Centrifugal stretching from lifetime measurements in the 170Hf ground state band

Centrifugal stretching in the deformed rare-earth nucleus 170Hf is investigated using high-precision lifetime measurements, performed with the New Yale Plunger Device at Wright Nuclear Structure Laboratory, Yale University. Excited states were populated in the fusion-evaporation reaction 124Sn(50Ti,4n)170Hf at a beam energy of 195 MeV. Recoil distance doppler shift data were recorded for the ground state band through the J=16+ level. The measured B(E2) values and transition quadrupole moments improve on existing data and show increasing β deformation in the ground state band of 170Hf. The results are compared to descriptions by a rigid rotor and by the confined β-soft rotor model. © 2013 American Physical Society

Low-energy structure of the even-A 96−104 Ru isotopes via g-factor measurements

The transient-field-perturbed angular correlation technique was used with Coulomb excitation in inverse kinematics to perform a systematic measurement of the g factors of the first excited 21+ states in the stable even-A isotopes Ru96-104. The measurements have been made relative to one another under matched kinematic conditions and include a measurement of g(21+)=+0.47(3) in Ru96

Capture cross sections from (p,d) reactions

Cross sections for compound-nuclear reactions involving unstable targets are important for many applications, but can often not be measured directly. Several indirect methods have been proposed to determine neutron capture cross sections for unstable isotopes. We consider an approach that aims at constraining statistical calculations of capture cross sections with data obtained from light-ion transfer reactions such as (p,d). We discuss the theoretical descriptions that have to be developed in order to extract meaningful cross section constraints from such data and show some benchmark results

Spin dependence of critical point behavior for first and second order phase transitions in nuclei

A study of first and second order nuclear shape phase transitional behavior in yrast states of even-even nuclei in the context of the Interacting Boson Model-1 is presented. Finite boson number effects are identified using calculations with up to 150 bosons, and the role of the rotational degree of freedom of observables in first and second order quantum phase transitional nuclei is discussed. We aim to provide a first investigation of the angular momentum dependence of experimentally accessible phase transitional signatures in finite-sized quantum nuclear systems. � 2008 The American Physical Society

Scaling properties of quantum shape phase transitions in the interacting boson model-1

The evolution of system observables at critical points of quantum phase transitions in atomic nuclei is explored within the context of the interacting boson model-1. The evolution of energies and transition strengths in the ground state band at the infinite-size critical point are examined with respect to system size. Properties of first-order phase transitions away from the U(5)-SU(3) leg of the Casten triangle are examined, and the effects of angular momentum on the evolution of system observables at the critical point are investigated for the first time. � 2010 The American Physical Society

Effective critical points in finite quantum phase transitional systems

Properties of quantum phase transitional systems in atomic nuclei are explored within the context of the interacting boson model 1 for both first and second order systems. A traditionally experimental approach is used to search for the effective finite-size critical point as a function of system size and angular momentum by studying derivatives of observables across the phase transition region. The effects of angular momentum on quantum phase transitions are investigated, and properties of first order phase transitions within the Casten triangle are examined. � 2010 The American Physical Society

New signature of a first order phase transition at the O(6) limit of the IBM

Shape invariants within the interacting boson model are used to describe the ? deformation of the ground state and 02+ state along the ?-rigid leg of the extended Casten triangle between the symmetry limits SU(3) and SU(3)? via the O(6) limit. Similarly to the recently discovered ?-deformation crossing of the ground state with the 02+ state between the symmetry limits U(5) and SU(3), a crossing of those states with respect to the ? deformation is observed between SU(3) and SU(3)?. The newly introduced order parameter K3(01+)-K3(02+) shows a peaking behavior at O(6), which is a signature of a first-order phase transition and is observed at O(6) for the first time. Comparison with existing data and experimental prospects for measuring this signature are presented and differences and similarities between spherical-deformed and prolate-oblate first-order phase transitions are discussed. � 2010 The American Physical Society

Neutron response of the TLYC scintillator

The response of the recently developed Tl2LiYCl6(Ce) scintillator to neutrons was measured and the 35Cl(n,p) channel observed in the material for the first time. The scintillator was exposed to a 252Cf source mounted within a parallel-plate avalanche counter for fission-fragment coincident measurements. Proton- and t+α-like events are selected with the pulse-shape discrimination technique. Comparison of energy-deposition and time-of-flight allows the quenching of the different channels to be assessed. The 6Li(n,t)α channel is found to have its energy quenched to 37(1)% relative to γ-ray detection, while the proton energy deposition spectrum is quenched to 60(1)%

Capture cross sections from (p,d) reactions

Cross sections for compound-nuclear reactions involving unstable targets are important for many applications, but can often not be measured directly. Several indirect methods have been proposed to determine neutron capture cross sections for unstable isotopes. We consider an approach that aims at constraining statistical calculations of capture cross sections with data obtained from light-ion transfer reactions such as (p,d). We discuss the theoretical descriptions that have to be developed in order to extract meaningful cross section constraints from such data and show some benchmark results