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  • 21.40.+d  (2)
  • 97.60  (2)
  • 21.60.Cs  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Microscopic multichannel calculation of the molecular dipole degree of freedom in the18O nucleus (1989)
    Springer
    The European physical journal 334 (1989), S. 1-9 
    Details
    ISSN: 1434-601X
    Keywords: 21.60.Cs ; 21.60.Gx ; 23.20.-G
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract StrongB(E1) transitions have been recently observed between states in the18O nucleus which follow roughly the energy sequence of a dimolecular α+14C rotator. These findings have been interpreted by Gai et al. as evidence for a molecular dipole degree of freedom being present in the18O nucleus. However, this idea was contradicted by the results of a microscopic multichannel calculation performed by Descouvemont and Baye which was based on elastic α+14C and inelastic α+14C(2+) many-body cluster wave functions. We have improved this study by performing a microscopic multichannel calculation including additionally an+17O many-body fragmentation in order to enlarge our model space by those shell model components which dominate the structure of the (positive parity)18O ground state band. Like Descouvemont and Baye we find a positive parity α+14C molecular band in18O and, additionally, a rather strong collectivity in the lowest 1−, 3− and 5− states in18O. However, since the internal structure is different within these states, the calculated states should not be interpreted as a negative parity α+14C molecular band. In this perspective, the microscopic multichannel calculations do not support the hypothesis of a molecular dipole degree of freedom being present in the18O nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294382
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Pycnonuclear triple-alpha-fusion rate in hypernetted chain Approximation (1992)
    Springer
    The European physical journal 342 (1992), S. 133-140 
    Details
    ISSN: 1434-601X
    Keywords: 21.30 ; 67.20 ; 97.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied the helium plasma in the hypernetted-chain-Approximation considering both short-ranged internuclear and long-ranged Coulomb interactions. The optimal two-particle wave function has been determined in HNC/0 approximation. The two-particle distribution functions, which have been calculated in various orders of HNC/n approximations (n=0, 4, 5), are used to determine the pycnonuclear triple-alpha-fusion rate in the density regime 108 g/cm3≤ρ≤1010 g/cm3, in which the fusing of three alpha-particles to form a12C-nucleus plays an important role in the crust evolution of an accreting old neutron star. Our calculation supports the idea that the helium liquid undergoes a phase transition to stable8Be matter at densities slightly lower thanρ≈3×109 g/ cm3 as the plasma induced screening potential then becomes strong enough to bind the8Be ground state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01288460
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Distortion effects in light hypernuclei (1989)
    Springer
    The European physical journal 334 (1989), S. 221-230 
    Details
    ISSN: 1434-601X
    Keywords: 21.80.+a ; 21.40.+d ; 21.60.Gx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied the particle-bound levels in the hypernucleiΛ 3,4H,Λ 5He,Λ 8Li andΛ 8,9Be in the framework of the full microscopic Resonating Group Method (RGM). In a first step we have solved the respective nuclear many-body problem within the RGM. For each hypernucleus we have then performed a static calculation, in which the nuclear degrees of freedom were kept fixed, and a dynamical calculation in which nuclear degrees of freedom were allowed to vary. The differences between these two studies allowed us to investigate nuclear distortion effects caused by the presence of theΛ-particle. We find the nuclear distortion effects to be inverse proportional to the binding of the nuclear constituents. Thus, the strongest effects are observed forΛ 3H and forΛ 9Be. Our dynamical approach does not show the strong overbinding ofΛ 3H andΛ 9Be as reported in other cluster model studies. Our results for thep-shell hypernuclei agree reasonably well with those obtained in a semi-microscopic Orthogonal Condition Model (OCM) study which used the same effectiveΛN-interaction as employed in our calculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294223
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Path integral Monte Carlo calculations of4He and6Li (1985)
    Springer
    The European physical journal 321 (1985), S. 677-685 
    Details
    ISSN: 1434-601X
    Keywords: 2.60+y ; 21.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have performed Monte Carlo calculations to estimate the exact energies of model problems for4He and theL=0,1, and 2 states of6Li. Using a Feynman path-integral expression for the imaginary-time evolution operator, we recast the ground state energy as a sum over histories, which are then sampled stochastically. Use of a trial wave function dramatically improves the efficiency of the Monte Carlo method. For a state-independent Malfliet-Tjon potential, together with the Coulomb interaction, we find a ground state energy of −28.00+0.20 MeV for4He, and a degeneracy of theL=0,1, and 2 states in6Li at about −59.65+-0.50 MeV. Density distributions for these nuclei are also calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01432445
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    The triple-alpha-reaction at low temperatures (1986)
    Springer
    The European physical journal 324 (1986), S. 147-152 
    Details
    ISSN: 1434-601X
    Keywords: 97.10 ; 97.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied the triple-α-reaction at low temperatures which is of importance on accreting white dwarfs and neutron stars. Although we have improved a recent investigation of Nomoto, Thielemann and Miyaji on several points, we find a reaction rate for the relevant temperature range (T=107−108K) which is rather similar to the previous result. In particular, our improved study confirms that helium might be ignited on accreting white dwarfs at temperaturesT≦4.107 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01325126
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    Paper (German National Licenses)
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