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In a recent experiment performed at Triumf using the Dragon 0° spectrometer and its associated BGO array, the complete γ-decay of the radiative capture channel below the Coulomb barrier has been measured for the first time. This measurement has been performed at two energies Ec.m. = 6.6 and 7.2 MeV. A selective contribution of the entrance spins 2+ and 3- has been evidenced which is consistent with existing results above the barrier. [ABSTRACT FROM AUTHOR]

Reduced uncertainty in the thermonuclear rate of the 33S(p,γ)34Cl reaction would help to improve our understanding of nucleosynthesis in classical nova explosions. At present, models are generally in concordance with observations that nuclei up to roughly the calcium region may be produced in these explosive phenomena; better knowledge of this rate would help with the quantitative interpretation of nova observations over the S-Ca mass region, and contribute towards the firm establishment of a nucleosynthetic endpoint. As well, models find that the ejecta of nova explosions on massive oxygen-neon white dwarfs may contain as much as 150 times the solar abundance of 33S. This characteristic isotopic signature of a nova explosion could possibly be observed through the analysis of microscopic grains formed in the environment surrounding a nova and later embedded within primitive meteorites. An improved 33S(p,γ)34Cl rate (the principal destruction mechanism for 33S in novae) would help to ensure a robust model prediction for the amount of 33S that may be produced. Finally, constraining this rate could confirm or rule out the decay of an isomeric state of 34Cl (Ex = 146 keV, t1/2 = 32 m) as a source for observable gamma-rays from novae. We have performed several complementary experiments dedicated to improving our knowledge of the 33S(p,γ)34Cl rate, using both indirect methods (measurement of the 34S(3He,t)34Cl and 33S(3He,d)34Cl reactions with the Munich Q3D spectrograph) and direct methods (in normal kinematics at CENPA, University of Washington, and in inverse kinematics with the DRAGON recoil mass separator at TRIUMF). Our results will be used with nova models to facilitate comparisons of model predictions with present and future nova observables. [ABSTRACT FROM AUTHOR]

In a recent experiment performed at Triumf using the Dragon 0° spectrometer and its associated BGO array we have measured for the first time the full gamma decay of the radiative capture channel close to the Coulomb barrier. This measurement has been performed at 3 energies Ecm = 8.5, 8.8 and 9 MeV. We have extracted a radiative capture cross section more than five times larger than what had been previously observed. A selective contribution of the entrance spins 5- and 6+ has also been evidenced whereas 1- to 3- spins are predicted to be predominant by coupled-channel calculations. At Ecm = 9 MeV, stronger structural behaviour appears which is characterised by a larger total cross section and also by the particularly strong feeding of the 28Si prolate 4+ state at 9.16 MeV. This level is explained by several models in terms of 12C-16O cluster sub-structure. Our data is compared to such cluster-model predictions and the agreement is quite good. [ABSTRACT FROM AUTHOR]

The 12C(16O,γ)28Si radiative capture reaction has been studied at energies close to the Coulomb barrier at Triumf (Vancouver) using the Dragon spectrometer and its associated BGO array. It has been observed that the γ decay flux proceeds mainly via states around 10–11 MeV and via the direct feeding of the 28Si 31- (6879 keV) and 42+ (6888 keV) deformed states. A discussion is presented about this selective feeding as well as perspectives for the use of novel detection systems for the study of light heavy-ion radiative capture reactions. [ABSTRACT FROM AUTHOR]

The heavy-ion radiative capture reactions 12C(12C,γ)24Mg and 12C(16O,γ)28Si have been performed on and off resonance at TRIUMF using the Dragon separator and its associated BGO array. The decay of the studied narrow resonances has been shown to proceed predominantly through quasi-bound doorway states which cluster and deformed configurations would have a large overlap with the entry resonance states. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Resonances in the 12C(16O,γ)28Si radiative capture process at energies around the Coulomb barrier have been probed using the very selective 0° Dragon spectrometer at Triumf and its associated BGO γ-array. For the first time the full level scheme involved in this process has been measured and shows previously unobserved γ-decay to doorway states around 11 MeV in 28Si. [ABSTRACT FROM AUTHOR]