G. Hlawatsch

Nuclear structure of 198Au studied with (n, γ) and (d, p) reactions and interpreted with the IBFFM

Abstract The 197 Au(d, p) 198 Au reaction was measured with the high-resolution Q3D spectrograph at the Munich Tandem Accelerator at θ lab = 35°, using 20 MeV deuterons. Average resonance neutron capture gamma rays were measured with a filtered neutron beam at the Brookhaven National Laboratory. Using also secondary (n, γ) data a level scheme of 198 Au was established with 66 levels up to an excitation energy of 1600 keV mostly with spin and parity assignments. The level energies, E2 and M1 branching ratios and (d, p) transfer data were compared with new model predictions of the interacting boson-fermion-fermion model (IBFFM). This model provides a basic understanding of 198 Au.

162Dy studied with (n, γ), (n, n′γ), (d, p) and (d, t) reactions

Abstract The γ-ray spectra of 162 Dy were measured by (n, γ), (n, γγ) and (n, n′γ) reactions. In the 161 Dy(d, p) and 163 Dy(d, t) reactions the levels up to 2600 keV and 3200 keV, respectively, were identified. The level scheme was extended by additional rotational states up to 2190 keV. The vibrational and two-quasiparticle states were described within the quasiparticle-phonon nuclear model.

Spectroscopy of 88Sr with the 87Sr(n, γ) and 87Sr(d, p) reactions☆

Abstract The γ-ray spectrum emitted after thermal neutron capture in 87 Sr was studied at the ILL high flux reactor with pair- and intrinsic Ge-spectrometers. 661 transitions were assigned to the reaction 87 Sr(n, γ) 88 Sr and 205 of them were placed into a 88 Sr level scheme of 47 levels. This represents 88% of the observed intensity. The level energies were determined with a precision of better than 20 ppm; the neutron binding energy was determined as 11 112.69 (22) keV. To aid the analysis high resolution particle spectra of the reaction 87 Sr(d, p) 88 Sr were measured at 20 MeV deuteron energy with the Munich Q3D spectrometer. 85 states were observed with this reaction. The data helped to establish newly found levels and to differentiate between primary and secondary transitions in the (n, γ) data. The observed level densities and primary transition strengths are compared with statistical model predictions and non-statistical effects are discussed.

Low-lying 128I excited states from the (n, γ) reaction

Abstract Gamma and conversion-electron spectra following the 127 I(n, γ) 128 I reaction have been studied with bent-crystal, magnetic, Ge(Li) and Si(Li) spectrometers in the range 20–600 keV. Gamma-gamma prompt and delayed coincidences in the range 25–600 keV have been investigated with the use of two Ge(Li) detectors. The 128 I level scheme involving 40 levels in the energy range 0–1000 keV has been constructed. Parity is determined for all the levels introduced. Unique spin values are assigned to 30 levels. The half-lives of the 133.611, 137.851 and 167.367 keV levels have been measured to be 12 ± 3, 845 ± 20 and 175 ± 15 ns, respectively. The 127 I(d, p) 128 I reaction has been investigated with 22 MeV deuterons at an angle of 30°. The 129 I(d, t) 128 I reaction has been studied with 15 MeV deuterons at an angle of 30°. The (n, γ) levels are found to match well with those from the (d, p), (d, t), (n res , γ primary ) and (p, n) reactions. A comparison of the (n, γ) levels with the (d, p) and (d, t) levels enabled the identification of the π g 7 2 ν S 1 2 , π g 7 2 ν d 3 2 , π g 7 2 ν h 11 2 , π d 5 2 ν S 1 2 , π d 5 2 ν d 3 2 and π d 5 2 ν h 11 2 two-quasiparticle multiplets. Energy splittings of these pn configurations by residual interactions taken as a combination of short-range Wigner, singlet and tensor forces have been calculated.

Structural and statistical aspects of extensive level schemes from (N,γ) and transfer reactions

The very precise spectrometers for (n,γ) and (n,e) reactions at the ILL, Grenoble, and the high resolution Q3D spectrograph at the Munich Tandem Accelerator yield very detailed information on nuclear transitions and excitations. These results allow the establishment of level schemes which are rather complete in a given spin and energy region and which contain frequently more than 70 levels with spin and parity information. Recently the nuclei 20F, 24Na, 28Al, 36Cl, 40K, 41K, 42K, 114Cd, 134Cs, 155Sm, 154Eu, 155Gd, 161Dy, 163Dy and several actinide nuclei have been investigated. The limits of this method and the possibilities to identify nuclear structures will be discussed. In particular the mixing of single particle and vibrational excitations in deformed nuclei will be treated. A statistical analysis of these extensive level schemes gives information on the level density, on the strength of gamma transitions and on gamma multiplicities of levels. A systematic survey of gamma multiplicities of low spin l...

Nuclear structure investigation with high resolution transfer reactions and n-capture results

The 197Au(d,p)198Au reaction was measured with the high resolution Q3D-spectrograph at the Munich tandem accelerator at Theta lab=35 degrees , using 20 MeV deuterons. An average resolution of 3 keV was achieved up to 1600 keV excitation energy. The level scheme of 198Au could thus be extended and compared with new model predictions. The 167Er(d,p)168Er reaction was measured at Theta lab=30 degrees with an average resolution of 3.5 keV using 15 MeV and 22 MeV deuterons. States between 0 and 2600 keV were populated and new levels were observed.