Nature of low-lying electric dipole resonance excitations inGe74

Abstract

Isospin properties of dipole excitations in74 Ge are investigated using the (α, α ′ γ) reaction and compared to (γ, γ ′ ) data. The results indicate that the dipole excitations in the energy region of 6 to 9 MeV adhere to the scenario of the recently found splitting of the region of dipole excitations into two separated parts: one at low energy being populated by both isoscalar and isovector probes and the other at high energy, excited only by the electromagnetic probe. RQTBA calculations show a reduction in the isoscalar E1 strength with an increase in excitation energy which is consistent with the measurement.

Relevance of the Nuclear Structure of the Stable Ge Isotopes to the Neutrino-less Double-Beta Decay of 76Ge

“…By necessity, the details will be presented in a future, larger publication [19], so only a summary is given here. We remain cognizant of previ-ous work and these contributions to our knowledge of the nuclear structure of 74 Ge [13][14][15][16][17][18].…”

“…The structure of this region is not simple, as previous work has provided evidence of shape transitions, shape coexistence, and triaxiality [7][8][9][10][11][12]. In the case of 74 Ge, the first additional nucleus in the region we have chosen to study, a great deal of information is available from other studies [13][14][15][16][17][18]; however, some of these works are very dated and there is need for improvement. Figure 1.…”

Isospin dynamics in nuclear structure

“…[44] the ( 10 Be, 10 B[1.74 MeV]) charge-exchange reaction at 100 AMeV was presented as a new probe, which is capable of isolating the isovector (∆T = 1) non-spin-transfer (∆S = 0) nuclear response. The N=Z neutron deficient nucleus 28 Si was chosen for this study at the National Superconducting Cyclotron Laboratory (NSCL). A secondary 10 Be beam produced by fast fragmentation of 18 O nuclei at the NSCL Coupled Cyclotron Facility, the dispersion-matching technique with the S800 magnetic spectrometer, and the high-precision γ-ray tracking with the Gamma Ray Energy Tracking Array (GRETINA) were used to obtain a clean ∆S = 0 excitation-energy spectrum in 28 Al 2017 and dipole contributions were extracted through a multipole decomposition analysis, and, thereby, the isovector giant dipole (IVGDR) and the isovector giant monopole (IVGMR) resonances were identified.…”

“…The N=Z neutron deficient nucleus 28 Si was chosen for this study at the National Superconducting Cyclotron Laboratory (NSCL). A secondary 10 Be beam produced by fast fragmentation of 18 O nuclei at the NSCL Coupled Cyclotron Facility, the dispersion-matching technique with the S800 magnetic spectrometer, and the high-precision γ-ray tracking with the Gamma Ray Energy Tracking Array (GRETINA) were used to obtain a clean ∆S = 0 excitation-energy spectrum in 28 Al 2017 and dipole contributions were extracted through a multipole decomposition analysis, and, thereby, the isovector giant dipole (IVGDR) and the isovector giant monopole (IVGMR) resonances were identified. The results show that this probe is a powerful tool for studying the elusive IVGMR, which is of interest for performing a stringent test of theoretical approaches at high excitation energies and for constraining the bulk properties of nuclei and nuclear matter.…”

“…The method has been applied successfully to excitation spectra of various closed and open-shell medium-mass spherical nuclei [15,[18][19][20][21][22][23][24]. It has described well both high and lowenergy parts of the spectra including the giant multipole resonances, the isospin splitting of the pygmy dipole mode [25][26][27][28], isoscalar dipole modes [29,30], and stellar reaction rates of the r-process nucleosynthesis [31]. The improvements in the description of excited states is related to the respective advancements in the single-particle sector [32][33][34][35][36].…”