrast, which is observed in the scanning tunneling microscopy (STM) imaging of organic adsorbates on graphite. The model systems consist of a benzene molecule, representing the substrate surface, interacting with various molecules representing alkyl chains, oxygen- and sulfur-containing groups, fluorinated species, and aromatic rings. We perform quantum-chemical calculations to determine the geometric structure, stability, and electronic structure of these molecular complexes and analyze the theoretical results in relation with experimental STM data obtained on monolayers physisorbed on graphite. It appears that the STM contrast can be correlated to the energy difference between the electronic levels of the substrate and those of the adsorbate. Finally, we observe that the introduction of a uniform electric field in the quantum-chemical modeling can enhance the electronic interaction between the partners in the complex. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.474356
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 7
    Digitale Medien
    Digitale Medien
    Ab initio study of the gas-phase structure and electronic properties of M–CH3 (M=Li, Na) and M–CCH (M=Li, Na, K): A combined post-Hartree–Fock and density functional theory study (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1178-1191 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The structure of isolated, monomeric M–CH3 (M=Li, Na) and M–CCH (M=Li, Na, K) has been recently determined by millimeter/submillimeter rotational spectroscopy. These accurate experimental results offer the opportunity for an extensive ab initio study of these molecules in order to assess the accuracy of the latest developments in density functional theory (DFT). As a general trend, DFT results from hybrid functionals (B1LYP, mPW1PW91, and PBE0) are in very good agreement with experiment while conventional functionals (BLYP) show slightly larger errors. In addition, DFT methods show rapid basis set convergence, whereas post-HF techniques [MP2, QCISD, and CCSD(T)] give comparably good results only using large basis sets. The properties derived from the electron density are computed to a fairly similar accuracy by all methods, provided a large basis set is used. The importance of a proper treatment of electron correlation in the description of the bond between the carbon and the alkali metal atom is emphasized. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.480671
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 8
    Digitale Medien
    Digitale Medien
    Nature of optical transitions in conjugated oligomers. II. Theoretical characterization of neutral and doped oligothiophenes (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 842-849 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The optical transitions in α-conjugated oligothiophenes are investigated on the basis of a theoretical approach, including correlation effects; the authors consider both the neutral and doped states. The results are able to provide a coherent interpretation of the sometimes contradictory experimental data. For the neutral oligomers, the authors report the evolution of the lowest energy, dipole-allowed triplet–triplet transition with increasing chain length. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.470065
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 9
    Digitale Medien
    Digitale Medien
    Two-photon absorption and third-harmonic generation of di-alkyl-amino-nitro-stilbene (DANS): A joint experimental and theoretical study (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 7834-7843 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The one- and two-photon optical absorption spectra as well as the frequency dependent third-harmonic generation response of a side-chain polymer containing 4-dialkylamino- 4′-nitro-stilbene (DANS) as its side group have been measured over a wide range of frequency. A three-state model, based on an intermediate neglect of differential overlap/multireference double-configuration interaction description of the excited states, provides a coherent picture of the dynamic response of DANS, but fails in reproducing the red shift observed when going from the linear to the nonlinear absorption spectra; including vibronic coupling within the Franck–Condon approximation improves the fit. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.470200
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 10
    Digitale Medien
    Digitale Medien
    Theoretical studies of the interaction between aluminum and poly(p-phenylenevinylene) and derivatives (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4357-4364 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We report the results of a theoretical study of the interaction between aluminum and poly(p-phenylenevinylene) and derivatives of poly(p-phenylenevinylene). This allows us to investigate the initial stages of formation of the metal/conjugated polymer interface. Applying the semiempirical Austin model 1 method, we find that aluminum reacts preferentially by forming covalent bonds with the vinylene linkages in both poly(p-phenylenevinylene) and poly(2,5-dimethoxy-p-phenylenevinylene). When carbonyl groups replace the methoxy groups, i.e., to form poly(2,5-dialdehyde-p-phenylenevinylene), new reactive sites are induced, leading to structures involving aluminum–oxygen bonds, with stabilities comparable to those involving reaction with the vinylene groups. In all of the three systems investigated, the interaction with aluminum induces major modifications of the polymer chains with interruptions of the π system caused by formation of sp3 sites. Charge distribution analysis indicates that electron charge transfer takes place from the aluminum atoms to the polymer chains.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.467486
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...