J. Metzinger

The quenching of low-energetic nuclear Gamow-Teller strength by δ-excitations

Abstract It is found in shell model calculations including ground state correlations, that δ-nucleon hole ( δ − h ) mixing affects the low-lying β − Gamow-Teller transitions much less than the Gamow-Teller giant resonance (GTGR). This can be understood in a simple perturbation treatment as a destructive interference of first and second order contributions. It is therefore not possible to describe the δ-quenching mechanism by a constant renormalization of the axial vector current.

Calculation of the antineutrino spectrum from thermal fission of 235U

The electron and antineutrino spectrum of the products of thermal fission of 235U have been calculated. The uncertainty in the shape of the spectra is <5% in the range 2.5 ⩽ E ⩽ 7.5 MeV, as a result of a microscopic calculation of the beta decay schemes of neutron-rich fission products. Calculations of this type should give, as in the case of 235U investigated here, for arbitrary reactor fuel compositions a reliable basis for the interpretation of reactor ν oscillation experiments.

Experimental test of the brink hypothesis

Abstract The energy dependence of the γ-ray strength function built on an excited state was determined using the 89 Y(p, γ) 90 Zr reaction. The results support the Brink hypothesis.

The Gamow-Teller strength distribution in 208Bi — a prove of the charge distribution in 208Pb?

Abstract Comparison of the calculated Gamow-Teller (GT) strength distribution in 208 Bi with the measured (p,n) spectrum suggests evidence for ground state correlations in 208 Pb, which also seem to be necessary for an understanding of the charge distribution of lead.

Investigation of high-spin states in 152,153Ho

Abstract The level structure of the nuclei 152,153 Ho has been studied by the 122 Sr ( 35 Cl , x n ) reaction. A double anti-Compton spectrometer was used as detection system. The level scheme of 153 Ho was extended to the region of the “M1-quasicontinuum”. For 152 Ho a level scheme is proposed for the first time. An isomeric state was identified and located at E x = 2872 keV. The results are discussed in the frame of the systematics found in this mass region. Effective moments of inertia are deduced.

Giant dipole resonances built on excited states in 90Zr through radiative proton capture

Abstract We have studied the 89 Y(p, γ i ) 90 Zr reaction populating the states of 90 Zr at 0.0, 1.761, 2.186, 2.321 and 2.743 MeV. The 90° cross sections were measured from E p = 3.7 to 11.5 MeV. The data were analysed by the statistical and direct-semidirect models. Spectroscopic factors of low-lying states in 90 Zr were determined.

Beta Decay far from Stability and the Decay Heat of Nuclear Reactors

The interest in the β-decay properties of nuclides far (and not so far) from stability has increased in recent years. Since the calculation of the half-lives of neutron-rich nuclei published in [1], about 70 new isotopes have been discovered, and this number will increase rapidly with new experimental possibilities (see, e.g.[2–5]). The theoretical predictions [1] thus can be tested now on a rather large number of nuclei unknown at the time of the calculations. Fig. 1 compares the half-lives of the latter nuclides with the predictions of [1]. The theoretical values are found reliable within the expected limits. This is of importance in particular for the astrophysical conclusions on element synthesis, age of galaxy and more recently the value of the cosmological constant and the corresponding energy density of the vacuum [6–8]. The new data allow on the other hand to improve the calculations.

High Spin States Around A~150

The investigation of highly rotating nuclei in the mass region of A ≈ 150 through gamma spectroscopic methods offers a good possibility to study spin-induced nuclear shape changes at highest spins. In this transitional mass region [N ≈ 82–86, Z ≈ 62–68] between the doubly closed 62 146 Gd84 core at one end and the well-deformed nuclei on the other, Strutinsky-cranked shell model calculations predict for the even-even isotopes Sm, Dy, Er, etc., a shape change from spherical or slightly oblate deformation (γ = 60°, β ≈ 0.1) at low spins to superdeformed prolate (γ = 0°, β ≈ 0.6) or triaxial rotors in the spin region of J = 60 ℏ, as a function of proton and neutron number [1].

Direct-Semidirect Proton Capture in the GDR Region

Proton radiative capture excites the giant dipole resonance (GDR) predominantly through direct or semidirect processes. At excitation energies below the GDR region contributions from compound nucleus capture are expected to complicate this picture. The recent work of DOWELL et al. [1] has introduced a simple model, which finds the inverse photoproton strength integrated over the GDR to a good approximation proportional to the proton transfer spectroscopic factors.