Coupled-channel description of the photodisintegration of 24Mg, 28Si, and 32S nuclei within the intermediate-coupling scheme

The coupled-channel method is used to calculate photonuclear reactions on ²⁴Mg, ²⁸Si, and ³²S nuclei within the intermediate-coupling scheme. The origin of relatively narrow peaks corresponding to photoabsorption on these nuclei is studied. Partial channels of giant-dipole-resonance decay are considered. It is shown that the splitting of the giant dipole resonance in the ²⁴Mg nucleus into two broad maxima is due to the deformation of its surface.     

Semimicroscopic description of the gross structure of a giant dipole resonance in light nonmagic nuclei

A simple model is formulated that makes it possible to describe the configuration and deformation splittings of a giant dipole resonance in light nonmagic nuclei. The gross structure of the cross sections for photoabsorption on ¹²C, ²⁴Mg, and ²⁸Si nuclei is described on the basis of this model.     

On the decay of the photo resonance in 14N and 14C nuclei

The decay of the photo resonances in ¹⁴N and ¹⁴C nuclei is analyzed in terms of the shell model with intermediate coupling. Cross sections and branching ratios of nucleon channels are compared with experimental data. Successive decay branches are estimated.     

A detailed study of the 12C + 16O fusion reaction at Ecm = 19 to 24 MeV

Excitation functions of evaporation residues following the ¹²C + ¹⁶O reaction are investigated at E_cm = 19 to 24 MeV. At the resonances which have been previously identified in the ¹²C(¹⁶O, ⁸Be)²⁰Ne two-body channel, an order of magnitude larger resonance cross section is observed in the fusion channel than that in the two-body one and is shared among a few evaporation residues (²⁰Ne, ²³Na and ²⁴Mg). Here the resonance cross section is defined as the resonance part of the cross section on a resonance in an excitation function. It is found that for each resonance the relative intensity of the resonance cross sections of these residues is fairly well explained by assuming that they are coming from the decay of a compound nuclear resonance. It indiates that these intermediate resonances have a large probability to proceed to the formation of a more complicated configuration prior to its decay into exit channels. However, the resonant enhancement in the fusion channel is found to be weak at three energies (E_cm = 19.7, 22.0 and 22.6 MeV), where prominent resonant structures have been observed in inelastic channels. These distinct situations may be attributed to the magnitude of level density of the compound nucleus.     

Nonexponential <Superscript>125m</Superscript>Te radioactive decay

Nonexponential decay of isomeric ^125mTe nuclei having intermediate Mössbauer levels and surrounded by their own decay products is observed and studied. A collective decay model is suggested for the nuclear systems of this type.     

Second-order non-spherical quadrupole phonon effects in 2s1d shell nuclei

Selected nuclear structure and nuclear reaction information pertaining to the nuclei ²⁴Mg and ²⁶Mg indicate second-order non-spherical quadrupole phonon effects predicted by Faessler and Greiner's rotation-vibration coupling theory.     

A comparative study of the electric giant dipole resonance of 24−26Mg

The electric giant dipole resonance of ^24?26Mg has been explored up to 30 MeV excitation energy with bremsstrahlung. ΔE, E spectra of charged photo-particles and spectra of prompt deexcitation γ-rays from excited residual nuclear states were obtained at various bremsstrahlung endpoint energies. The ²⁵Mg(γ, p₀), (γ, d), ^24,25Mg(γ, α) differential cross sections as well as ^24?26Mg(γ, xγ′) integrated cross sections are presented. The results are discussed in terms of one-particle, one-hole excitations and isospin composition of giant resonance states. A comparison with calculations for ²⁴Mg gives poor agreement. Excitations from deeper shells were found in the giant dipole resonance of ²⁴Mg, but do not seem to be concentrated at higher energies. In ²⁵Mg, only weak excitations of this kind were found, and they are completely absent in ²⁶Mg.     

