arXiv subjects

P. von Brentano

Publications and source records attributed to P. von Brentano.

23 records · Page 2Linked to original sources

arXiv1999

Quasi-Deuteron Configurations in odd-odd N=Z nuclei

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.

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arXiv1999

Transition Rates between Mixed Symmetry States: First Measurement in 94Mo

The nucleus 94Mo was investigated using a powerful combination of gamma-singles photon scattering experiments and gamma-gamma-coincidence studies following the beta-decay of 94mTc. The data survey short-lived J^pi=1+,2+ states and include branching ratios, E2/M1 mixing ratios, lifetimes, and transition strengths. The mixed-symmetry (MS) 1+ scissors mode and the 2+ MS state are identified from M1 strengths. A gamma transition between MS states was observed and its rate was measured. Nine M1 and E2 strengths involving MS states agree with the O(6) limit of the interacting boson model-2 using the proton boson E2 charge as the only free parameter.

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arXiv1999

Strong fragmentation of low-energy electromagnetic excitation strength in $^{117}$Sn

Results of nuclear resonance fluorescence experiments on $^{117}$Sn are reported. More than 50 $γ$ transitions with $E_γ < 4$ MeV were detected indicating a strong fragmentation of the electromagnetic excitation strength. For the first time microscopic calculations making use of a complete configuration space for low-lying states are performed in heavy odd-mass spherical nuclei. The theoretical predictions are in good agreement with the data. It is concluded that although the E1 transitions are the strongest ones also M1 and E2 decays contribute substantially to the observed spectra. In contrast to the neighboring even $^{116-124}$Sn, in $^{117}$Sn the $1^-$ component of the two-phonon $[2^+_1 \otimes 3^-_1]$ quintuplet built on top of the 1/2$^+$ ground state is proved to be strongly fragmented.

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arXiv1998

Spreading Width for Decay out of a Superdeformed Band

The attenuation factor F responsible for the decay out of a superdeformed (SD) band is calculated with the help of a statistical model. This factor is given by 1/F = (1 + Gamma(down) / Gamma(S)). Here, Gamma(S) is the width for the collective E2 transition within the superdeformed band, and Gamma(down) is the spreading width which describes the mixing between a state in the SD band and the normally deformed (ND) states of equal spin. The attenuation factor F is independent of the statistical E1 decay widths Gamma(N) of the ND states provided that the Gamma(N) are much larger than both Gamma(down) and Gamma(S). This condition is generically met. Previously measured values of F are used to determine Gamma(down).

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arXiv1998

Odd-spin yrast states as multiple quadrupole-phonon excitations

The wavefunctions of the lowest odd spin positive parity yrast states in the IBA are shown to be nearly pure multiple quadrupole-phonon excitations even outside the three dynamical symmetries. The empirical data for collective nuclei with 30 < Z < 80 confirm these predictions. The quadrupole-phonon purity of the 2^+_1 state can be measured from E2-branching ratios of the 3^+_1 state. These data show a high correlation to the 2^+_1 Q-phonon purity deduced from the E2-decay of 2^+ states.

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