Higher-spin structures inF21andNa25

Abstract

Excited states were investigated in 21 F and 25 Na using the 9 Be( 14 C,pnγ) reaction at 30, 35, and 45 MeV and the 9 Be( 18 O,pnγ) reaction at 35 MeV. Protons were detected and identified in an E-∆E telescope at 0 o in coincidence with one or more γ radiations in the FSU Compton-suppressed Ge detector array. Many new levels and electromagnetic decays were observed, especially among the higher spin states. Angular distributions and mean lifetimes were measured wherever possible in both nuclei. The energy levels of the positive-parity states in the two nuclei agree rather well with shell model calculations using both the USDA and WBP interactions up to the highest spins observed of 13/2h. Both a weak coupling approximation and shell model calculations using the WBP interaction generally reproduce the negative-parity states in 21 F. The shell model calculations reproduce relatively well the measured M1 and E2 transitions in both nuclei, but overpredict the parity-changing E1 transitions in 21 F, the only nucleus in which negative-parity states were observed in the present experiment.

Measurement of key resonances for the Al24(p,γ)Si25 reaction rate using in-beam Longfellow1, Gade2, Brown3 et al. 2018Phys. Rev. CSelf Cite

“…7. The spin-parities for these levels in the mirror nucleus were definitively assigned using the d ( 24 Na,p) 25 Na reaction [16] consistent with [15]. The 670 and 1315 keV transitions were populated strongly in the 9 Be( 25 Al, 25 Si)X reaction and were not observed in the SeGA experiments, in which 25 Si was produced from one-neutron knockout.…”

“…Details on the USDB+CD+TE(-0.325) interaction, which includes charge-dependent parts and a Thomas-Ehrman shift of 0.325 MeV for the proton 1s 1/2 orbital, are given in the discussion section. For 25 Na, branching ratios and spin-parity assignments are taken from [15] and [16] when available and otherwise taken from [23]. Transitions from the 9/2 + 2 and 9/2 + 1 states are indicated in blue and transitions from the 9/2 + 3 and 7/2 + 1 states in green to highlight the identification of the (9/2 + ) resonance at the center of our work.…”

“…Two resonances above the proton separation energy were observed from their γ-ray decays. Our 25 Si level scheme is compared to shell-model calculations and the mirror nucleus [15,16] and an updated 24 Al(p,γ) 25 Si reaction rate calculation is presented.…”

Radiative decay of neutron-unbound intruder states inO19

“…Decay properties of unbound states in 19 O from the present experiment and Ref. [13] below 6.3 MeV are compared in Table I along with possible correspondences with pdsu shell model states.…”

“…Examples are states with complex structure often involving intruder configurations. This was the first study of 19 O using a heavy-ion fusion reaction which favors population of higher-spin states and employs a modern γ detector array. The α-γ and mostly α-γ-γ coincidences were analyzed to build upon the previously known level and decay scheme.…”