Measurements of E1 transition probabilities in several deformed odd-mass nuclei as a study of single particle motion

Abstract

Lifetime measurements of nuclear states in the rare region have been performed by delayed fast-slow coincidence experiments. Results: (1) 321 keV 9 2 + individual particle state of Hf 177 , t 1 2 = (6.3±0.5) × 10 −10 sec ; corresponding to three E1 transitions with hindrance factors > 10 5. (2) 113 keV 9 2 − rotational state of Hf 177, t 1 2 = (5.2±0.4) × 10 −10 sec. (3) 396 keV 9 2 − individual particle state of Lu 175, t 1 2 = (3.1±0.3) × 10 −9 sec ; corresponding to three E1 transitions with hindrance factors of ≈ 10 6. (4) 113 keV 9 2 + rotational state of Lu 175, t 1 2 ≦ 1.5 × 10 −10 sec. The E1 transition probabilities obtained, together with those of Lu 177, 147 keV (de Waard; McGowan) and Ta 181, 6.25 keV (Hauser) are analyzed in terms of the strong coupling model. (a) The single particle wave function of the rotational levels of the K = 7 2 − ground state band in Hf 177 is perturbed, presumably by interaction with a K = 9 2 − state. (b) The five E1 matrix elements for the K = 9 2 − → K′ = 7 2 + transitions in Lu 175, Lu 177 and Ta 181 are equal within a factor < 3. From this one can infer that the considerable changes of the nuclear core features are of no significant influence on the single particle wave functions of the initial and of the final states. (c) The transition probabilities deduced from configuration mixtures for the individual particle states in a Nilsson-potential are two orders of magnitude greater than the experimental values. Reducing the configuration mixture, as e.g. recently derived by Lemmer and Green from a non-local nucleon-nuclear interaction, will improve the agreement considerably.