Collective excitations ofRu96by means of(p,p′γ)experiments

Abstract

Background: One-phonon mixed-symmetry quadrupole excitations are a well-known feature of near-spherical, vibrational nuclei. Their interpretation as a fundamental building block of vibrational structures is supported by the identification of multi-phonon states resulting from a coupling of fullysymmetric and mixed-symmetric quadrupole phonons. In addition, the observation of strong M 1 transitions between low-lying 3 − and 4 + states has been interpreted as an evidence for one-phonon mixed-symmetry excitations of octupole and hexadecapole character. Purpose: The aim of the present study is to identify collective one-and two-phonon excitations in the heaviest stable N = 52 isotone 96 Ru based on a measurement of absolute M 1, E1, and E2 transition strengths. Methods: Inelastic proton-scattering experiments have been performed at the Wright Nuclear Structure Laboratory (WNSL), Yale University, and the Institute for Nuclear Physics (IKP), University of Cologne. From the acquired proton-γ and γγ coincidence data we deduced spins of excited states, γ-decay branching ratios, and multipole mixing ratios, as well as lifetimes of excited states via the Doppler-shift attenuation method (DSAM). Results: Based on the new experimental data on absolute transition strengths, we identified the 2 + and 3 + members of the two-phonon mixed-symmetry quintuplet (2 + 1,ms ⊗ 2 + 1,s ). Furthermore, we observed strong M 1 transitions between low-lying 3 − and 4 + states suggesting one-phonon symmetric and mixed-symmetric octupole and hexadecapole components in their wave functions, respectively. The experimental results are compared to sdg-IBM-2 and shell-model calculations. Conclusions: Both, the sdg-IBM-2 and the shell-model calculations, are able to describe key features of mixed-symmetry excitations of 96 Ru. Moreover, they support the one-phonon mixedsymmetry hexadecapole assignment of the experimental 4 + 2 state.

Relativistic Coulomb excitation of Kr88

“…The existence of such a multiphonon structure with MS character was discovered in the nuclide 94 Mo [7,8] and can be explained by the F -spin symmetric O(6) limit of the IBM-2 [2]. Recent measurements on 94 Mo and other N = 52 isotones confirm [9][10][11][12][13][14][15] the initial findings as a general phenomenon [16]. Here, the evolution of MS states in N = 52 isotones can be tracked over different proton shells.…”

Shape coexistence and collective low-spin states in Sn112,114 studied with the (p,p′γSpieker1, Petkov2, Литвинова3 et al. 2018Phys. Rev. CSelf Cite180201View full textAdd to dashboardCite

“…For the case of the DSAM technique, these coincidence matrices can be determined unambiguously since the kinematics of the (p, p ′ γ) allow clear correlations, see, e.g., Refs. [15,20,22,23]. In total, there are three of such kinematically correlated DSA groups for excited states up to 4 MeV in 112,114 Sn when using the second SONIC version.…”

Combining γ-ray and particle spectroscopy with SONIC@HORUS

“…The detected γ-ray energy is then Doppler-shifted on an event-by-event basis depending on both the ejectile and γ-ray angles and energies. This shift can be used to extract lifetimes via the Doppler-Shift Attenuation Method as explained in [7], which has already been applied to several experiments [8][9][10].…”

“…By measuring the energy of the ejectile, nuclear level schemes can be studied in detail, since the excitation energy of the nucleus can be calculated from the ejectile energy. As presented in [7], the knowledge of the complete reaction kinematics also enables a precise and reliable determination of lifetimes using the Doppler-shift attenuation method (DSAM), which has already been applied for several experiments performed at SONIC@HORUS [8][9][10]. This paper will present the setup in more detail and will highlight a second main purpose of the setup: the determination of γdecay branching ratios, especially for high-lying lowspin states.…”