Level structure ofNd140

Abstract

The structure of ' Nd has been studied via the ' Te("0,4n) ' Nd and '"Te(' 0,4n) ' Nd reactions at beam energies from 64 to 76 MeV and 72 to 76 MeV, respectively. In beam y-ray spectroscopy techniques, including y-ray excitation functions, y-y coincidences, and y-ray angular distribution measurements, were used to construct a level scheme up to J =17 at an excitation energy of 6411 keV. Definite parity assignments were made up to the 11+ state. Two-particle configurations were calculated with a shell model and a modified surface delta interaction.

Evolution from spherical single-particle structure to stable triaxiality at high spins inNd140

“…The results of the present study confirm the main features of the level scheme published previously [25]. First, we clearly see the low-energy 90-keV transition between the 6 + and 5 − states.…”

“…1 and 2. The most recent previous study of the level scheme dates back to 1987 [25]. In that work the level structure was established up to spin 17.…”

“…Three isomers were previously identified with lifetimes between 0.25 ns and 0.6 ms. They are the 7 − state at 2221 keV with 0.6 ms [28], the 10 + level at 3619 keV with 32(1) ns [25,29], and possibly an I = 12 isomer at 4512 keV with 0.25 ns [30].…”

“…Previously, only spherical or near-spherical states up to spin 17 were known in this nucleus [25]. In Secs.…”

High spin spectroscopy of 137La

“…The presence of seven extra-core protons beyond the Z = 50 shell closure places the nucleus at the middle of the Z = 50-64 sub-shell where one may expect to observe a growth of collective behaviour in the level structure, in particular, at higher spin and excitation energy, in which, the π1h 11/2 intruder orbital has an important role to play. From the systematics of low-lying states in even-A, N = 80 isotones [1], the existence of 10 + isomers at a modest excitation energy, has been confirmed as arising due to two neutron holes in ν1h 11/2 orbit. From shell model systematics, it is known that the π2d 5/2 and π1g 7/2 single particle orbits lie very close to each other, thereby making the proton Fermi surface rather diffused.…”