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
  • 1985-1989  (6)
  • 1989  (6)
Source
Material
Years
  • 1985-1989  (6)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Valence ionization and the electron affinities of the open and cyclic forms of Se3 and Te3 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3582-3588 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Se3 and Te3 exist as the S3 molecule in an open C2v and a closed D3h form with different electronic configurations but nearly the same total energy. The ionization spectra of Se3 and Te3 are calculated in both the C2v and D3h forms by many-body Green's function methods. The D3h forms behave quite regularly, but very strong correlation effects are found in the C2v forms. If a theory accurate to third order is used, satellite lines appear at the ionization threshold. If higher order terms are included the satellite lines at the ionization threshold experience a slight change in energy, but a considerable reduction of intensity. Se3 has a positive electron affinity in both the C2v and D3h forms (2B1, 2A'2, states), and Te3 appears to have two positive electron affinities (2B1, 2A1 for the C2v form and 2A2 and 2E' for the D3h form).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456890
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Symmetry breaking and symmetry restoring in ions of loosely bound systems (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7039-7047 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a theoretical analysis of the effects that lead to distortion or symmetry restoration of the nuclear configuration in ions of weakly bound molecular systems and clusters. The vibronic coupling mechanisms involved are reviewed and discussed in terms of simple and general models. Guided by a qualitative characterization of the wave function of a loosely bound system, we study the symmetry determining effects for such ions in terms of first order (Koopmans'), relaxation and correlation distortion energies associated with electron removal from the parent system. Our discussion suggests that the Koopmans' approximation can reasonably be expected to provide a qualitatively correct dependence of the ion energy on nuclear motion. Exceeding these expectations, it is found in numerical applications to the He+3 and He+4 ions that the relaxation and correlation energy changes accompanying symmetry breaking tend to cancel exactly. This implies, and we show in practice, that while insufficiently accurate correlation energy estimates may easily lead to incorrect geometries, the inexpensive Koopmans' approximation can often suffice to obtain the correct energy curvature along symmetry breaking coordinates. Further preliminary results for N3 and CO+2 suggest that these findings have a much wider applicability than anticipated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457321
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Gauge theory and quasidiabatic states in molecular physics (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7057-7062 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Following previous works [Moody et al., Phys. Rev. Lett. 56, 893 (1986) and Zygelman, Phys. Lett. A 125, 476 (1987)], we review in some detail the gauge theoretical form of the Born–Oppenheimer description of molecules. The derivative couplings which describe nonadiabatic effects play the role of gauge potentials. Applying the gauge theoretical formalism (well known in particle physics), we rederive a theorem concerning the nonexistence of strictly diabatic states. Further we propose the Lorentz gauge condition to define quasidiabatic states. We show that the recently proposed block diagonalization method to obtain quasidiabatic states leads automatically to the Lorentz gauge locally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457323
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Statistical fluctuations of decay rates (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3934-3947 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We introduce a general Hamiltonian describing two coupled subsystems, each having a finite zero-order decay probability. With use of simple statistical assumptions on the underlying states, we derive new probability distributions of individual decay rates. We analyze the cases of weak and intermediate to strong coupling, respectively. The resulting distributions often resemble a suitable χ2 distribution, but do not belong to that class of functions. An interpretation of decay rates in terms of a χ2 model thus may lead to wrong conclusions. As a concrete realization, we study a Hamiltonian describing the non-Born–Oppenheimer coupling of two electronic states via the nuclear motion. The model is applied to the calculation of absorption-type spectra of NO2 and C2H+4. We investigate statistical properties of energy levels, line intensities, and decay rates. For NO2, we find from all statistics a completely irregular behavior, consistent with random matrix predictions and demonstrating the strong mixing of zero-order states due to the nonadiabatic coupling. For C2H+4, all statistics exhibit characteristic deviations from the irregular limit that can be given a consistent interpretation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456825
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Doubly ionized states of ethylene: Auger spectrum, potential energy surfaces and nuclear dynamics (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1734-1753 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Theoretical investigations of the outer valence doubly ionized states of ethylene are presented using ab initio Green's function and configuration interaction methods. The vertical double ionization potentials computed by the Green's function method using the ADC(2) scheme are discussed in connection with the Auger spectrum of ethylene and found to reproduce the experimental spectrum quite accurately. Another main purpose of the present work is the investigation of the potential energy surfaces of selected states via ADC(2) and the study of the nuclear dynamics on them. It is shown that only the ground state of the dication is nonplanar with a torsional angle of 90°. The investigation of the topology of the surfaces reveals a low energy conical intersection of the dicationic ground and first excited states. The associated vibronic coupling problem turns out to include, additionally, the second excited state and thus, we encounter here a three-state problem. In the approximation of linear vibrational and vibronic coupling the static and dynamic aspects of the vibronic interaction are investigated by a model Hamiltonian comprising three nonseparable nondegenerate vibrational modes. The input data for the model are extracted from the ADC(2) results. With the aid of this Hamiltonian we have computed a hypothetical "sudden'' double ionization spectrum of ethylene whose complex structure is analyzed stepwise and by cuts through the pertinent adiabatic and diabatic surfaces. The analysis exhibits that the conical intersection of the two lower lying states dominates the vibronic dynamics and leads to strong vibronic mixing between them. This mixing is indirectly reinforced by the interaction between the intermediate and the upper states. As a consequence, strong nonadiabatic effects occur in the ethylene dication. Furthermore, two of the three surfaces involved in the conical intersection are also involved in a multidimensional avoided crossing. A more detailed analysis presented earlier has exhibited that the states belong to an interesting class where two potential energy surfaces are likely not to coincide although plenty of nuclear degrees of freedom exist, in principle, to allow for an intersection to occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457080
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Influence of internal degrees of freedom on the structure of one-dimensional systems (1989)
    Springer
    The European physical journal 74 (1989), S. 513-525 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The structure of one-dimensional systems with a half-filled band is discussed. In addition to lattice coordinates several intramonomer coordinates are considered. It is found that the system distorts and dimerizes (Peierls distortion). The distortions can be caused by lattice coordinates, by intramonomer coordinates or by both types of coordinates simultaneously. Thereby the various intramonomer degrees of freedom act cooperatively. The interplay between the intramonomer and lattice coordinates may induce new types of phase transitions with critical temperatures below the usual Peierls transition. Depending on the values of the effective matrix elements up to two of these new transitions may occur for a given system. The impact of these additional phase transitions on the specific heat, energy gap and lattice structure is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01311398
    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...