The structure of the deformed nucleus 42 103 Mo61

Abstract

Abstract. The lifetimes of the three lowest excited members of the rotational ground-state band of 1~ at 102.6, 241.1 and 433.2 keV as well as of the levels at 353.8 and 456.1 keV have been determined through a measurement of the delayed coincidences between/~ particles from the decay of the parent l~ and the 7 rays which depopulate the levels. A plastic and a BaF 2 detector have been used for the /~ and 7 rays, respectively, in these experiments at the fission product separator JOSEF. The results for all three band members evince that this nucleus has a sizeable deformation, with a value of/3q=0.34(1). This value is larger than that of the neighbouring eveneven Mo isotopes which indicates an odd-even effect. On the other hand it confirms the observation that the Mo nuclei are in general less strongly deformed than their Sr and Zr isotones. Particle-rotor model calculations with the Nilsson parameters ~c = 0.084, j~ = 0.28 provide a good description of the ground-state band and of a side band based on the 346.5 keV level, including the new lifetimes. This substantiates the Nilsson orbital assignments of [41113/2 + and [532]5/2-for these two bands, respectively, where the sideband is strongly affected by a [54113/2-admixture. There is evidence for an additional band based on the 641.1 keV level for which the assignment [42213/2 + is proposed.

Lifetime measurements and particle-rotor calculations for 42 105 Mo63

“…It is important to note that this value is definitely larger than that of fiq=0.31 (1) and 1~ respectively, and of fiq=0.34(1) for ~~ [8]. It is comforting to note that the values obtained from the half-lives of both the first and second excited states in l~ are in perfect agreement, which confirms the interpretation of the low-lying levels of this nucleus as a rotational band.…”

“…The energy has a minimum close to the experimentally determined value of/~q = 0.38 ~ 6 2 = 0.31. The properties of l~ have been calculated [18] with the Particle-Rotor model [19] using the parameters of x = 0.084 and p = 0.28 which have been determined recently [8] for 1~…”

“…In addition, new information on level lifetimes was desired in order to obtain data relevant for a comparison with the results of calculations based on rotational models. Of interest is the question whether the new set of Nilsson-parameters determined for l~ [8] can also be used for a description of ~~…”

Structure of the highly deformed nucleus101Sr63 and evidence for identical K=3/2 bands

“…The parameter a = 3.9(4) differs considerably from the value of 0.315 from the liquid-drop estimate, indicating a much stronger dependence on deformation. It is even more remarkable that the data for the [41113/2 bands in the N = 61 isotones 99Sr [6], l~ [16] and 1~ [30] can be fitted by the same function, only shifted by an additional term 6J0 = 0.21 x J0 which accounts for the contribution of the odd neutron to the moment of inertia. For comparison, in Fig.…”

“…This assignment is based on level systematics, according to recent results on its isotone l~ [17] and the new assignment of the ground-state band in l~ [27,28] In 99Sr6l, the exact location of the [532]5/2 orbital is not known, but it has recently been assigned to the 216.7keV level in l~ [16,17], and in 1~ it is very likely at 346.5 keV [16,30]. In all known cases, the [532]5/2 band appears to be perturbed by Coriolis interaction.…”