Multiphonon states in56136Ba80

Abstract

Low-lying multiphonon states in 136 Ba have been populated with the inelastic neutron scattering reaction. Excitation functions were performed at neutron energies from 2.2 to 3.9 MeV, and γ -ray angular distributions were measured at 2.5, 3.0, and 3.5 MeV. Lifetimes have been determined using the Doppler-shift attenuation method, and electromagnetic transition rates have been deduced. The previously assigned 2 + 1,ms mixed-symmetry state at 2128.9 keV has been confirmed and is not greatly fragmented. For the first time in the N = 80 isotones, a 3 + 2,ms two-phonon mixed-symmetry state is proposed. In addition, the 2 + 5 and the 4 + 3 levels at 2222.7 and 2356.4 keV, respectively, decay with large B(M1) values to the two-phonon 2 + 2 and 4 + 1 states, respectively, which suggests two-phonon mixed-symmetric character. Their excitation energies, however, are not consistent with this interpretation.

Decay of quadrupole-octupole1−states inCa40andCe140Derya1, Tsoneva2, Aumann3 et al. 2016Phys. Rev. C12120View full textAdd to dashboardCite

“…It is interpreted as a pure isoscalar oscillation which is predicted in all Ca isotopes [79] and was experimentally identified in 40 Ca and 48 Ca [14]. The quadrupoleoctupole two-phonon candidate which is investigated in the present work, is the 1 (2) mW.u.…”

“…Low-lying E1 excitations have been studied systematically in 40 Ca, 44 Ca, and 48 Ca by means of NRF experiments [14,63,[75][76][77]. The doubly-magic N = Z nucleus 40 Ca exhibits almost no low-lying E1 strength, whereas 44 Ca and 48 Ca exhaust more and a similar amount of the Thomas-Reiche-Kuhn energy-weighted sum rule [76,77].…”

“…In the present experiments the bandwidth of the photon beam amounted to 4%. The 140 Ce target was composed of 2 g highly enriched (99.72%) plus 7.5 g natural ceriumoxide powder, whereas for the 40 Ca experiment an 11.2 g natural calcium-carbonate target was used. Both measurements were carried out for about 23 h, each.…”

“…Real-photon scattering ( γ, γ) experiments were performed to study the γ-decay behavior of possible twophonon J π = 1 − states in 40 Ca and 140 Ce. The states of interest were populated by the quasi-monochromatic, linearly polarized, and intense beam of real photons provided at the High Intensity γ-ray Source (HIγS) facility [60,61] at the Triangle Universities Nuclear Laboratory (TUNL) in Durham, NC, USA.…”

“…The collective quadrupole and oc-tupole excitations of electric character are usually among the lowest-lying excitations in nuclei in the vicinity of shell closures. They are interpreted as surface oscillations and theoretically treated as phonons with the possibility to couple to multi-phonon states, like for example double-quadrupole or double-octupole states [37][38][39][40]. The mixed harmonic coupling of quadrupole and octupole collective phonons (2…”