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  • 1
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    Chemistry. Unraveling the molecular mechanisms of photoacidity (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-12-06
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Domcke, Wolfgang -- Sobolewski, Andrzej L -- New York, N.Y. -- Science. 2003 Dec 5;302(5651):1693-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Physical and Theoretical Chemistry, Technical University of Munich, 85747 Garching, Germany. domcke@ch.tum.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14657482" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Efficient deactivation of a model base pair via excited-state hydrogen transfer (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-12-04
    Description: We present experimental and theoretical evidence for an excited-state deactivation mechanism specific to hydrogen-bonded aromatic dimers, which may account, in part, for the photostability of the Watson-Crick base pairs in DNA. Femtosecond time-resolved mass spectroscopy of 2-aminopyridine clusters reveals an excited-state lifetime of 65 +/- 10 picoseconds for the near-planar hydrogen-bonded dimer, which is significantly shorter than the lifetime of either the monomer or the 3- and 4-membered nonplanar clusters. Ab initio calculations of reaction pathways and potential-energy profiles identify the mechanism of the enhanced excited-state decay of the dimer: Conical intersections connect the locally excited 1pipi* state and the electronic ground state with a 1pipi* charge-transfer state that is strongly stabilized by the transfer of a proton.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schultz, Thomas -- Samoylova, Elena -- Radloff, Wolfgang -- Hertel, Ingolf V -- Sobolewski, Andrzej L -- Domcke, Wolfgang -- New York, N.Y. -- Science. 2004 Dec 3;306(5702):1765-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max Born Institute Berlin, Max-Born-Strasse 2a, D-10247 Berlin, Germany. schultz@mbi-berlin.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15576616" target="_blank"〉PubMed〈/a〉
    Keywords: Aminopyridines/*chemistry ; *Base Pairing ; Chemistry, Physical ; DNA/*chemistry ; Dimerization ; Hydrogen/*chemistry ; Hydrogen Bonding ; Mass Spectrometry ; Models, Chemical ; Physicochemical Phenomena ; Protons ; Thermodynamics ; Ultraviolet Rays
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
    Electronic Resource
    Electronic Resource
    Resonances in molecular photoionization. III. Multichannel extension and application to polyatomic molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5571-5579 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Starting from a model Hamiltonian comprising an arbitrary number of discrete electronic configurations and an arbitrary number of electronic ionization continua as well as the vibrational degrees of freedom, a comprehensive theoretical description of near-threshold autoionization structure in molecular photoionization is developed. The discrete–continuum interaction is treated to infinite order and the infinite Rydberg series converging to the ionization thresholds are included as a whole in the treatment of the nuclear dynamics. The equivalence of the Feshbach projection-operator formulation and the multichannel-quantum-defect description is explicitly established in this rather general context. We derive a simplified model from the general formalism which is shown to reproduce naturally some recently observed features of vibronic autoionization via nontotally symmetric modes in polyatomic molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454568
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  • 4
    Electronic Resource
    Electronic Resource
    Resonances in molecular photoionization. IV. Theory of one-color and two-color near-threshold photoionization of molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6209-6219 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A relatively comprehensive theoretical description of one-color and two-color photoionization of molecules by strong laser fields is developed. The molecular system is modeled by a number of discrete electronic configurations and a number of electronic ionization continua in a diabatic representation, allowing for intramolecular coupling of the discrete states and the continua. The vibrational degrees of freedom are included in compact operator notation without invoking the Born–Oppenheimer approximation. The relevant radiative dipole couplings are treated nonperturbatively on an equal footing with the intramolecular couplings. The important Coulomb threshold effects (accumulating Rydberg series at the electronic–vibrational ionization thresholds) are included via a threshold expansion of the complex level-shift operators representing intramolecular and radiative couplings. The weak-field, long-time ionization rate (golden-rule formula) is rederived from the general theory both in the one-color and the two-color case. In the two-color case, strong-field effects caused by either one of the two lasers are briefly discussed. We derive a simplified multichannel-quantum-defect model from the general two-color formalism which nicely reproduces a number of characteristic features of vibronic autoionization recently observed in several polyatomic molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455438
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  • 5
    Electronic Resource
    Electronic Resource
    An approach to the "channel three'' phenomenon of benzene (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6433-6439 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The nonradiative decay of benzene excited within the S1 manifold is studied by assuming an open vibrational potential for the S2 state that leads to spontaneous breaking of hexagonal symmetry along a path for valence isomerization. The S2 state crosses the S1 electronic configuration (at the channel three threshold) as well as the ground state along the reaction path. The rate constants of nonradiative decay of the S1 state (in fact the S1uS2 internal conversion) and the S2 state (S2uS0 IC) are both quantum mechanically calculated by invoking microcanonical averaging over all vibrational levels accessible at a given excess of vibrational energy. The results obtained account for a number of features observed in spectroscopy of benzene at the channel three threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458959
