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Collectivity of light Ge and As isotopes

Abstract : Background: The self-conjugate nuclei of the A ∼ 70 mass region display rapid shape evolution over isotopic or isotonic chains. Shape coexistence has been observed in Se and Kr isotopes reflecting the existence of deformed subshell gaps corresponding to different shell configurations. As and Ge isotopes are located halfway between such deformed nuclei and the Z = 28 shell closure. Purpose: The present work aims at clarifying the low-lying spectroscopy of 66Ge and 67As, and providing a better insight into the evolution of collectivity in light even-even Ge and even-odd As isotopes. Methods: We investigate the low-lying levels and collectivity of the neutron deficient 67As and 66Ge through intermediate-energy Coulomb excitation, inelastic scattering, and proton knockout measurements. The experiment was performed using a cocktail beam of 68Se, 67As, and 66Ge nuclei at an energy of 70-80 MeV/nucleon. Spectroscopic properties of the low-lying states are compared to those calculated via shell model with the JUN45 interaction and beyond-mean-field calculations with the five-dimensional collective Hamiltonian method implemented using the Gogny D1S interaction. The structure evolution of the lower-mass Ge and As isotopes is discussed. Results: Reduced electric quadrupole transition probabilities B(E2) have been extracted from the Coulombexcitation cross sections measured in 66Ge and 67As. The value obtained for the B(E2; 0+ 1 → 2+ 1 ) in 66Ge is in agreement with a recentmeasurement, ruling out the existence of aminimum at N = 34 in the B(E2) systematics as previously observed. New transitions have been found in 67As and were assigned to the decay of low-lying negative-parity states.
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http://hal.in2p3.fr/in2p3-00872588
Contributor : Michel Lion <>
Submitted on : Monday, October 14, 2013 - 9:47:05 AM
Last modification on : Wednesday, November 18, 2020 - 5:12:06 PM

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A. Corsi, J.-P. Delaroche, A. Obertelli, T. Baugher, Dominique Bazin, et al.. Collectivity of light Ge and As isotopes. Physical Review C, American Physical Society, 2013, 88, pp.044311. ⟨10.1103/PhysRevC.88.044311⟩. ⟨in2p3-00872588⟩

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