Zdependence of theN=152deformed shell gap: In-beam γ-ray spectroscopy of neutron-richPu

Abstract

We have measured in-beam γ rays in the neutron-rich 246 Pu 152 and 245 Pu 151 nuclei by means of 244 Pu( 18 O, 16 O) 246 Pu and 244 Pu( 18 O, 17 O) 245 Pu neutron transfer reactions, respectively. The γ rays emitted from 246 Pu ( 245 Pu) were identified by selecting the kinetic energy of scattered 16 O ( 17 O) detected by Si E − E detectors.The ground-state band of 246 Pu was established up to the 12 + state. We have found that the shell gap of N = 152 is reduced in energy with decreasing atomic number by extending the systematics of the one-quasiparticle energies in N = 151 nuclei into those in 245 Pu. This reduction of the shell gap clearly affects the 2 + energy of the ground-state band of 246 Pu.

One-quasiparticle bands in neutron-richW187

“…In the present work, we employed an in-beam γ -ray spectroscopic method to investigate higher spin states of 187 W populated in an 18 O-induced one-neutron transfer reaction. This type of experimental technique is effective for the investigation of near-yrast structure in moderately neutron rich nuclei [8][9][10][11][12][13].…”

Development of a measurement system for the determination of (n,γ) cross-sections using multi-nucleon transfer reactions

“…As mentioned above, in this facility we have carried out in-beam γ-ray spectroscopy by using HPGe detectors to observe the deexcitation γ-rays from the nuclei produced by the multi-nucleon transfer reactions in coincidence with the outgoing particles detected by the Si ΔE-E detector system [19][20][21][22]. In the present study, we have used two anti-Compton LaBr 3 (Ce) spectrometers to measure γ-rays from the populated compound nuclei, and an improved Si ΔE-E detector system to detect outgoing particles from multi-nucleon transfer reactions.…”

“…In addition, we have much experience in the in-beam γ-ray spectroscopy with the heavy-ion projectiles; e.g. we have measured de-excitation γ-rays in neutron-rich nuclei of 236 Th, 240, 242 U, 246 Pu, and 250 Cm using the ( 18 O, 16 O) and ( 18 O, 20 Ne) two-nucleon transfer reactions [19][20][21][22].The method employed in these experiments is common with the surrogate reaction method. Namely, both in the surrogate reaction method and in the in-beam γ-ray spectroscopy, one has to measure the γ-rays emitted from the excited states in the nuclei populated by the (multi-)nucleon transfer reaction or the inelastic scattering, in coincidence with outgoing particles.…”

“…As for the γ-ray detector, we selected a LaBr 3 (Ce) scintillation detector instead of the High Purity Germanium (HPGe) detectors used in the previous in-beam γ-ray spectroscopy [19][20][21][22]. The use of the LaBr 3 (Ce) scintillation detector has an advantage on larger intrinsic detection efficiency than the detectors such as HPGe [23], NaI [24], and C 6 D 6 [25] detectors used in the previous surrogate reaction method, due to relatively high effective atomic number and high density of material contained in the scintillator.…”

αdecay of97249Bk and levels in95245Am

“…This fixes the parity of these two levels as positive. The β − decay of 245 Pu, which has a 9/2 − [734] ground-state configuration [18,19] In Refs. [1,7], levels at 28.0, 70.4, 124.6, and 190.8 keV were deduced from the transitions deexciting higher-lying states in 245 Am and these were assigned to the 5/2, 7/2, 9/2, and [7].…”