Very High Spin Yrast States and the Link to the Continuum

Abstract

The population of the yrast states of ¹⁵²Dy has been measured as a function of the angular momentum input, l_max, in the ¹²²Sn (³⁴S, 4n)¹⁵²Dy reaction. For l_max 57, states with spins of up to 29 receive ~ 90% of the channel cross-section, indicating little or no side-feeding below this spin, and the population of states with higher spin does not increase with l_max. The increased angular momentum input is reflected in the continuum γ spectrum, which show an enhanced yield around 1.3 MeV of stretched quadrupole character and around 0.6 MeV of stretched dipole character. These observations imply that the deexcitation of high-l events (l 30) is not feeding the yrast line directly via statistical transitions, but is diverted by continuum cascades and only reaches the yrast line in the spin interval between 30 and 38. Several possible reasons for this behavior are suggested.