Description
Two reactions important for the CNO cycle break-out to rapid proton capture process in type I x-ray can profit from the
measurement of beta-delayed particle emission from GS of 20-Mg : 15-O(a,g)19-Ne and 19-Ne(p, g)20-Na.
19-Ne(p, g)20-Na : the resonance at Er = 457keV (E* = 2647keV in 20Na) in the Gamow window is populated by beta decay of 20-
Mg. From previous measurements, upper limits for the population of the state were reported and a lower limit for logft suggests that
the spin of the state has a value higher than 1.
15-O(a,g)19-Ne : following beta-proton decay, an excited state at 4.033 MeV in 19-Ne is populated. The astrophysical reaction is
dominated by a resonance at 4.03 MeV in 19-Ne at the temperatures of CNO-cycle break-out in type I x-ray bursts. The resonance
energy is known , but the strength is not measured. The observation in decay spectroscopy of an alpha branch from this state along
with the its known lifetime would allow to determine the resonance strength.
The most recent measurements of the beta decay of 20-Mg were done using a cocktail of fragmented 24Mg beam at NSCL and the
decaying nuclei were implated in a thick plastic detector. The production rate of 20-Mg was about 5kHz, and 20-Mg was about 35 %
out of the implanted cocktail-beam. Only beta and gamma emissions were measured.
Using SPIRAL1 20-Mg beam, DESIR purification facilities and DESIR Spectroscopy Decay station (with beta, gamma and charged
particle detection), one can provide a cleaner and more complete spectroscopy of 20-Mg decay.