Angular distribution studies in ^{172, 174}Yb

Abstract

Levels in ^{172, 174}Yb have been studied using the (n, n'γ) reactions with reactor fast neutrons. Angular distributions of γ-rays with respect to the neutron beam have been measured. Ambiguities involving the 1640.7 keV level in ¹⁷²Yb and the 2101.2 keV level in ¹⁷⁴Yb have been resolved revealing spin-parity assignments of 4⁻ and 4⁺ respectively. Seven new states at 2320.7, 2350.4, 2436.5, 2601.2, 2796.0, 3403.0 and 3427.0 keV have been proposed in ¹⁷⁴Yb. The 2601.2 and 3403.0 keV levels have been assigned as J^π = 4⁺ and J^π = (3, 5⁻) respectively. Gamma branching ratios have been determined and compared with previous results. The mixing ratios for several γ-transitions have been deduced and compared, where possible, with values obtained by the complete alignment method (CAM) and with those previously reported by other authors. The experimental levels in ^{172, 174}Yb have been compared with IBA model predictions.