13 research outputs found
Level densities of nickel isotopes: microscopic theory versus experiment
We apply a spin-projection method to calculate microscopically the level
densities of a family of nickel isotopes Ni using the shell model
Monte Carlo approach in the complete shell. Accurate ground-state
energies of the odd-mass nickel isotopes, required for the determination of
excitation energies, are determined using the Green's function method recently
introduced to circumvent the odd particle-number sign problem. Our results are
in excellent agreement with recent measurements based on proton evaporation
spectra and with level counting data at low excitation energies. We also
compare our results with neutron resonance data, assuming equilibration of
parity and a spin-cutoff model for the spin distribution at the neutron binding
energy, and find good agreement with the exception of Ni.Comment: 5 pages, 3 figures, 2 tables, submitted to Phys. Rev. C, Rapid
Communication
Recent Advances in the Application of the Shell Model Monte Carlo Approach to Nuclei
The shell model Monte Carlo (SMMC) method is a powerful technique for
calculating the statistical and collective properties of nuclei in the presence
of correlations in model spaces that are many orders of magnitude larger than
those that can be treated by conventional diagonalization methods. We review
recent advances in the development and application of SMMC to mid-mass and
heavy nuclei.Comment: 6 pages, 5 figures, Proceedings of the Eleventh International Spring
Seminar on Nuclear Physic
High-precision excited state lifetime measurements in rare earth nuclei using LaBr3(Ce) detectors
To study how collective nuclear structure evolves towards mid-shell and test next-generation LaBr3(Ce) scintillation detectors, measurements of the lifetimes of 2+ 1 states in 168Hf and 174W were conducted at the Wright Nuclear Structure Laboratory. Prel
Evolution of collectivity near mid-shell from excited-state lifetime measurements in rare earth nuclei
The B(E2) excitation strength of the first excited 2+ state in even-even nuclei should directly correlate with the size of the valence space and maximize at mid-shell. A previously found saturation of B(E2) strengths in well-deformed rotors at mid-shell is tested through high-precision measurements of the lifetimes of the lowest-lying 2+ states of the Hf168 and W174 rare earth isotopes. Measurements were performed using fast LaBr3 scintillation detectors. Combined with the recently remeasured B(E2;2+1→0+1) values for Hf and W isotopes the new data remove discrepancies observed in the differentials of B(E2) values for these isotope
Excited State Lifetime Measurements in Rare Earth Nuclei with Fast Electronics
We investigated the collectivity of the lowest excited 2⁺ states of even-even rare earth nuclei. The B(E2) excitation strengths of these nuclei should directly correlate to the size of the valence space, and maximize at mid-shell. The previously identified saturation of B(E2) strength in well-deformed rotors at mid-shell is put to a high precision test in this series of measurements. Lifetimes of the 2⁺1 states in ¹⁶⁸Hf and ¹⁷⁴W have been measured using the newly developed LaBr₃ scintillation detectors. The excellent energy resolution in conjunction with superb time properties of the new material allows for reliable handling of background, which is a source of systematic error in such experiments. Preliminary lifetime values are obtained and discussed in the context of previous and ongoing work
High-precision excited state lifetime measurements in rare earth nuclei using LaBr3(Ce) detectors
To study how collective nuclear structure evolves towards mid-shell and test next-generation LaBr3(Ce) scintillation detectors, measurements of the lifetimes of 21+ states in 168Hf and 174W were conducted at the Wright Nuclear Structure Laboratory. Preliminary results indicate that the excellent time and energy resolution of LaBr3 detectors make them well suited to fast timing measurements, allowing for improved background subtraction and peak resolution in comparison to BaF2 detectors. Preliminary analysis shows an order of magnitude reduction in the statistical error of the 2+ lifetimes in comparison to literature values for both nuclei. In the case of 174W, a substantial reduction of the observed lifetime hints at the possibility of new physics in the region