Structure of high spin states in83Y

Abstract

We report on the first in-beam study of high spin levels in 83y which were established up to 9.0 MeV excitation energy and probable spin of 41/2 + resp. 27/2-by means of the reaction 58Ni(28Si, 3p). Ten lifetimes and six lifetime limits in the 10 -lz-10-9s range were determined in two recoil distance Doppler shift experiments. The positive parity yrast states form a g9/2 Coriolis decoupled band with partial alignment, near-rigid rotor moment of inertia and deformation//2 =0.29. The negative parity yrast band has very similar collective properties; it shows a pronounced band crossing at rotational frequency hco~0.40 MeV which we associate with twoquasiparticle g9/2 proton alignment. At 2.56 MeV excitation, a second AI=I band starting with 17/2-was found. On the basis of the similarity to 85y and the very weak E2 decay of this state, we suggest that this band has (3qp) configuration with an aligned g9/2 neutron pair. The lifetimes of the lowest 2 + and 4 + state in S~Zr populated in the reaction SSNi (2sSi, 2p) were determined to be z(2)= 17.8(11) ps resp. z(4)= 3.5(4) ps.

Table of Magnetic Dipole Rotational Bands

“…A total of 120 bands in 56 nuclei from four mass regions have been compiled from the literature. Some additional cases, namely 83 Y [28,29], 83 Zr [30], 106 Cd [31], 103,105,107,109 In [32,33], 117 I [34], 128 Ba [35], and 139 Pm [36], are also likely candidates of MR bands but have not been included in this Table due to the uncertain nature of the bands and insufficient information. The bands in the A ϭ 80 and 135 regions and Hg nuclides included in the Table should also be treated with caution.…”

Rotational and single-particle structures in83Zr

“…3. Here, the DCO ratios of transitions with known multipolarities in 83y, 83Zr ' 84Zr and S~ [5,14,15] populated in this work are plotted versus the respective initial spin. It is found that by gating on a known coincident stretched E2 transition, a quadrupole transition would produce Roco = 1.1, while a stretched 5oo0-GATE:I)0keV N3 ~., …”

“…1. The curves show the mass gated distribution of ),-ray yields for known transitions, in 83y, 83Zr and 83Nb [5,14,15,23] as a function of energy loss, AE. By setting gates in the mass gated AE spectrum and carefully subtracting 83y and a3Nb, a spectrum of 83Zr with many new transitions is obtained, shown in the middle portion of Fig.…”

Nuclear structure of odd-oddY82

“…The rotational bands in Y have been analyzed in the framework of the cranking model 18], along with the nearby N = 43 isotones solb and s~'Nb and Z = 39 , isotopes ( Y [19] and ssY [20]). times rather high at low frequencies, but become quite constant above 0.4 MeV/h where they lie in the range of 20 to 25 h /MeVapproximately the rigid rotor value.…”