H G Price

Quasi-band structure in 64Zn

The reactions 61Ni( alpha ,n gamma )64Zn and 56Fe(11B,2pn gamma )64Zn have been used to make spin assignments of Jpi =6+,6+ and 7- to the levels in 64Zn at 3994, 4237 and 4636 keV respectively. Lifetime measurements of 175+or-50 fs and 190+or-60 fs for the two Jpi =6+ levels yield E2 transition strengths of 23+or-5 Wu for the 61+ to 41+ transition and 37-9+17 Wu for the 62+ to 42+ transition. These results indicate the presence of two quasi-bands in 64Zn.

Gamma-ray studies in 64Zn: levels above 3.1 MeV

The 61Ni ( alpha ,n gamma ) 64Zn reaction has been studied 8.6 MeV and 9.35 MeV bombarding energies together with the 56Fe(11B, p2n gamma )64Zn reaction at 30 MeV bombarding energy. The gamma -ray decay scheme of 64Zn has been deduced up to 5.7 MeV excitation by means of gamma - gamma coincidence experiments and n- gamma coincidence experiments. Spins and parities have been deduced for most of the high-spin states between 3.1 and 5.7 MeV excitation by means of gamma -ray angular distribution measurements together with gamma -ray linear polarisation measurements. The lifetimes of levels have been measured by DSAM enabling electromagnetic transition rates to be determined for many transitions. The results have been compared with shell-model, cluster-vibration model and interacting boson approximation calculations.

Gamma ray spectroscopy in 64Zn-levels below 3.1 MeV in excitation

States in 64Zn were populated using the 61Ni( alpha ,n gamma )64Zn reaction at a beam energy of 7.8 MeV. Excitation energies, gamma ray branching ratios, angular distributions, linear polarisations and centroid shifts were measured for levels in 64Zn below 3.1 MeV in excitation. Electromagnetic multipole mixing ratios were determined for many of the gamma ray transitions. New spin and parity assignments of Jpi =3+ and 2+ have been made for the levels at 2979 keV and 3005 keV, whilst the spins and parities of the 2737, 2794 and 3078 keV levels are confirmed at 4+, 2+ and 4+ respectively. The spin and parity of the 3093 keV level has been restricted to either 3+ or 2+.

Heavy-ion gamma-ray spectroscopy of 60Ni

Twenty excited states below 6.8 MeV and with spins up to J=(9) have been observed in 60Ni in the reaction 56Fe(7Li, p2n gamma ). Lifetimes of levels have been determined from DSA and RD measurements. Gamma-ray angular distribution and linear polarisation measurements have been made and unambiguous Jpi assignments deduced. Several new high-spin states above 4 MeV in excitation are proposed and the results have been compared with the predictions for high-spin states of various theoretical models.

Gamma-ray spectroscopy on 48Cr

High-spin states in 48Cr have been investigated with the 36Ar(14N,pn gamma )48Cr and 40Ca(10B,pn gamma )48Cr reactions. Mean lifetimes or limits have been obtained for the following levels: 0.75 MeV (10.6+or-1.1 ps), 1.86 MeV (1.9+or-0.5 ps), 3.45 MeV (<1.0 ps), 3.53 MeV (3.6+or-1.0 ns), 4.06 MeV (40+or-10 ps) and 5.19 MeV (<1.2 ps). New spin-parity assignments have been made for the last four levels: 6+, 5(-), 6(-), and (8)+, respectively. Comparisons are made with simple shell-model calculations.

A study of the neutron-deficient isotope 66Ge

The neutron-deficient isotope 66Ge has been studied using gamma-ray spectroscopy techniques. States in 66Ge were populated using the 58Ni(10B,pn gamma )66Ge reaction at bombarding energies of 28.5, 29 and 30 MeV. A decay scheme has been established from the results of gamma-gamma and neutron-gamma coincidence experiments performed at a beam energy of 28.5 MeV. Angular distributions were measured at beam energies of 28.5, 29 and 30 MeV, and linear polarisations were measured at 28.5 MeV. The analysis of these data yields spin-parity assignments of 1694 keV (2+), 2175 keV (4+), 3686 keV (4+,5-), 4208 keV (6+,7-) and a probable 6+ assignment to the 3657 keV level. Spin restrictions are also placed on several other levels. The lifetimes of the 958, 1694 and 4208 keV levels are deduced from a recoil-distance-method experiment, performed at a beam energy of 29 MeV, to be 5.3+or-1.0 ps, 6.5+or-2.5 ps and 295+or-40 ps respectively. A limit of less than 3 ps has also been placed on the lifetime of the 2175 keV level.