Collinear ternary cluster decay of hyperdeformed <Superscript>60</Superscript>Zn at high angular momentum

Binary and ternary cluster decay of ⁶⁰Zn compound nuclei at high angular momentum, formed in the ³⁶Ar + ²⁴Mg reaction at E _lab(³⁶Ar) = 195 MeV, has been measured in a unique kinematic coincidence setup consisting of two large area position sensitive (x, y) gas detector telescopes with Bragg-ionization chambers (BRS). The BRS provides the opportunity to measure the reaction angles in-and out-of-plane, and through Bragg-curve spectroscopy to achieve a complete identification of the nuclear charge for different final channels. We observed very narrow out-of-plane angular correlations for two heavy fragments emitted either in purely binary events or in events with a missing mass consisting of 2 and 3α particles. These narrow correlations are interpreted as ternary fission decay from compound nuclei at high angular momenta through an elongated (hyperdeformed) shape with a very large moment of inertia. In these stretched configurations, the lighter mass in the neck region remains at rest or with very low momentum in the center of mass. The text was submitted by the authors in English.     

Giant Gamow-Teller resonance in neutron-rich nuclei

The giant Gamow-Teller resonance and other branches of collective nuclear excitations are described on the basis of the theory of finite Fermi systems. A connection between the Gamow-Teller resonance and Wigner SU(4) symmetry is proven. The beta-decay strength function and processes accompanying the β ⁻ decay of neutron-rich nuclei are described. The effect of the satellites of the Gamow-Teller resonance on the decay properties of neutron-rich nuclei is analyzed.     

稳定和不稳定核巨共振性质的相对论研究

在相对论平均场的基态上自洽的相对论无规位相近似(RRPA)理论框架下,研究稳定核和不稳定核的巨共振性质.研究了稳定核²⁰⁸Pb,¹⁴⁴Sm,¹¹⁶Sn,⁹⁰Zr,⁴⁰Ca,¹⁶O和不稳定核Ca同位素链同位旋标量和同位旋矢量集体巨共振激发,并讨论了Dirac海负能核子态和矢量介子空间分量对核的巨共振性质的影响.研究的结果表明,Dirac海负能核子态和矢量介子空间分量对同位旋标量激发有贡献,特别是对重核,而对轻核它的贡献减弱,对于同位旋矢量激发的贡献可忽略.几组常用的相对论平均场非线性模型参量,不仅能成功的描述有限核的基态性质,也能很好地描述核的巨共振激发.对于N/Z极端情况下,同位旋矢量巨偶极激发模式存在低能集体激发,它是由于费密面附近弱束缚核子的激发和同位旋混杂效应 关键词： 相对论无规位相近似 核巨共振     

Giant monopole resonances in the statistical model

The strength functions fore ⁺ e ^– pair decay of the isoscalar and isovector giant monopole resonances in highly excited nuclei are derived and used in a statistical model calculation of thee ⁺ e ^– pair energy spectrum from compound nuclear decay in¹¹⁰Sn following a fusion evaporation reaction. This result is then compared to thee ⁺ e ^– spectrum derived from internal pair decay of the giant dipole and giant quadrupole resonances. The computation shows that the pair decay from the excited-state GDR dominates the pair spectrum over the region of all giant resonances, exceedingL=0 transitions by at least a factor of ten. We also compute the angular correlations betweene ⁺ ande ^– for theL=0, L=1 andL=2 transitions and estimate their power to discriminate between the various multipolarities.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

Refinement of the giant dipole resonance parameters with allowance for all exit channels of photonuclear reactions

The contribution from various channels of photonuclear reactions is considered to obtain parameters of the giant dipole resonance (GDR). It is pointed out that the channel with emission of charged particles is very important for some nuclei. GDR parameters for the ⁶⁰Ni, ⁶³Cu, and ⁶⁴Zn nuclei are evaluated with allowance for all exit channels of photonuclear reactions. The EMPIRE-II code is used for theoretical calculations.