ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
    Approximately diabatic states: A relation between effective Hamiltonian techniques and explicit cancellation of the derivative coupling (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 545-551 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The identification of specific electronic structures that do not interchange with varying geometry is related to the problem of finding a set of approximately diabatic states. We propose a new transformation to identify such structures from one nuclear configuration to another one. This transformation, used in previously proposed schemes to construct nearly diabatic states, improves the efficiency of these procedures which can be related to the methods minimizing explicitly the nonadiabatic coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459554
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Fine vibrational structure in core-to-bound spectra of polyatomic molecules (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 5500-5514 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Near-edge x-ray-absorption fine-structure (NEXAFS) spectra of 1-butene (C4H8), acrylonitrile (C2H3CN) and 1,3-butadiene (C4H6) multilayers were recorded with high resolution (better than 100 meV at the carbon edge) and a theoretical method to interpret the vibrational structure of the observed C1s→π* bands is presented. The method is based on local (quadratic) approximations for the potential energy surfaces of both ground and excited electronic states, with input data obtained by ab initio calculations of normal modes for the ground state and energy gradients for the excited state within the framework of the equivalent core model. The method proved to be useful in qualitative terms, providing information on the nature of the excited modes and on the geometrical changes following the electronic excitation. We have also calculated the C1s→π* spectrum of ethylene (C2H4) and compared it to those obtained for C4H8, C2H3CN, and C4H6. Since the latter can be considered as substituted ethylenes, the validity of the building-block scheme for the vibrational splittings in inner-shell absorption spectra could be assessed by this comparison.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467339
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Ab initio near edge soft x-ray absorption fine structure (AI-NEXAFS) spectrum of ethylene (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 10537-10549 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present here an ab initio calculation of the C(1s−1,π*) absorption band of ethylene. The linear vibronic coupling model is used with the aid of large configuration interaction (CI) ab initio calculations. The vibronic model involves the three totally symmetric vibrational motions (ν1,ν2,ν3) and the two non-totally symmetric ones (ν11,ν12). For all these in-plane modes, the ab initio potential energy curves are obtained for the electronic ground state and for the two lowest core-excited (1s→π*) states by multireference CI calculations including variational and pertubative contributions. The potential curves are fitted by polynomial expansions from which two sets of effective parameters are extracted for the linear coupling model. In this way, through the effective parameters, anharmonicities of the potentials and changes in the frequency from the ground to the core-excited states are taken into account without any adjustment. The contribution of the out-of-plane modes (ν4,ν7,ν8) is also considered assuming the commutation of in-plane and out-of-plane Hamiltonians. The final calculated spectrum involving the in-plane and the out-of-plane vibrational modes is found to be in good agreement with the experimental one, showing evidence for symmetry breaking and core-hole localization. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480436
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Multistate vibronic coupling effects in the K-shell excitation spectrum of ethylene: Symmetry breaking and core-hole localization (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 4415-4429 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational fine structure of the prominent C1s-π* absorption band of ethylene and some of its isotopomers has been investigated theoretically with the aid of a specific (linear) vibronic coupling model. The presence of two equivalent C1s levels gives rise to two nearly degenerate electronic states of g and u symmetry, respectively, which can interact vibronically via the (planar) antisymmetric C–H stretching and bending modes (ν11 and ν12). In addition to these states of immediate interest, the present model comprises three more pairs of "effective" states at higher energy allowing one to describe the excitation of additional asymmetric (nonplanar) modes as a result of linear vibronic coupling. To a good approximation the intrapair vibronic coupling can be eliminated by using a representation in terms of localized C1s hole states. As a further result, the in-plane and out-of-plane modes become separable. The required vibronic coupling constants have been determined with the aid of ab initio calculations at various nuclear conformations using a second-order polarization propagator method. After slight readjustment of some of the parameters, the calculated spectral profiles are found to be in excellent agreement with the experimental findings. The theoretical spectra reflect strong excitation of nontotally symmetric modes (and the concomitant symmetry lowering), involving mainly the planar C–H stretching mode ν11 and the out-of-plane C–H bending mode ν8. While the planar distortion is a consequence of the equivalent core levels, the nonplanar symmetry lowering can be rationalized in chemical terms as a rehybridization effect in which the sp2 bonding scheme in the ethylene ground state is changed to sp3 in the excited state. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473488
