S.R. Faber

A study of 172Yb following the 170Er(α, 2n) reaction

Abstract Six side bands have been identified up to high spin in 172 Yb. Four of these, with K π = 1 − , 4 − , 6 − and possibly 9 − , involve an i 13 2 neutron, and have high moments of inertia. The properties of these bands are reproduced in a two-quasiparticle-plus-rotor Coriolis coupling calculation. A well-known band with K π = 3 +; is extended to I = 14; its properties suggest a mixed neutron-proton configuration. The first excited K π = 0 + band is extended to I = 14. It has a rapidly rising moment of inertia, and is predicted to cross the g.s.b. at about I = 20 + . These K = 0 + states could be the low-spin members of an ( i 13 2 ) 2 band.

Rotational bands in 170Yb observed following (α,xn) reactions

Abstract At least seven side bands, with Kπ = (0+), (1−), (2+), (3−), 4−, 6−, and 7−, have been identified in 170Yb up to high spin, using γ-ray techniques following (α, 2n) and (α, 4n) reactions. Backbending in the positive-parity yrast band is confirmed, and candidates for low-spin members of the S-band are found. The negative-parity yrast band has behaviour characteristic of both strong coupling and decoupling. These properties, together with those in the other negative-parity side bands, are interpreted as arising from Coriolis effects on the quasiparticle configurations, and the experimental results are compared with a two-quasipartiele-plus-rotor calculation. Evidence of ΔK = 2 mixing is found in the K = (3) side band. The relationship between the moments of inertia of the positiveparity and negative-parity yrast bands in the N = 100 isotones is discussed in the framework of a simple empirical model, giving insight into the presence or absence of backbending. The negativeparity yrast bands in the N = 100 isotones are compared. Their significant differences are qualitatively reprodued in two-quasiparticle-plus-rotor calculations.

High-spin neutron hole excitations in light odd-A Pb nuclei☆

Abstract The high-spin level structures of 195,197,199,201,203 Pb have been investigated by ( α , x n γ ) and ( 3 He , x n γ) spectroscopy. The resulting level schemes are interpreted in terms of the weak coupling of an ν i 13 2 hole to known states of the even- A core nuclei.

Negative-parity yrast band in 170Yb: Rotation-aligned neutrons with deformation-coupled bandhead?

Abstract A sideband in 170 Yb has been identified up to I π =17 − . It has an isomeric I =4 bandhead, yet the odd-spin states have prompt branches to the ground-state band. The contrasting properties are explained by the Coriolis effects on the quasi-particle configuration.

Observation of particle alignment in the octupole band of 172Yb

Abstract Members of the octupole band up to spin 14− have been identified with the 170 Er (α,2 n ) 172 Yb reaction. The band is strongly perturbed by Coriolis effects and has a high moment of inertia with variations characteristic of particle alignment. Vabrational alignment is insufficient to explain the data.