Proton States of Deformed Nuclei with A = 153 to A = 163

Abstract

<p>Proton states of ¹⁵³Eu, ¹⁵⁵Eu, ¹⁵⁵Tb, ¹⁵⁷Tb, ¹⁵⁹Tb, ¹⁶¹Tb, and ¹⁶³Ho have been studied using the (α,t) and (³He,d) reactions. Beams of 24 MeV ³He and 25 MeV alpha particles were produced by the McMaster University model FN tandem Van de Graaff accelerator. The reaction products were analyzed with an Enge split-pole magnetic spectrograph and detected with photographic emulsions. Ratios of the cross sections between the (α,t) and (³He,d) reactions were used as an indication of the ℓ-values for the proton transfers, and the spectroscopic factors were extracted using DWBA calculations. Interpretation of the results is made in terms of the Unified Model.</p> <p>The results of the present work confirm the assignments of the 3/2⁺[411] and 5/2⁺[413] Nilsson orbitals in the terbium isotopes. The I = II/2 members of the 5/2⁻[532] and 7/2⁻[523] orbitals are identified in ¹⁶¹Tb and ¹⁵⁹Tb and their assignments confirmed in ¹⁵⁷Tb and ¹⁵⁵Tb. It is necessary to invoke appreciable Coriolis mixing between these two orbitals in order to describe the observed rotational level spacings and the spectroscopic strengths. The assignment of the 7/2+[404] orbital is confirmed in ¹⁵⁵Tb and ¹⁵⁷Tb and this orbital is identified in ¹⁵⁹Tb and ¹⁶¹Tb. Previous assignments of the 1/2⁺[411] particle state with vibrational admixtures are confirmed in ¹⁵⁷Tb and ¹⁵⁹Tb and the state is identified in ¹⁶¹Tb. The present results support the earlier evidence for the existence of a second fragment of the 1/2⁺[411] orbital in ¹⁵⁹Tb and suggest the presence of a similar state in ¹⁵⁷Tb. The assignment of the the 5/2⁺[402] orbital is made and tentative assignment of the 1/2⁺[411] orbital is considered for each of the terbium isotopes. In ¹⁶³Ho, the assignments of the 7/2⁻[523] and 7/2⁺[404] orbitals are confirmed, and strong evidence for the assignment of the 3/2⁺[411], 1/2⁺[411], 5/2⁺[402] and 1/2⁻[541] orbitals is found. In the europium isotopes, the assignments of the 5/2⁺[413], 3/2⁺[411] and 5/2⁻[532] orbitals are confirmed, and evidence for the assignment of the 7/2⁻[523], 1/2⁺[411], 7/2⁺[404] and 1/2⁻[541] orbitals is considered.</p>