A. Schmidt

Experimental evidence for56Ni-core breaking from the low-spin structure of theN=Znucleus2958Cu29

Low-spin states in the odd-odd N=Z nucleus 58Cu were investigated with the 58Ni(p,n gamma)58Cu fusion evaporation reaction at the FN-tandem accelerator in Cologne. Seventeen low spin states below 3.6 MeV and 17 new transitions were observed. Ten multipole mixing ratios and 17 gamma-branching ratios were determined for the first time. New detailed spectroscopic information on the 2+,2 state, the Isobaric Analogue State (IAS) of the 2+,1,T=1 state of 58Ni, makes 58Cu the heaviest odd-odd N=Z nucleus with known B(E2;2+,T=1 --> 0+,T=1) value. The 4^+ state at 2.751 MeV, observed here for the first time, is identified as the IAS of the 4+,1,T=1 state in 58Ni. The new data are compared to full pf-shell model calculations with the novel GXPF1 residual interaction and to calculations within a pf5/2 configurational space with a residual surface delta interaction. The role of the 56Ni core excitations for the low-spin structure in 58Cu is discussed.

Approaching rotational collectivity in odd-odd NZ nuclei in pf-shell

Abstract The analysis of shell model wave functions and new experimental data for odd-odd Nue5fbZ nuclei 46V and 50Mn is presented in terms of collective rotor-plus-quasideuteron model. The low-lying low-spin states exhibiting collective properties appropriate for the K=0, K=3, and K=5 bands are identified. The strong isovector M1 transitions of quasideuteron origin in 46V and 50Mn are shown to be important indicators of collective features and to give more complete information on the structure of the intrinsic states than E2 matrix elements.

Low spin structure of odd-odd N=Z nuclei

Isovector M1 transitions between low-lying T=1 and T=0 states in odd-odd N=Z nuclei are discussed. Simple analytical expressions for M1 transition strengths are given in single-j-shell approximation. The large B(M1) values for the j = l + 12 case are attributed to quasi-deuteron configurations. The B(M1) values for the j = l − 12 case are found to be small due to a cancellation of spin and orbital parts of the M1 matrix element. The experimental data on low spin states in the odd-odd nuclei 54Co and 46V investigated with the 54Fe(p, nγ)54Co and 46Ti(p, nγ)46V fusion reactions at the EN-tandem accelerator in Cologne are reported. The Jπ = 01+, 21+, 41+ T=1 and Jπ = 11+, 31+, T=0 states in 54Co are identified as predominantly πf72−1 × νf72−1quasi-deuteron states.

Non-yrast low-spin states in the triaxially deformed nucleus 123Xe

Abstract The non-yrast states of 123 Xe have been investigated with the reaction 123 Te( 3 He,xa03n) by means of in-beam γ -spectroscopy using a setup of 6 Compton-suppressed high-purity-germanium (HPGe) detectors. More than 130 new transitions establishing over 35 new levels were observed. γγ angular correlations were analyzed to assign spins and parities to the low-lying states, and to determine the multipole mixing ratios of the γ -transitions. With this method 9 spin and parity assignments were made and 19 multipole mixing ratios could be determined. Excitation energies of negative-parity states and the branching ratios of their decays are compared with predictions of the Rigid Triaxial Rotor plus Particle model (RTRP).

Toward isovector M1 transitions in odd-odd N = Z nuclei

IsovectorM1 transitions between low-lying T=1 and T=0 states in odd-odd N = Z nuclei are discussed. The data on low-spin states in the odd-odd nuclei 46V and 50Mn investigated with the 46Ti(p, nγ)46V and 50Cr(p, nγ)50Mn fusion evaporation reactions at the FN-TANDEM accelerator in Cologne are reported. A simple explanation of the enhancement of the M1 transitions is given in terms of quasideuteron configurations. The fragmentation of the strong M1 transitions is shown to be due to the coupling of the two-particle configurations to the rotating core.