High spin states inTc93

Abstract

High spin states in the N =50 nucleus Tc were populated and studied using the reaction Zn ( 'P, 2p2n) Tc at a beam energy of 115 MeV. Gamma ray intensities and gamma-gamma coincidences were measured. Multipolarities of the transitions were extracted assuming stretched transitions. The positive and negative parity bands have been extended up to spins '2 + and 2, respectively. The proposed level scheme above J = 2 cannot be well understood on the basis of the spherical shell model calculations with valence protons occupying the (1f,/2, 2p3/2 2p, /2, 1g9/2) configuration space. The breaking of the N =50 neutron core appears to be a plausible mechanism for the observed high spin states.PACS number(s): 23.20.Lv, 23.20.En, 21.60.Cs, 27.60.+j

Shell model study of high spin states in theN=50 nucleus93Tc

“…Two of these gamma rays 2484 and 2164 keV were found to be in-band transitions belonging to the negative parity band. Their multipolarity assignments were made by using the procedure described in [2,3]. The 2484 keV gamma ray was found to be M1 in character, whereas the 2164 keV gamma ray was found to be E2 in character.…”

“…The proposed level scheme above J= 25/2 could not be well understood on basis of the spherical shell model calculations, with the valence protons occupying the {0f5/2, lp3/2 , lp~/2, 0g9/2} configuration space outside 66Ni as a core. In the paper [2] mentioned above, we remarked that breaking of the N= 50 neutron core seemed a plausible mechanism to understand the observed high spin states in 93Tc. However the breaking of the neutron core requires the excitation of a neutron from Og9/2 orbit into the 1 ds/2 orbit.…”

“…We have recently reported [2] our study of high spin states in 93Tc using the reaction 66Zn (31p, 2p 2n) 93Tc at a beam energy of ll5MeV. The positive and negative parity bands were extended upto spins of 39/2 + and 43/2-respectively.…”

“…This energy gap is reduced to about 2 MeV in this mass region due to many body correlations [2]. To specifically look for these 2 MeV y rays, a separate experiment was conducted by setting the amplifier gains low enough so as to have a dynamic energy range of 50 keV to 2700 keV.…”

“…The 35C1 beam was provided by the 15 UD Pelletron Accelerator at the Nuclear Science Centre (NSC), New Delhi. y-y coincidences were measured using the Gamma Detector Array (GDA) at the NSC, comprising of 5 Compton suppressed germanium detectors and a 14 element BGO multiplicity filter [2]. About 30 million multi-parameter events corresponding to two or higher fold coincidences, within a system timing resolution of 40 ns, were recorded in list mode.…”