De-excitation of even-even isotopes of Yb, Hf and W produced in (p, xnγ) reactions

The population of ground state rotational bands in the even-even deformed nuclides 166,168Yb, 170,172,174Hf, and 178,180 W has been observed in reactions induced by 18 to 57 MeV protons. Detailed calculations are performed on the basis of the statistical model of the compound-nucleus-reaction de-excitation process, and it is concluded that the experimental results can be satisfactorily explained. The mean moments of inertia of the nuclei produced in the reactions are deduced, for an estimated residual excitation energy of 6 MeV, and found to amount to no more than 50 % of the corresponding rigid sphere figures. The obtained values are compared, and shown to be in agreement, with the previsions of the independent pairing model of Lang and Le Couteur.