Spectroscopy ofGd153andGd157using the

T. J. Ross

¹

,

R. O. Hughes

²

,

J. M. Allmond

³

et al.

Abstract

Low-spin single quasi-neutron levels in 153 Gd and 157 Gd have been studied following the 154 Gd (p,d-γ) 153 Gd and 158 Gd(p,d-γ) 157 Gd reactions. A combined Si-telescope and HPGe array was utilized, allowing d-γ and d-γ-γ coincidence measurements. Almost all of the established lowexcitation energy, low-spin structures were confirmed in both 153 Gd and 157 Gd. Several new levels and numerous new γ rays are observed in both nuclei, particularly for Ex ≥ 1 MeV. Residual effects of a neutron sub-shell closure at N = 64 are observed in the form of a large excitation energy gap in the single quasi-neutron level schemes.

Semiclassical calculations for the Gd156 (p,d) reaction

“…The experimental angular momentum transfer L=0 data of Allmond et al [10] and L=0 DWBA [11] angular distributions for the direct population of the 367-keV, Ross et al [4]. The graph shows the DWBA angular distributions fit which is best characterized by L=0,1,4.…”

“…The p,d reaction states 1 2 + [400] in 155,157 Gd and their relative intensities of Ref. [10,4], are shown in Table I. TABLE I.…”

“…[10] and VII of Ref. [4]. The relative yields for levels directly populated by the 156 Gd(p,d) 155 Gd and 158 Gd(p,d) 157 Gd reactions are indicated.…”

“…Inspired by the doctoral thesis of Tim Ross [1] under the guidance of Prof. Con Beausang, and the data in their three publications with colleagues [2,3,4] we have undertaken to develop a semi-classical theoretical model to both the 156 Gd (p,p) and 156 Gd (p,d) reactions. The experimental data mostly come from collaboration at cyclotrons at Lawrence Berkeley National Lab and at the Texas A & M cyclotron in College Station, TX.…”

“…We attempt to rationalize some of the patterns of Fig. 2 [10,4], but without invoking the double-BCS model of S.Y. Chu et al [6] in which the BCS equations are applied separately to the upgoing and downgoing Nilsson levels as quadrupole deformation increases.…”