Nuclear structure of odd-oddY82

Abstract

Excited states in Y have been investigated via the Ni( Si, 3pn) Y and Fe( Si,p2n) Y reactions using beams provided by the Florida State University Tandem-LINAC with energies of 95 to 135 MeV. Particle-p coincidences with a full-sphere charged-particle detector and an excitation curve were used to assign p rays to Y. The Fe( Si,p2n) Y reaction at 95 MeV was used to measure p-p coincidences with five Compton-suppressed Ge detectors, Lifetimes in the ns and ps ranges were measured using direct timing and the Doppler-shift attenuation method. A level scheme with 39 states was constructed up to tentative spins and parities of (15 ) and (21+). In the positive-parity yrast band a phase reversal was observed in the signature splitting at I = 105. The B(M1) strengths in this band alternate with signature between about 0.1 and 1.0 p~. The B(E2) strengths of about 90 Weisskopf units are in good agreement with those predicted by Hartree-Fock-Bogolyubov calculations. Particle-rotor calculations indicate a prolate or triaxial core shape for the positive-parity band. PACS number(s):

Collective excitations and shape changes inY80

“…For the most part, many of these behaviors can be explained from a theoretical standpoint (see Refs. [3][4][5]). For example, the 2-qp plus rotor model [6] has demonstrated good qualitative agreement with the observed alternations in the normalized energy differences (signature splitting pattern) and the B͑M1͒ strengths with spin in 82 Y [4] and 78 Rb [7].…”

Rotational structures in the odd-odd nucleus80Y

“…They look very similar to the yrast positive parity structure observed in s=y [2][3][4]; based on this close similarity we have assigned, tentatively, the spin values shown in Fig.1 for these two bands (above the state with spin 8 in band 1). The other spin values given in the figure are also tentative, and are based on DCO ratio values deduced from the coincidences between the detector rings at 900 and at 360 and 1440 , respectively.…”

“…[1][2][3][4]): a large signature splitting and a possible signature inversion around spin 9, as expected for a transition from particle realignment to collective rotation. There is also an irregularity in both the static and dynamic moment of inertia of these bands at a frequency of hw ~0.75 MeV, which probably has the same nature with that observed in s~y at hw ~0.65 MeV [3].…”

“…Very little is known about the odd-odd ones, where the neutron-proton interaction between particles in the same shells should be particularly important. High spin states in the odd-odd neutron deficient Y isotopes became available only recently for say [1] and s=y [2][3][4], while nothing is known about the level scheme of soy. Published information on this nucleus mentions two gamma rays, of 267 and 289 keV, respectively, which presumably deexcite states of relatively high spin in this nucleus [5].…”

Coexisting single-particle and collective excitations inAs70

“…The strong alternations observed in the B(M1) strengths for both nuclei are consistent in phase and magnitude with those of other odd-odd nuclei in this mass region [11]. They have been understood within the context of both the interacting boson-fermion approximation [35] and the twoqp-plus-rotor coupling model [36] in terms of how the odd particles couple to the core spin.…”