R.V. Jolos

Shell model description of “mixed-symmetry” states in 94Mo

Abstract Shell model calculations have been performed for the nucleus 94 Mo. The calculated excitation energies and electromagnetic properties of low-lying states are in good agreement with the data, which include states with mixed-symmetry (MS) assignments in previous interacting boson model studies. In the shell model large isoscalar E2 matrix elements are found between states with MS assignments indicating that they form a class of states with similar proton-neutron symmetry.

Quasideuteron configurations in odd-oddN=Znuclei

The isovector M1 transitions between low-lying T=1 and T=0 states in odd-odd N=Z nuclei are analyzed. Simple analytical expressions for M1 transition strengths are derived within a single-j-shell approximation for both j=l+1/2 and j=l-1/2 cases. The large B(M1) values for the j=l+1/2 case are attributed to quasi-deuteron configurations. The B(M1) values for the j=l-1/2 case are found to be small due to partly cancellation of spin and orbital parts of the M1 matrix element.

Quasideuteron states with deformed core

Abstract The M1 transitions between low-lying T =1 and T =0 states in deformed odd–odd N = Z nuclei are analyzed in the frames of the rotor-plus-particle model. Using the representation of an explicit coupling of angular momenta we show that strong coupling of the quasideuteron configurations to the axially deformed core results in a distribution of the total 0 + →1 + strength among a few low-lying 1 + states. Simple analytical formulae for B(M1) values are derived. The realization of the M1 sum rule for the low-lying 1 + , T =0 states is indicated. The calculated B(M1) values are found to be in good agreement with experimental data and reveal specific features of collectivity in odd–odd N = Z nuclei.

The scissors mode and other magnetic and electric dipole excitations in the transitional nuclei 178,180Hf

Abstract Photon scattering experiments have been performed on the heavy deformed nuclei 178,180 Hf using an E γ K quantum numbers, dipole excitation strengths, and level widths, have been extracted from the scattering cross sections. From the measured level widths lifetimes of 67 levels can be deduced. The excitation strength of the scissors mode is discussed and extends the systematics from the neighboring rare earth nuclei. Besides the ΔK = 1 excitations other dipole excitations have been observed that are distinguished from the scissors mode states by their different decay behavior.

Shape invariants in the multiple “Q-excitation” scheme

Abstract Simple relations are derived within the IBA which express the ground state expectation values of various multiples of the quadrupole operator in terms of a few E2 transition probabilities connecting low-lying collective states. A comparison with the exact IBA results for boson numbers N = 6 and 12 reveals an accuracy better than 85% over the whole symmetry triangle. For the IBA parameters range physically important for the description of nuclear data the accuracy is better than 90%. Using these relations, the values of the cubic and fourth-order scalars and also the average value of the asymmetry parameter γ are determined for several nuclei.

Rotational spectra and parity splitting in nuclei with strong octupole correlations

Abstract A formula is suggested to describe the energies of positive- and negative-parity states belonging to the ground-state alternating-parity rotational bands in nuclei with significant octupole correlations. The agreement with experimental data is quite good for actinide nuclei. This formula corresponds to the parity splitting from a one-dimensional potential well. It leads to a common moment of inertia for both parities at least for low angular momenta. At high angular momenta a slight difference in the moments of inertia is found, which is presumably due to backbending.

Triaxial rotor plus particle description of negative-parity states in proton-odd Cs nuclides

Abstract Excitation energies and branching ratios in 125,127,129Cs from recent Stony Brook experiments are reproduced by triaxial-rotor-plus-particle calculations. In particular the signature splitting between favored and unfavored yrast states can be reproduced, allowing the γ deformation to be determined. A systematics of deformation parameters (ϵ, γ) is given and compared with values for the neighboring even-even and neutron-odd Xe and Ba nuclei. Core wave functions are discussed, and differences with respect to the neutron-odd Xe, Ba nuclei are examined.

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.

The γ-decay of single-particle states in 205Pb and 207Pb using an Euroball Cluster detector

Abstract Single-particle states in the odd lead isotopes 205 Pb and 207 Pb were investigated using an Euroball Cluster detector and five usual Ge detectors at the Osiris cube spectrometer of the Cologne FN-Tandem accelerator. The states were populated by the subCoulomb neutron stripping reaction ( d , pγ ) at 10 MeV. About 102 γ-transitions could be observed for the first time. The energy of most of the observed states could be determined to an accuracy of about 0.2 keV. The ground state wave function of 206 Pb could be determined to contain: 66(5) % ν3 p 1 2 −2 , 19(3) % ν2 f 5 2 −2 , 10(3) % ν3 p 3 2 −2 , and 2(1) % ν2 f 7 2 −2 .

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.