Yrast Traps and Very High-Spin Yrast States inDy152

Abstract

We have identified yrast states of 152 Dy to spin ~37, with unusually strong population of high-spin states in the ( 32 S,4wy) reaction. Yrast isomers with spins ~17, 21, 27, and 31 were detected. For J ^ 14 the yrast states scatter about a straight line on an E vs IQ +1) plot, consistent with predictions for aligned-p article configurations. The slope of the line yields an effective moment of inertia 18% larger than the rigid-sphere value. This and other arguments suggest possible oblate deformation at high spin.Investigations of high-spin nuclear states, / > 3Qfr, have so far been limited to studies of continuum y radiation. 1 ' 2 Such experiments by their nature provide information only on gross properties of nuclear states over a wide range of excitation energy above the yrast line. Data on the yrast line itself to very high spin will open up a domain of nuclear structure which has hitherto not been explored. In particular one might learn whether there is a general relation between the energies and spins of yrast states, as has been predicted for an independent-particle system, 3 and how shell effects modify this relation; whether dramatic shape changes are induced in nuclei by large angular moments; and how spin is generated with the least expenditure of energy.

Nuclei at High Angular Momentum

“…Radioactive decay was the first. Early evidence for shell~model isomers came mostly from s~decay studies (Goldhaber and Sunyar 1951), and a-decay provided systematic evidence (Khoo al 1978) and an average~ with hard work~ might be 30h. Other experimenters have developed techniques to extract information from unresolved spectra.…”

Anomalies in the rotational spectra of deformed nuclei

“…В этой модели ядро вращается классически с угловой скоростью Ω. Для того, чтобы вычислить энергию вращения, следует перейти во вращающуюся систему координат. Гамильтониан аксиально-деформированного ядра в этой системе будет иметь вид H'=H-QR^ (6) где Η -гамильтониан покоящегося ядра, а R x . -проекция момента вращения ядра на ось х', перпендикулярную к оси симметрии ζ'.…”

Phenomena at Very High Spins

“…The correlated spectrum for the system *2 4 The interpretation of these data is somewhat speculative, but promises to be quite interesting. The type of decay pathway envisioned is illustrated in Fig.…”

“…The first level scheme to be worked out up to spins as high as 36-fc was that of 152 Dy studied by Khoo et al 4 It. is shown in Fig.…”