Richard Hadsell

To test the validity of macroscopic nuclear models with respect to their description of states having large angular momentum, a search for previously unobserved high spin states of nuclei in the mass region A = 21-23 was conducted. In particular, it has been expected that the prediction of rota­ tional band termination, made by microscopic models with truncated configura­ tion spaces, could be compared with observations of states lying near or perhaps even above the predicted termination.

The nuclei ²¹Ne, ²²Ne, and ²³Na were investigated using the reactions ⁹B(¹⁶O, dγ)²³Na, ⁹Be(¹⁶O, αγ)²¹Ne, ¹²C(¹³C, αγ)²¹Ne, and ¹³C(¹³C, αγ)²²Ne. Particle detection efficiency was increased, without allowing angle-dependent energy shifts to degrade the resolution, by employing a radially position-sensitive detector subtending emission angles from 0° to 15°. Coincidence observations utilized both NaI and Ge(Li) detectors for the gamma rays, and angular correlations in Litherland-Ferguson Method II geometry were measured for states in ²²Ne.

Contrary to expectations, on the reaction ⁹Be(¹⁶O,d)²³Na appeared to populate how spin states selectively in the residual nucleus. Furthermore, no new members of the ground-state rotational bands could be identified. Failure to observe the gamma decay of the expected 15/2⁺ member of the ground-state band in ²¹Ne leads to the suggestion that such a state decays primarily by alpha or neutron emission.

The measurements reported here unfortunately indicate that heavy-ion induced reactions will be somewhat less useful in probing high angular momen­tum nuclear configurations than earlier, more preliminary measurements have suggested.