S.C. Allcock

Symmetric fission of 24Mg following inelastic scattering

Abstract Symmetric fission into two 12 C nuclei has been observed from states at high excitation energy in 24 Mg excited in inelastic scattering. Fission to the 10 B+ 4 N channel has also been observed and indirect evidence for the 16 O+ 8 Be channel noted. The same experiment also reveals fission into 16 O+ 12 C from states in 28 Si populated by alpha-particle pickup onto the 24 Mg projectile. The correlation of the states in 24 Mg observed in this experiment with those previously observed in 12 C+ 12 C scattering is discussed.

A study of 19F by inelastic scattering on a 12C target at 82 MeV and 144 MeV using the techniques of resonant particle spectroscopy

Abstract The α-decay of states in 19F has been studied in the sequential breakup reaction 12 C ( 19 F , 19 F ∗ → 15 N α) at laboratory energies of 82 and 144 MeV. Double differential cross sections have been obtained for 20 excited states in 19F. The correlations show a systematic dependence on the reaction angle θ c.m. ∗ which allows the transferred angular momentum to be deduced. Using this result we present evidence for two new states (J π = 5 2 − or 7 2 − ) at excitation energies of 7740 keV and 8277 keV and two parity assignments for states at 7245 keV ( 3 2 + ) and 9287 keV ( 7 2 + , 9 2 + ) . Comparisons with shell model calculations suggest the two new states probably have J π = 5 2 − and 7 2 − respectively. The double differential cross sections have been analysed with a strong absorption model which allows extraction of qualitative information on the reaction mechanism.

10+ states in 20Ne

Abstract The α-transfer reaction 12C(16O, 20Ne∗)8Be has been studied at a bombarding energy of 150 MeV in a search for high-spin α-cluster resonances in 20Ne. Angular correlations were measured for states in 20Ne which α-decay to the ground state of 16O. A broad 10+ resonance was located at E x ( 20 Ne )∼27.5 MeV , but no definite evidence was found for any 10+ strength at lower excitation energy.

High-spin α-cluster resonances in 16O

Abstract The α-transfer reaction 12 C( 12 C, 16 O ∗ ) 8 Be has been studied at E lab =120 MeV in a search for high-spin resonances in 16 O. Coincidence techniques were used to measure the α 0 and α 1 decaychannels leading respectively to the ground and first excited states of 12 C. A 9 − resonance with a significant width for α 1 decay has been found at E x ∼30 MeV in 16 O; the 16 O; the α 0 correlation is anomalous but can be fitted by a coherent mixture of L =8 and L =9 transfer components. These results are compared with recent cluster model calculations and α particle elastic scattering data.

Symmetric and near-symmetric fission of 24Mg, 28Si and 32S

Abstract In several recent measurements the symmetric fission of 24 Mg has been reported. In this paper the results of a search for similar processes in 28 Si and 32 S are presented. In contrast to the results for 24 Mg, no evidence is seen for the fission of 28 Si to 16 O+ 12 C or 32 S to 16 O+ 16 O following inelastic excitation. However, these processes are observed to occur following pickup onto 24 Mg. The results are consistent with a simple model of the fission process developed by Harvey and suggest the existence of large scale cluster structure in all three nuclei.

Spins of 12C + 12C resonances via the 12C(12C, αα)16O reaction

Abstract We have measured the spins of 12 C + 12 C resonances which decay to the ground state of 16 O via excited states of 20 Ne using a novel α-α angular correlation geometry. Between E CM = 19 and 27 MeV we find that spins of 12 and 14 dominate many of the resonant cross sections. We observe qualitatively different results for α-decays via the low lying bands in 20 Ne and those which proceed via the 18.54 MeV 8 + state in 20 Ne. We interpret our results in terms of Nilsson Strutinsky calculations and recent α-cluster model calculations for 24 Mg.

A compact high-efficiency 8Be detector

Abstract We report the operation and performance of a compact, high-efficiency 8Be detector designed for use in breakup reaction studies. It offers a number of advantages over previous detectors in allowing accurate kinematical identification of 8Be excited states and scattering angle as well as allowing large solid angle coverage.

16O+8Be breakup of 24Mg

Abstract 16O+8Be breakup of 24Mg has been identified following inelastic scattering of 24Mg projectiles. The spectrum of states observed is compared to that previously measured in the 12C+12C breakup channel to obtain information on the partial decay widths.

Spin assignments for states in 20Ne via the 12C(16O, 20Ne∗)8Be transfer reaction

Abstract The α-transfer reaction 12 C( 16 O, 20 Ne∗) 8 Be has been studied at E lab = 150 MeV. The 16 Oα angular correlations from the decay of 20 Ne∗ have been measured and analysed with a strong absorption model to make spin assignments for many high-spin states at high excitation in 20 Ne.