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  • 6
    Electronic Resource
    Electronic Resource
    Resonances in molecular photoionization. I. Model calculations and analysis of general phenomena (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 176-187 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Near-threshold autoionization structure in molecular photoionization is described using the projection-operator formalism of scattering theory. We address ourselves to the common situation of a number of discrete valence states interacting with the ionization continuum and the Rydberg series converging to the ionization threshold. The infinite Rydberg series are included as a whole in the treatment of the nuclear dynamics. We consider, in particular, a simplified model (single valence state and harmonic potential energy curves) which allows a very simple, fast, and numerically stable evaluation of the photoionization cross section. Model calculations are performed for a wide range of parameters (shift of potential energy curves, coupling strengths, optical transitions moments). We discuss and analyze a variety of general features of autoionization structures in total and partial photoionization cross sections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452608
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  • 7
    Electronic Resource
    Electronic Resource
    Resonances in molecular photoionization. II. Autoionization effects in the NO molecule (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 331-338 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Near-threshold autoionization features in the photoionization spectroscopy of nitric oxide are studied by the use of the Feshbach projection-operator formalism of scattering theory. The complex autoionization structure in the photoionization spectrum of NO in the wavelength region of 1140–950 A(ring) is described by assuming one valence state interacting with the ionization continuum and the converging Rydberg series. The strong non-Condon effects observed in the photoelectron spectra of this molecule are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453632
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  • 8
    Electronic Resource
    Electronic Resource
    Ab initio investigation of potential-energy surfaces involved in the photophysics of benzene and pyrazine (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 5627-5641 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Potential-energy surfaces of the lowest singlet and triplet excited states of benzene and pyrazine have been calculated using complete-active-space self-consistent-field and multireference configuration interaction (MRCI) techniques. We have focused our attention on the saddle points and surface intersections associated with the reaction path to a biradical form called prefulvene. The barrier heights separating the prefulvenic minimum from the minimum of the planar aromatic form on the ππ* excited singlet surface and on the ground-state surface have been estimated by large-scale MRCI calculations. The conical intersection of the lowest ππ* excited singlet surface with the S0 surface has been mapped out in two dimensions, the reaction coordinate to prefulvene and the coordinate of maximum coupling perpendicular to it. The relevance of these ab initio potential-energy data for the interpretation of photophysical relaxation pathways in benzene and pyrazine ("channel-three'' effect) is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464907
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  • 9
    Electronic Resource
    Electronic Resource
    Ab initio characterization of the S1–S2 conical intersection in pyrazine and calculation of spectra (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 5298-5309 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Potential-energy functions of the three lowest singlet states of pyrazine have been computed on the self-consistent field, second-order Møller–Plesset (SCF/MP2) level as a function of ab initio determined ground-state normal coordinates. The electronic-structure calculations confirm the existence of a conical intersection of the S1(nπ*) and S2(ππ*) surfaces near the minimum of the latter surface. A vibronic-coupling model involving four spectroscopically active vibrational modes is constructed on the basis of the ab initio data. Absorption, resonance-Raman, fluorescence, and femtosecond time-resolved pump–probe spectra are computed for this model using previously developed methods. The results are compared with experimental data where available.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462715
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  • 10
    Electronic Resource
    Electronic Resource
    A problem of gauge for matter–radiation interaction in calculations of intensities of vibrational transitions (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 1133-1136 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theory of absolute intensities of molecular vibrational transitions is formulated in terms of the T matrix formalism of scattering theory. It is shown that the problem of the selection of the "velocity'' (A¯ ⋅ p¯) gauge or the "length'' (E¯ ⋅ r¯) gauge for description of the matter–radiation interaction in vibrational transitions is determined by the choice of the description of molecular eigenstates. The resulting consequences for radiationless transitions theory in polyatomic molecules are indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450554
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