Single-proton states in 157Eu and 159Eu studied with the ( [formula omitted] ,α) reaction

Abstract

No nuclear structure information is available in the literature for the neutron-rich isotope 159Eu and there is conflicting evidence concerning the decay of 157Sm to levels in 157Eu. The present report describes 158,160Gd( t → , α) 157,159Eu results which provide a great deal of information on these nuclides. The experiments were performed with 17 MeV polarized tritons from the tandem Van de Graaff accelerator at the Los Alamos Scientific Laboratory. The reaction products were analyzed with a Q3D magnetic spectrometer and detected with a helical-cathode position-sensitive counter. A new, more accurate value for the mass of 159Eu has been obtained. A comparison of the measured angular distributions of (t, α) cross sections and analyzing powers' with DWBA predictions permitted the determination of spins and parities for many levels. Rotational bands have been assigned for the 5/2 +[413], 5/2 -[532], 3/2 +[411] and 1/2 +[420] orbitals in each nuclide. Also I π = 3/2 + levels have been found which are probably members of the 1/2 +[411] bands. The availability of this type of information makes it possible to extend the systematics of single particle states, and some interesting trends are discussed.