Mean lifetimes of the yrast {ital J}{sup {pi}}=16{sup +}{endash}26{sup +} states in {sup 130}Ce have been measured using the Doppler-shift-attenuation method in conjunction with the reaction {sup ...98}Mo({sup 36}S,4{ital n}){sup 130}Ce. A realistic computer simulation of the measured {gamma}-ray line shapes was used in the Doppler-shift-attenuation analysis for the slowing down of ions and description of delayed feeding cascades from yrast and side bands. The measured transition strengths are by a factor of 1.5 to 2 higher than reported previously. The results are compared with the microscopic calculations based on a realistic nucleon-nucleon interaction.
The concept of critical points in nuclear phase transitional regions is discussed from the standpoints of Q-invariants, simple observables and wave function entropy. It is shown that these critical ...points very closely coincide with the turning points of the discussed quantities, establishing the singular character of these points in nuclear phase transition regions between vibrational and rotational nuclei, with a finite number of particles.
Nuclear resonance fluorescence experiments have been performed on the deformed actinide nucleus {sup 236}U. Bremsstrahlung of 3.9 MeV endpoint energy has been used as the photon source. The scattered ...photons were detected by three high resolution Ge-{gamma}-spectrometers installed at scattering angles of 92{degree}, 128{degree}, and 150{degree}, respectively. Precise excitation energies, decay branching ratios, and ground state decay widths of numerous previously unknown spin 1 states in the excitation energy range 1.8--3.2 MeV have been extracted. The dipole strength has been found to be concentrated in the energy range 2.1--2.5 MeV. The systematics of the so-called {ital scissors} {ital mode} observed as a result of the previous ({gamma},{gamma}{prime}) and (e,e{prime}) experiments on {sup 232}Th and {sup 238}U and, in particular, their combined analysis suggests likewise to attribute these new dipole excitations in {sup 236}U to the orbital {ital M}1 scissors mode.
A method is developed to derive simple relations among the reduced matrix elements of the quadrupole operator between low-lying collective states. As an example, the fourth order scalars of Q are ...considered. The accuracy and validity of the proposed relations is checked for the ECQF Hamiltonian of the IBM-1 in the whole parameter space of the Casten triangle. Furthermore these relations are successfully tested for low-lying collective states in nuclei for which all relevant data is available.
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