Abstract
Lifetime measurements have been made in the ground-state band of the transitional nucleus Gd from coincidence recoil-distance Doppler-shift data. Gd nuclei were produced using the Cd (Ar, 22) reaction with a beam energy of 190 MeV. Reduced transition probabilities have been extracted from the lifetime data collected with the Köln plunger placed at the target position of the JUROGAM-II array. The values have been compared with predictions from X(5) critical-point calculations, which describe the phase transition between vibrational and axially symmetric nuclear shapes, as well as with IBM-1 calculations at the critical point. While the excitation energies in Gd are consistent with X(5) predictions, the large uncertainties associated with the measured values cannot preclude vibrational and rotational contributions to the low-lying structure of Gd. Although experimental knowledge for the low-lying and -vibrational bands in Gd is limited, potential-energy surface calculations suggest an increase in softness in the ground-state band. In order to more fully account for the effects of softness, the X(5) and IBM-1 calculations need to be extended to include the degree of freedom for Gd.
- Received 4 July 2011
DOI:https://doi.org/10.1103/PhysRevC.84.024314
©2011 American Physical Society