Excited superdeformed Kπ=0+ rotational bands in β-vibrational fission resonances of 240Pu

The intermediate structure of fission resonances of Pu-240 was observed with an experimental energy resolution of 7 keV in the excitation energy region of E* = 3.8-5.6 MeV using the Pu-239(d,pf)Pu-240 reaction. Two-vibrational resonance groups centered at E* = 4.6 MeV and 5.1 MeV, and attributed to the excitation of three and four beta -phonons, were resolved into individual substates, which could be assigned to the low-spin members of K-pi = 0(+) superdeformed (SD) rotational bands. In the region of the lower E* = 4.6 MeV resonance individual moments of inertia of six well separated bands could be extracted for the first time with values of Theta/(h) over bar (2) around 157 MeV-1, close to that of the ground state band in the second well. From the level density of these K-pi = 0(+) band heads the excitation energy of the SD ground state was determined to (2.25 +/- 0.20) MeV, in agreement with earlier estimates from excitation functions. (C) 2001 Elsevier Science B.V. All rights reserved.