Lifetime measurements of excited states in 162W and 164W and the evolution of collectivity in rare-earth nuclei

Lifetimes of the first excited
2
+
states in the extremely neutron-deficient
162
W
and
164
W
nuclei have been measured using the recoil distance Doppler shift technique. Experimental
B
(
E
2
)
data for the isotopic chains of hafnium, tungsten, and osmium, from the midshell region near the
β
-stability line towards the
N
=
82
closed shell and the most neutron-deficient nuclides, are compared with predictions of nuclear deformations and
2
1
+
→
0
g
.
s
.
+
reduced transition strengths from different classes of state-of-the-art theoretical model calculations. The results reveal striking differences and deficiencies in the predictive power of current nuclear structure models.