Properties of rotational excitations in odd mass Dy isotopes

Abstract

The data on high-spin rotational states in ~55Dy, ~57Dy, 159Dy and 161Dy are discussed within a model where a particle is coupled to a rotor with a variable moment of inertia. In this model there is often a definite improvement in the quality and stability of the fits to levels in the positive-parity band below spin 25/2 when the moment of inertia of the core exhibits a linear dependence on the square of the rotational angular velocity as compared to the situation where a linear dependence on I(I + 1) is assumed. In the improved fits the empirical matrix elements of the Coriolis force exhibit a smooth and significant increase with decreasing moment of inertia. The rotational energies above spin 25/2 in the positive-parity band and above 19/2 in the 11/2-[-505] band are understood within the present theoretical model if the moment of inertia increases more rapidly than the linear trend established at lower spin. In the 11/2-[505] band this increase follows rather closely the behaviour in the even nuclei whereas in the positive-parity band the curves are quite flat even beyond the point where the moment of inertia in the even nuclei exhibits a discontinuous or back-bending behaviour. The significance of this observation is discussed in the light of existing theories on nuclear moments of inertia.

The Isomeric 9/2+and the Lowest 7/2-State in the Weakly Deformed N = 89 Nuclei

“…3 comes from the 45.2 keV Kcv2-line of Dy. The observed energy (45.5 keV) of the f -+ ftransition is in agreement with the direct reaction data [3] and with the (a, 3wy) study [2], but disagrees with the results deduced from the (12C, xny) reaction [ 151. The tentatively assigned half-life T,,, -5.5 ns in Table I Thisexperiment.…”

“…3. Both distributions contain a prompt component and a 4 6 ns delay on a background, which is possibly caused by the feeding from an isomeric 6 p s ystate at 234.2keV [2]. The model prediction for the half-life of the y' state at 154.4 keV [ 21 is about 51-1s (see also Fig.…”

Coriolis Interaction

“…1 For several years it has been generally accepted 1 ' 2 that the particle-plus-rotor model 2 (PRM) is able to reproduce Coriolis-distorted bands quantitatively only if the strength of the Coriolis interaction is considerably reduced; this has remained as an outstanding puzzle in these calculations. In order to compensate for the supposedly too large Coriolis matrix elements purely ad hoc attenuation factors have been introduced., 1 It has also been asserted 3 * 4 that such a problem does not appear if the cranking model (CM) is applied. In this Letter I show that a complete treatment of the PRM gives indeed a satisfactory answer.…”