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Nonradiative lifetimes for LiH in the A state using adiabatic and diabatic schemes (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 10515-10522 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Accurate positions and nonradiative lifetimes of states belonging to the adiabatic A state of LiH are estimated. The results coming from a Golden Rule treatment in the adiabatic scheme present excellent agreement with those obtained through a diabatic close coupling calculation. That confirms the accuracy reached in both approaches and also in the treatment of the diabatic–adiabatic transformation. It involves, in particular, an effective phase control that is needed to properly estimate nonadiabatic couplings. Also, a powerful numerical procedure to obtain energy profiles in the diabatic close coupling frame is described and applied in this work. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474215
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Ab initio adiabatic and diabatic potential-energy curves of the LiH molecule (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 1144-1156 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: For nearly all states below the ionic limit [i.e., Li(2s, 2p, 3s, 3p, 3d, 4s, and 4p)+H] we perform the first adiabatic and diabatic studies. This treatment involves a nonempirical pseudopotential for Li and a full configuration-interaction treatment of the valence-electron system. Core–valence correlation is taken into account according to a core-polarization-potential method. We present an analysis of the diabatic curves and introduce appropriate small corrections accounting for basis-set limitations. For the low-lying states, our vibrational level spacings and spectroscopic constants are in excellent agreement with the available experimental data and with the best all-electron results. Experimental suggestions are given for the higher states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463242
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Theoretical study of an unusual reactive collision Cs(7p)+H2→CsH+H. Diabatic approach of the collinear collision potential energy surfaces (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 4872-4881 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Cs(7p)+(X 1∑+g, v=0) H2→(X 2∑+, v=0) CsH+H reactive collision was recently experimentally observed from a crossed beam experiment by Crépin et al. This reaction is rather unusual since it starts from a highly excited state of the system (11th potential surface) and must reach the ground state surface in the product channel without energy loss. Accurate nonempirical CI calculations of the potential energy surface for the collinear collision are reported, using large basis sets and a nonempirical relativistic pseudopotential for the Cs atom. The adiabatic potential surfaces, which exhibit irregular behavior, are reinterpreted in terms of an ab initio nearly diabatic effective Hamiltonian spanned by five neutral repulsive channels Cs(6s)×H2, Cs(6p)×H2,..., Cs(7p)×H2 and an ionic very flat Cs+H−2 channel which tends to the product wave function (Cs+H−)×H. The intersection of these diabatic potential surfaces are accessible from the entrance energy and this picture supports a harpooning mechanism, the 7p electron jumping on the H2 system at RCsH ≈6 bohr, the reactive systems being those which remain diabatically on this ionic surface through the avoided crossings with the lower Cs(7s)×H2,...,Cs(6s)×H2 neutral surfaces. The electronic couplings between the diabatic states are given as functions of the RCsH and RHH coordinates and their behavior is qualitatively understood. The existence of accidental conical intersections between some neutral diabatic states and the ionic state potential surfaces is demonstrated; these conical intersections should increase the reaction cross section. This diabatic study confirms, therefore, the harpooning mechanism previously proposed to interpret this paradoxical photochemical reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450802
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Theoretical study of the visible photodissociation spectrum of Ar 3 + (1991)
    Springer
    The European physical journal 20 (1991), S. 25-28 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.d ; 31.70.Hq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The photodissociation of Ar 3 + is studied following a consistent theoretical approach from the Potential Energy Surfaces to the dynamics. Six P.E.S. are computed according to a D.I.M.-like model Hamiltonian. Transition dipole moments are determined using a similar method. The 4-D dynamics of this system is obtained with the H.W.D. method (Hemiquantal dynamic with the Whole DIM basis). All the 4 nuclear degrees of freedom and all the 6 electronic states are involved in the dynamical calculations, allowing for very general investigations. The main theoretical results are: 1 the spectrum essentially results from a Σ → Σg transition to the second excited electronic state along with a symmetric stretching motion 2 excited Ar 3 + molecules almost all dissociate in Ar+ + 2 Ar 3 dissociation in Ar 2 + + Ar requires special conditions such as low laser excitation and is predicted to increase with a specific excitation of the bending mode 4 the dominant symmetric stretching motion induces a bimodal kinetic energy distribution of the fragments. All these points are in close agreement with experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543929
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    facet.materialart.
    Unknown
    Vibronic coupling and core-hole localization inK-shell excitations of ethylene (1991)
    American Physical Society
    Details
    Publication Date: 1991-02-18
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 10
    facet.materialart.
    Unknown
    Sampling the Configuration Space of Finite Atomic Systems:  How Ergodic Is Molecular Dynamics? (2002)
    American Chemical Society
    Details
    Publication Date: 2002-04-01
    Print ISSN: 1089-5639
    Electronic ISSN: 1520-5215
    Topics: Chemistry and Pharmacology , Physics
    Published by American Chemical Society
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...