Single-proton states in 155Eu

Abstract

The [Formula: see text] reaction was studied using 17 MeV polarized tritons from the tandem Van de Graaff accelerator at the Los Alamos Scientific Laboratory. The alpha particles were analyzed using a Q3D magnetic spectrometer and detected with a helical-cathode position-sensitive counter. The overall resolution was ~ 18 keV FWHM. Some additional exposures, performed using unpolarized tritons on a thinner target, had a resolution of ~ 12 keV FWHM and were helpful in the interpretation of a number of multiplets. Measurements of the 154Sm(α,t)155Eu reaction were made using 25 MeV alpha beams from the McMaster University tandem accelerator. The triton spectra were analyzed with a magnetic spectrograph using photographic emulsions for detectors, yielding a resolution of ~ 10 keV FWHM. By comparing the measured angular distributions of [Formula: see text] cross sections and analyzing powers with DWBA predictions it was possible to assign spins and parities to many levels. The present results confirm earlier assignments of rotational bands based on the low-lying 5/2+[413], 5/2−[532], and 3/2+[411] orbitals. In addition, states at higher excitation have now been assigned to the 1/2+[411], 1/2+[420], and 7/2+[404] orbitals, and a 3/2+[422] band is tentatively proposed. The spectroscopic strengths can be explained reasonably well by the Nilsson model when pairing and Coriolis mixing effects are included.