U. Mayerhofer

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.

Nuclear structure of 156Gd studied with (n, γ), (n, e−), (d, p), (d, t) reactions and lifetime measurements

Abstract The nucleus 156 Gd was studied with (n, γ) and (n, e − ) reactions at the Institut Laue-Langevin (ILL) in Grenoble. The (d, t) and (d, p) reactions were investigated at the Munich Tandem Accelerator. Primary gamma rays following average resonance capture were observed at the Institut for Nuclear Research in Kiev. Summed coincidences measurements were carried out at the Reactor IBR-30 in Dubna. An extensive level scheme was constructed up to 2.35 MeV including 413 transitions and 18 band assignments. Lifetimes of 16 selected levels were measured with the Gamma-Ray Induced Doppler broadening method at the ILL. Low-lying bands of positive and negative parity were interpreted in the framework of the spdf-IBA. The agreement was found to be quite good.

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.

The Q-value of the electron capture in 205Pb measured with transfer reactions

In order to determine the Q-value between 205Pb and 205Tl, the Q-values of the reactions 205Tl(d, t)204Tl, 206Pb(d , t)205Pb and 205Tl(3He, d)206Pb have been measured and found to be −1288.7(6) keV, −1831.2(5) keV and 1761.7(14) keV, respectively. The energies of these reactions were calibrated with the 158Gd(d, t)157Gd, 172Yb(d, t)171Yb, 184W(d, t)183W and 187Re(3He, d)188Os reactions. The decay energy of 205Pb was deduced to be 51.3(6) keV. This value is relevant for solar neutrino measurements.

The experimental structure of199Au and the interacting boson-fermion model

Gamma rays of199Au obtained after double neutron capture in197Au were measured at the ILL high flux reactor. A level scheme up to 1770 keV excitation energy is established. The result is compared with IBFM and Boson-Fermion-Symmetry calculations.

Electromagnetic transition strengths in the transitional doubly odd nucleus 198Au

Abstract The half-lives of low-lying levels in 198Au are determined by means of delayed coincidences and generalized controid-shift analysis in the (n, γ) reaction as follows: T 1 2 (3 + , 381.2 keV ) = 2.3(2), ns , T 1 2 (1 − , 192.9 keV ) = 0.7(2) ns , T 1 2 (1 − , 247.6 keV ) = 0.4(1) ns , T 1 2 (4 − , 215.0 keV ) = 0.4(2) ns . In some cases, decompositions of complex distributions were carried out in order to determine the corresponding time centroids. Upper limits are derived for the lifetimes of several other low-lying levels. The deduced electromagnetic transition probabilities B(σL) are compared to results of a new IBFFM calculation.

Level scheme of 194Ir

Abstract Levels of 194 Ir were studied using neutron capture and ( d , p ) reaction spectroscopy. A pair spectrometer was used to measure the high-energy γ-ray spectrum from thermal-neutron capture in an enriched 193 Ir target over the energy range 4640–6100 keV. From the same reaction, low-energy γ-radiation was studied using curved-crystal spectrometers, and conversion electrons were observed with magnetic spectrometers. Prompt and delayed γγ-coincidences were measured using semiconductor and scintillation detectors. Averaged resonance capture measurements were performed with 2 keV and 24 keV neutrons for primary transitions leading to excitation energies from 0 to 580 keV. Using 22 MeV deuterons, the 193 Ir( d , p ) high resolution spectra were observed with a magnetic spectrograph. The deduced nuclear level scheme of 194 Ir includes 38 levels connected by 184 transitions. Unambiguous spins and parities were determined for 25 levels. The rotor-plus-particle model was used for the interpretation of the level scheme assuming a strong mixing for Nilsson configurations having identical parities and K quantum numbers. IBFFM model calculations were performed and the obtained results were compared with the experimental level scheme.

High Resolution Spectroscopy Using Transfer Reactions

With a recently developed focal plane detector for the Q3D‐spectrograph at the Munich Tandem Accelerator the Q‐values of the reactions 205T1(d,t)204T1, 206Pb(d,t)205Pb and 205T1(3He,d)206Pb were measured. With this data the Q‐value of the 205T1(ec)206Pb reaction was determined to be 51.4(6) keV. In order to obtain more complete experimental data on 104Rh the 103Rh(d,p)104Rh, 106Pd(d,α)104Rh and 105Pd(d, 3He)104Rh reactions were measured. The odd‐odd nucleus 104Rh has many low lying energy levels because of the neutron‐proton coupling. In comparison with 103Rh(n,γ)104Rh data new energy levels were found and the angular momentum transfer was determined.

Nuclear Structure Investigations and Lifetime Measurement in 156Gd

The level structure of 156Gd has been studied using the neutron capture reaction at the ILL in Grenoble with the Gams 2/3 spectrometer and the pair spectrometer PN4. The conversion electron spectrum has been measured with BILL. Lifetimes have been measured using the GRID‐Method. ARC measurements have been carried out at the Institut for Nuclear Research in Kiev. The direct reactions 155Gd(d,p)156Gd and 155Gd(d,t)156Gd have been investigated at the Munich Tandem Accelerator.