L. Donadille

4 He Decay of Excited States in 14 C

A study of the 7Li(9Be,4He 10Be)2H reaction at E{beam}=70 MeV has been performed using resonant particle spectroscopy techniques and provides the first measurements of alpha-decaying states in 14C. Excited states are observed at 14.7, 15.5, 16.4, 18.5, 19.8, 20.6, 21.4, 22.4 and 24.0 MeV. The experimental technique was able to resolve decays to the various particle bound states in 10Be, and provides evidence for the preferential decay of the high energy excited states into states in 10Be at ~6 MeV. The decay processes are used to indicate the possible cluster structure of the 14C excited states.

α-decay of excited states in 11C and 11B

Abstract Studies of the 16O(9Be, α7Be)14C and 7Li(9Be, α7Li)5He reactions at E beam = 70 MeV have been performed using resonant particle spectroscopy techniques. The 11C excited states decaying into α + Be 7 ( gs ) are observed at 8.65, 9.85, 10.7 and 12.1 MeV as well as possible states at 12.6 and 13.4 MeV. This result is the first observation of α-decay for excited states above 9 MeV. The α + Li 7 ( gs ) decay of 11B excited states at 9.2, 10.3, 10.55, 11.2, (11.4), 11.8, 12.5, (13.0), 13.1, (14.0), 14.35, (17.4) and (18.6) MeV is observed. The decay processes are used to indicate the possible three-centre 2 α + He 3 ( H 3 ) cluster structure of observed states. Two rotational bands corresponding to very deformed structures are suggested for the positive-parity states. Excitations of some observed T = 1 / 2 resonances coincide with the energies of T = 3 / 2 states which are the isobaric analogs of the lowest 11Be states. Some of these states may have mixed isospin.

Search for molecular states in 16C

In order to search for a proposed α:2n:α:2n:α molecular structure in 16C its break-up into 10Be + 6He, 12Be + α, 8He + 2α and 6He + 6He + α has been studied using a 560 MeV 16C beam inelastically excited on a 12C target. States in 16C appear to be only weakly populated in this reaction.

Three-centre cluster structure in 11C and 11B

Studies of the 16O(9Be,α7Be)14C, 7Li(9Be,α7Li)5He and 7Li(9Be,ααt)5He reactions at Ebeam = 70 and 55 MeV have been performed using resonant particle spectroscopy techniques. The 11C excited states decaying into α + 7Be(gs) are observed between 8.5 and 13.5 MeV. The α + 7Li(gs), α + 7Li* (4.652 MeV) and t+8Be(gs) decays of 11B excited states between 9 and 19 MeV are observed. The decay processes are used to indicate the possible three-centre 2α + 3He (2α + 3H) cluster structure of observed states. This cluster structure is more prominent in the positive-parity states, where two rotational bands with large deformations are suggested. Excitations of some of the observed T = 1/2 resonances coincide with the energies of previously measured T = 3/2 isobaric analogues of the 11Be states, indicating that these states may have mixed isospin.

Experimental evidence for cluster structure of 11B excited states

The kinematically complete measurements of the 7Li(9Be,ααt)5He reaction at Ebeam = 55 and 70 MeV have been performed and the reconstructed 11B excitation energy spectra were compared with the 7Li(9Be,α7Li)5He results obtained at the same beam energies. Evidence was found for the t+8Be(g.s.) decay of the 11B excited states at 13.1 and 14.4 MeV, the α+7Li*(4.652 MeV) decay of the states at 14.4 and 17.5 MeV and for the t+8Be*(3.03 MeV) decay of the 17.5 MeV state in 11B. A study of the relative yields for the decay of the 14.4 MeV state indicates that significant part of α‐decay strength goes into the 2α+t three‐body decay channel.

alpha-decay of excited states in 11C and 11B

Abstract Studies of the 16O(9Be, α7Be)14C and 7Li(9Be, α7Li)5He reactions at E beam = 70 MeV have been performed using resonant particle spectroscopy techniques. The 11C excited states decaying into α + Be 7 ( gs ) are observed at 8.65, 9.85, 10.7 and 12.1 MeV as well as possible states at 12.6 and 13.4 MeV. This result is the first observation of α-decay for excited states above 9 MeV. The α + Li 7 ( gs ) decay of 11B excited states at 9.2, 10.3, 10.55, 11.2, (11.4), 11.8, 12.5, (13.0), 13.1, (14.0), 14.35, (17.4) and (18.6) MeV is observed. The decay processes are used to indicate the possible three-centre 2 α + He 3 ( H 3 ) cluster structure of observed states. Two rotational bands corresponding to very deformed structures are suggested for the positive-parity states. Excitations of some observed T = 1 / 2 resonances coincide with the energies of T = 3 / 2 states which are the isobaric analogs of the lowest 11Be states. Some of these states may have mixed isospin.

alpha-decay of excited states in C-11 and B-11

Abstract Studies of the 16O(9Be, α7Be)14C and 7Li(9Be, α7Li)5He reactions at E beam = 70 MeV have been performed using resonant particle spectroscopy techniques. The 11C excited states decaying into α + Be 7 ( gs ) are observed at 8.65, 9.85, 10.7 and 12.1 MeV as well as possible states at 12.6 and 13.4 MeV. This result is the first observation of α-decay for excited states above 9 MeV. The α + Li 7 ( gs ) decay of 11B excited states at 9.2, 10.3, 10.55, 11.2, (11.4), 11.8, 12.5, (13.0), 13.1, (14.0), 14.35, (17.4) and (18.6) MeV is observed. The decay processes are used to indicate the possible three-centre 2 α + He 3 ( H 3 ) cluster structure of observed states. Two rotational bands corresponding to very deformed structures are suggested for the positive-parity states. Excitations of some observed T = 1 / 2 resonances coincide with the energies of T = 3 / 2 states which are the isobaric analogs of the lowest 11Be states. Some of these states may have mixed isospin.