The 159Tb(t, α)158Gd reaction with 17 MeV polarized tritons

The 159Tb(t, α)158Gd reaction has been studied using 17 MeV polarized tritons from the Los Alamos Scientific Laboratory Tandem Van de Graaff accelerator. The α -spectra were analyzed with a Q3D magnetic spectrometer. The observed analyzing powers for most of the strong transitions have large magnitudes similar to those observed for (t, α ) studies with neighbouring even-even targets. This is consistent with a Nilsson model description of the two quasiparticle states populated in 158Gd, in which most of the strong transitions would be expected to be dominated by a single j-value. The present results provide strong confirmation of the previously suggested assignments of the 1380 keV (Kπ = 4+) and 1930 keV (Kπ = 1+) band heads as 52+[413] ± 32+[411] configurations. Several rotational members of the Kπ = 1− octupole band were populated via the 52−[532]-32+[411] component of this vibration, and from the observed strengths it is estimated that this two-quasiparticle admixture makes up ∼45% of the octupole vibration. Strong transitions to several levels above 2 MeV excitation are dominated by l = 5, j = 112 transfers, and these are ascribed to pickup of a 52−[532] proton. The spin 5, 6 and 7 members of the Kπ = 4−, 52−[532] + 32+[411] band have been assigned at 2176 keV, 2282 keV and 2418 keV, respectively. Whereas previous studies have shown that the (t, α) reaction with polarized tritons is a very useful specroscopic technique when used with even-even target nuclei, the present results extend the proven effectiveness to cases of odd-mass deformed targets.