Clarification of the Three-Body Decay of 12C (12.71 MeV)

Using β decays of a clean source of 12 N produced at the IGISOL facility, we have measured the breakup of the 12 C (12.71 MeV) state into three α particles with a segmented particle detector setup. The high quality of the data permits solving the question of the breakup mechanism of the 12.71 MeV state, a longstanding problem in few-body nuclear physics. Among existing models, a modified sequential model fits the data best, but systematic deviations indicate that a three-body description is needed

Projectile Coulomb excitation with fast radioactive beams

5 pages, 5 figures, 1 table.-- PACS nrs.: 23.20.Ck; 27.20.+n.We report a search for γ rays emanating from Coulomb excitation of fast (30-46 MeV/u) radioactive projectiles He-8, Be-11, Be-12, Be-14 interacting with a lead target. These are clearly identified by their Doppler shift. The 320 keV 1/2(-) --> 1/2(+)γ transition from Be-11 was observed with a cross-section of 191 ± 26 mb which is noticeably less than expected from the known lifetime and in the perturbation limit of pure Coulomb excitation. In the other nuclei rather stringent upper limits of 0.01 to 0.2 Weisskopf units, are placed on the hypothetical transition to 1(-) states.We would like to thank F. Geoffroy, R. Hue and L. Petizon for their technical assistance during the experiment, N. Alamanos, G. Baur aud C. Bertulani for discussions and R. Lombard for drawing our attention to the Bertlmann-Martin bound. This work was partly supported by la Région Basse Normandie. One of us, G. Schrieder, would like to thank for the support by the German Federal Minister for Research and Technology (BMFT) under contract 06DA641.Peer reviewe

Study of charged particles emitted in the β\beta-decay of 6,8^{6,8}He

The beta-delayed charged particle spectra from He-6 and He-8 were measured with a telescope consisting of a gas counter and a Si surface barrier detector. Beta-delayed deuterons and tritons are emitted in the two cases with branching ratios of (7.6 +/- 0.6) x 10(-6), E(d) > 350 keV and (8.0 +/- 0.5) x 10(-3), respectively. Both spectra present anomalies that must be due to the special structure of these nuclei (an alpha core surrounded by several neutrons)

Study of Charged-Particles Emitted in the Beta-Decay of He-6,He-8

The beta-delayed charged particle spectra from He-6 and He-8 were measured with a telescope consisting of a gas counter and a Si surface barrier detector. Beta-delayed deuterons and tritons are emitted in the two cases with branching ratios of (7.6 +/- 0.6) x 10(-6), E(d) > 350 keV and (8.0 +/- 0.5) x 10(-3), respectively. Both spectra present anomalies that must be due to the special structure of these nuclei (an alpha core surrounded by several neutrons)

Clarification of the three-body decay of C-12 (12.71 MeV)

4 pages, 2 figures.--PACS nrs.: 21.45.+v; 23.40.–s; 27.20.+n.Using beta decays of a clean source of N-13 produced at the IGISOL facility, we have measured the breakup of the C-12 (12.71 MeV) state into three alpha particles with a segmented particle detector setup. The high quality of the data permits solving the question of the breakup mechanism of the 12.71 MeV state, a longstanding problem in few-body nuclear physics. Among existing models, a modified sequential model fits the data best, but systematic deviations indicate that a three-body description is needed.This research was supported by the Academy of Finland under the Finnish Centre of Excellence Programme 2000-2005 (Project No. 44875, Nuclear and Condensed Matter Physics Programme at JYFL), by the Spanish Agency CICYT under Contract No. AEN99-1046-C02-02, and by the European Union Fifth Framework Programme ‘‘Improving Human Potential–Access to Research Infrastructure.’’Peer reviewe