Universality of decay-out of superdeformed bands in the 190 mass region

Abstract

Superdeformed nuclei in the 190 mass region exhibit a striking universality in their decay-out profiles. We show that this universality can be explained in the two-level model of superdeformed decay as related to the strong separation of energy scales: a higher scale related to the nuclear interactions, and a lower scale caused by electromagnetic decay. Decay-out can only occur when separate conditions in both energy regimes are satisfied, strongly limiting the collective degrees of freedom available to the decaying nucleus. Furthermore, we present the results of the two-level model for all decays for which sufficient data are known, including statistical extraction of the matrix element for tunneling through the potential barrier.

Population and decay of superdeformed nuclei probed by discrete and quasi-continuum γ-ray spectroscopy

“…A somewhat different approach to the barrier dynamics has been given by Barrett et al, combining the two-level model with an asymptotically exact quantum tunnelling interaction. [127,128]. The results are in overall agreement concerning the actions S from Eqs.…”

Determining the energy barrier for decay out of superdeformed bands

“…To make contact with experiment, the tunneling matrix element may be estimated using the two-state model of SD decay [7,10,15], which assumes the decay-out process is dominated by coupling of each SD state with its nearest-lying energy level in the ND band. The branching ratios F N and F S = 1 − F N for decay out and intraband decay, respectively, are determined by three rates [10]:…”

“…Their rapid decay-out, in particular, has been the subject of great interest (e.g., Refs. [2][3][4][5][6][7][8][9][10][11][12][13][14][15]). In the standard theoretical approach [2,3], this process is modeled by a two-well potential function of deformation: Here, the nucleus is a single quantum mechanical particle, which tunnels between the two wells, and can escape the system via electromagnetically induced decay from either.…”

Random Matrix Theory and Its Application to the Decay Out of a Superdeformed Band

“…However, very recently this approach was used to analyze the data in the 190 mass region. 48 As was mention at the beginning of this section, in the 190 mass region, the decay from the SD to the normal states is spread over many different available paths. This means the SD state are coupled to many ND states.…”