"Superdeformation and clustering in 24Mg and 28Si"
David Jenkins , Department of Physics, University of York, York
(id #204)
Seminar: NoPoster: No
Invited talk: Yes
David Jenkins1, P. Marley1, C.J. Lister2, F. Haas3, S. Courtin3 and D. Lebhertz3
1 Department of Physics, University of York, York YO10 5DD, UK
2Physics Division, Argonne National Laboratory
3IPHC, Universite Louis Pasteur, F-67037 Strasbourg, France
Taniguchi et al. have recently performed antisymmetrized molecular dynamics (AMD) calculations for 28Si and delineate a range of excited, highly-deformed configurations based on 12C+16O and 24Mg+4He clustering [1]. The latter configuration is associated with the superdeformed band predicted for 28Si. Similar structures are also expected in 24Mg based on 12C+12C clustering. The increasing sophistication of these calculations, which predict both the parentage of these different configurations as well as the strength of in-band transitions, prompts a renewed experimental search for possible candidate states. A review of possible candidates for cluster states in 28Si found in the literature will be given. We will also present new information on gamma-decaying, excited states in 28Si taken from a study of the 12C(20Ne,)28Si reaction using the Gammasphere array at Argonne National Laboratory (ANL).The predicted structure of the cluster states in 24Mg and 28Si suggests that alpha- or heavy-ion radiative capture may be a promising strategy in attempting to locate cluster configurations experimentally. Comparatively little is known about the latter process of heavy-ion radiative capture (HIRC), which is difficult to study due to the large positive Q-values and the overwhelming competition from particle emission. Sandorfi found a series of narrow resonances on and around the Coulomb barrier in the 12C(12C,) and 12C(16O,) reactions in the late 1980s [2]. We have revisited the topic of heavy ion radiative capture, by searching for a doorway mechanism whereby the capture decay would favorably populate high-lying states with a larger structural overlap with the entry resonance. In this manner, it might be possible to locate the superdeformed band in 24Mg, whose band-head is predicted to lie around 10 MeV, by feeding it from above. Three known resonances in the 12C(12C,) reaction at Ec.m=6.0, 6.7 and 8.0 MeV have been studied using the combination of the DRAGON recoil separator and BGO array at TRIUMF [3]. This has allowed firm spin assignments to be made to the resonances and for the general character of the HIRC process to be understood. We have recently carried out a more detailed study of the 12C(12C,) reaction at Ec.m=8.0 MeV using the Gammasphere array and Fragment Mass Analyser at ANL. This shows many interesting aspects relating to non-statistical decay branching including a strong decay to a K=0− band and a number of states around 10 MeV in 24Mg. Preliminary results from this experiment will be presented. We acknowledge the contribution of many other colleagues to the successful running of the Gammasphere and DRAGON experiments.
1 Department of Physics, University of York, York YO10 5DD, UK
2Physics Division, Argonne National Laboratory
3IPHC, Universite Louis Pasteur, F-67037 Strasbourg, France
Taniguchi et al. have recently performed antisymmetrized molecular dynamics (AMD) calculations for 28Si and delineate a range of excited, highly-deformed configurations based on 12C+16O and 24Mg+4He clustering [1]. The latter configuration is associated with the superdeformed band predicted for 28Si. Similar structures are also expected in 24Mg based on 12C+12C clustering. The increasing sophistication of these calculations, which predict both the parentage of these different configurations as well as the strength of in-band transitions, prompts a renewed experimental search for possible candidate states. A review of possible candidates for cluster states in 28Si found in the literature will be given. We will also present new information on gamma-decaying, excited states in 28Si taken from a study of the 12C(20Ne,)28Si reaction using the Gammasphere array at Argonne National Laboratory (ANL).The predicted structure of the cluster states in 24Mg and 28Si suggests that alpha- or heavy-ion radiative capture may be a promising strategy in attempting to locate cluster configurations experimentally. Comparatively little is known about the latter process of heavy-ion radiative capture (HIRC), which is difficult to study due to the large positive Q-values and the overwhelming competition from particle emission. Sandorfi found a series of narrow resonances on and around the Coulomb barrier in the 12C(12C,) and 12C(16O,) reactions in the late 1980s [2]. We have revisited the topic of heavy ion radiative capture, by searching for a doorway mechanism whereby the capture decay would favorably populate high-lying states with a larger structural overlap with the entry resonance. In this manner, it might be possible to locate the superdeformed band in 24Mg, whose band-head is predicted to lie around 10 MeV, by feeding it from above. Three known resonances in the 12C(12C,) reaction at Ec.m=6.0, 6.7 and 8.0 MeV have been studied using the combination of the DRAGON recoil separator and BGO array at TRIUMF [3]. This has allowed firm spin assignments to be made to the resonances and for the general character of the HIRC process to be understood. We have recently carried out a more detailed study of the 12C(12C,) reaction at Ec.m=8.0 MeV using the Gammasphere array and Fragment Mass Analyser at ANL. This shows many interesting aspects relating to non-statistical decay branching including a strong decay to a K=0− band and a number of states around 10 MeV in 24Mg. Preliminary results from this experiment will be presented. We acknowledge the contribution of many other colleagues to the successful running of the Gammasphere and DRAGON experiments.