Further evidence for particle-vibration coupling among the positive parity states of 65,67Zn

The structures of the nuclei 65,67Zn have been investigated by the techniques of gamma -ray spectroscopy in conjunction with the reactions 62,64Ni( alpha ,n)65,67Zn. Gamma-gamma coincidence measurements and yield curve measurements have been used to elucidate the decay schemes. Measurements of gamma -ray angular distributions and linear polarizations have been used to determine mixing ratios for the decays of several levels in both nuclei and to make spin assignments to the following levels in 65Zn: 1.958 (7/2+), 2.054 (13/2+), 2.135 (9/2+), 2.138 (11/2+) and in 67Zn: 0.979 (5/2+), 1.603 (7/2+), 1.640 (13/2+), 1.732 (11/2+), 1.782 (3/2,5/2)+, 1.807 (9/2+). Lifetime measurements have been made using the Doppler-shift attenuation method, and electromagnetic multipole transition strengths have been deduced. The data provide further evidence for the existence of particle-vibration coupling in this mass region.

Gamma ray spectroscopy in 61Ni-levels below 2.2 MeV in excitation

States in 61Ni were populated using the 58Fe( alpha ,n gamma )61Ni and the 53Cr(11B,p2n gamma )61Ni reactions. Gamma-gamma coincidence measurements at alpha particle energies of 8.0, 8.5 and 12.0 MeV and at a 11B energy of 30 MeV were used to determine the decay scheme. Excitation energies, gamma ray branching ratios, angular distributions, linear polarizations and mixing ratios for levels above 2.2 MeV in excitation were measured at alpha particle energies of 11.0 and 13.0 MeV. The analysis of the angular distributions and linear polarizations yielded spin and parity assignments. Electromagnetic multipole mixing ratios were determined for several of the gamma ray transitions. Centroid shifts were extracted from the 11 MeV angular distribution data. The mean lifetimes of the 2409, 3259, 3298 and the 3435 keV levels were deduced.

States in 89Sr excited by the 86Kr(α, n)89Sr reaction

Abstract The reaction 86 Kr(α, n) with E α = 12−16 MeV was used to populate excited states in 89 Sr. The de-excitation of these states was studied by in-beam γ-ray spectroscopy. DSA lifetime measurements were performed using a solid gas target. A number of new high-spin states was found, and lifetimes of ten states were obtained. Some of the states are discussed within the framework of a particle-anharmonic vibrator model.

Gamma-ray spectroscopy in 63Zn and 63Cu

Electromagnetic decay transitions in 63Zn and 63Cu have been studied using the 60Ni( alpha ,n gamma )63Zn and 60Ni( alpha ,p gamma )63Cu reactions at incident beam energies of 9.5-19.0 MeV, the 54Fe(11B,np gamma )63Zn and 54Fe(11B,2p gamma )63Cu reactions at EB=30.0 MeV, and the 58Ni(7Li,pn gamma )63Zn reaction at ELi=20.0 MeV. Gamma-gamma coincidence measurements have been used to determine the decay schemes. Spins and parities of the levels together with branching and mixing ratios of the gamma -ray transitions have been deduced from angular distribution and linear polarisation measurements. Mean lifetimes of the 193, 248, 1704 and 2585 keV levels in 63Zn have been obtained using the recoil-distance method (RDM). Lifetimes of many levels in 63Zn and 63Cu have been deduced from the Doppler-shift attenuation method (DSAM). The results are discussed in terms of the shell model and the intermediate coupling model.