Beta-delayed proton emission around N=50 and the rp-process

Detailed information on the decay modes of very proton-rich heavy nuclei is a prerequisite for p-process nucleosynthesis models. We have therefore measured β-delayed protons and γ-rays from mass-separated sources of ⁹⁶Ag, ⁹⁸Ag and ⁹⁸Cd, and obtained βp branching ratios of 3.7(9) × 10^{t ?2}, (1.1 _?0.4 ^+0.5 ) × 10^?5 and <2.5 × 10^?4, respectively. The consequences of the experimental data for rp-process calculations and the results from a statistical model are briefly discussed.     

Beta-delayed proton emission around N=50 and the rp-process

Detailed information on the decay modes of very proton-rich heavy nuclei is a prerequisite for p-process nucleosynthesis models. We have therefore measuredβ-delayed protons andγ-rays from mass-separated sources of⁹⁶Ag,⁹⁸Ag and⁹⁸Cd, and obtainedβp branching ratios of 3.7(9)×10^?2, (1.1 _?0.4 ^+0.5 )×10^?5 and <2.5×10^?4, respectively. The consequences of the experimental data for rpprocess calculations and the results from a statistical model are briefly discussed.     

Deformed relativistic mean-field calculations on nuclei near Z = 50 with FSUGold

The ground-state properties of Sn, Te, Xe, and Ba isotopes have been systematically investigated in the framework of the deformed relativistic mean-field theory with the new parameter set FSUGold. The results show that FSUGold is as successful as NL3 ^* in reproducing the ground-state binding energies of the nuclei. The calculated two-neutron separation energies, quadrupole deformations, and root-mean-square (rms) charge radii are in good agreement with the experimental data. The parameter set FSUGold can successfully describe the shell effect of the neutron magic number N = 82 . Detailed discussions on the binding energies, two-neutron separation energies, quadrupole deformations, rms charge radii and “binding energies” of the last neutrons are given.     

Coupling of a quasi-particle to the pairing vibrations

The intermediate coupling model of odd nuclei, where a nucleon is coupled to the surface vibration of an even system, has been successfully used in explaining various nuclear properties. In this paper, it is pointed out that a similar picture is applicable to improve the BCS approximation for seniority-one states in the pairing force model by considering coupling of a quasi-particle to the pairing normal modes. It is shown that this model is, in part, equivalent to the variational approach which takes the blocking effect into account. Several models are compared numerically.     

T = 0 versusT = 1 pairing in 0(36) limit of IBM-4 for heavyN = Z nuclei

In theO(36) limit of the interacting boson model including spin-isospin degrees of freedom (IBM-4), starting with a group chain that preservess andd boson spins and isospins together with a simple mixing hamiltonian, it is shown that the model generates, for heavyN =Z nuclei, even-even to odd-odd staggering in the number ofT = 0 pairs in the ground states for moderate difference in the basicT = 0 andT = 1s-boson pair energies; the staggering disappears when the energy difference is large.     

γ-Spectroscopy of 89 215 Ac126 and proton pairing inN=126 isotones

Theγ-decay of 5 excited states along the yrast line has been observed in²¹⁵Ac by inbeamγ-spectroscopy. Lifetimes andg-factors of 3 isomeric levels have been measured. The data show that pairing dominates the structure ofN=126 isotones.     

The influence of pairing correlations on the isospin symmetry breaking corrections of superallowed Fermi beta decays

Within the framework of quasi-particle random phase approximation, the isospin breaking correction of superallowed 0⁺ → 0⁺ beta decay and unitarity of Cabibbo-Kobayashi-Maskawa mixing matrix have been investigated. The broken isotopic symmetry of nuclear part of Hamiltonian has been restored by Pyatov’s method. The isospin symmetry breaking correction with pairing correlations has been compared with the previous results without pairing. The effect of pairing interactions has been examined for nine superallowed Fermi beta decays; their parent nuclei are ²⁶Al, ³⁴Cl, ³⁸K, ⁴²Sc, ⁴⁶V, ⁵⁰Mn, ⁵⁴Co, ⁶²Ga, ⁷⁴Rb.     

The role of isospin on the N=Z line

The role played by isospin in nuclear structure phenomena encountered on the N=Z line is discussed. New results on Coulomb energy differences (CED) at high spin for odd-A nuclei in the f _7/2 shell are presented and interpreted in the framework of a simple Cranked Shell Model treatment involving an exact numerical diagonalisation. Results for the CED between the A=46 even-even mirror pairs are also discussed. The CED between the T=1 states in N=Z odd-odd nuclei and their isobaric analogues are suggested as a possible probe of np pairing on the N=Z line. First results from a numerical diagonalization of IBM-4 are cited.     

QCD corrections to the forward-backward asymmetries of c and b quarks at the Z pole

Measurements of the forward-backward production asymmetry of heavy quarks in Z decays provide a precise determination of . The asymmetries are sensitive to QCD effects, in particular hard gluon radiation. In this paper QCD corrections for and are discussed. The interplay between the experimental techniques used to measure the asymmetries and the QCD effects is investigated using simulated events. A procedure to estimate the correction needed for experimental measurements is proposed, and some specific examples are given. Received: 26 February 1998 / Published online: 2 June 1998     

Study of the N = 50 major shell effect toward 78Ni at PARRNe⋆

The γ-ray de-excitations following the β-decay of ⁸³Ga and the β-n decay of ⁸⁴Ga have been studied. The radioactive species were produced using the PARRNe on-line mass-separator installed at the IPN Orsay Tandem accelerator. Two γ-lines were attributed to ⁸³Ge with the aid of β-γ and γ-γ coincidences. The Z identification of the γ-lines was provided by time analysis of a buid-up/decay cycle. The excited levels of ⁸³Ge can be explained by the coupling of the single neutron state ν2d _5/2 to the first 2⁺ excitation of the ⁸²Ge core.     

On the convergence of Marumori's boson expansion for pairing vibrations

It is demonstrated analytically for a two-level model with pairing force that Marumori's method converges rapidly if one uses the idea of pairing vibrations. The approximation of Sørensen and the broken-pair approximation are compared with Marumori's boson expansion.     

The effect of mechanical vibrations on holograms

The effect of mechanical vibrations on hologram recording is discussed, with emphasis on sinusoidal vibrations. A simple method for evaluating this effect is presented.     

Impurity effect on the phase transition at T = 0 in magnets. Critical oscillations in corrections to the scaling laws

Renormgroup equations are constructed for a magnet with impurities at T = 0. These equations are shown to possess a focus type stable point. The oscillations in the corrections to the scaling laws are a consequence of the focus.     

The effect of ultrasonic vibrations on heterogeneous catalysis

The effect of ultrasonic vibrations on vapour phase decomposition of cumene to benzene and propylene, was investigated employing a silica-alumina cracking catalyst. Ate temperatures and flow rates where external bulk diffusion controlled the rate of reaction, the application of ultrasound increased the mass transfer coefficient up to 40%. When surface reaction and internal pore diffusion controlled the speed of the reaction, the combined catalyst effectiveness factor — surface reaction rate constant was increased up to 160%.