E1,ΔK=0−Übergänge in deformierten Kernen ungerader Massenzahl

Abstract

The half lives of the 5/2 5/2⁻[523] level at 25.7 keV in ¹⁶¹₆₆ Dy and the 5/2 5/2⁺[642] level in ¹⁶³₆₈ Er, found in this work to lie at 69.2 keV, have been determined by the delayed coincidence method to be T_1/2=27.8± 1.5 nsec, and T_1/2=8.8± 0.5 nsec, respectively. The following hindrance factors relative to the single particle Weisskopf estimate (F _W and the Nilsson estimate (F_N were obtained: ¹⁶¹₆₆ Dy 5/2 5/2⁻[523] → 5/2 5/2⁺[642]:F_W=(6.6± 1.3) × 10³, F_N=0.48± 0.10 ¹⁶³₆₈ Er 5/2 5/2⁺[642] → 5/2 5/2⁻[523]:F_W=(2.4± 0.5)× 10⁴, F_N=1.8 ± 0.4

A systematic difference between transitions in odd proton nuclei and odd neutron nuclei was found: E1, ΔK=0 transitions in odd neutron nuclei have hindrance factors F_N from 2.9 to 0.16, this means, these transitions are in agreement with the predictions of the Nilsson model within a factor of 10. For transitions in odd proton nuclei one has hindrance factors F_N from 75 to 9.9 × 10⁻⁴. It is shown that a small difference between the deformation of the initial and the final state changes the transition probability of both, proton and neutron transitions, considerably.