β-delayed γ decay of 20Mg and the Ne 19 ( p , γ ) 20 Na breakout reaction in Type I X-ray bursts

Glassman, B. E.; Pérez-Loureiro, D.; Wrede, C.; Allen, J.; Bardayan, D. W.; Bennett, M. B.; Brown, B. A.; Chipps, K. A.; Febbraro, M.; Friedman, M.; Fry, C.; Hall, M. R.; Hall, O.; Liddick, S. N.; O'Malley, P.; Ong, W. J.; Pain, S. D.; Prokop, C.; Schwartz, S. B.; Shidling, P.; Sims, H.; Thompson, P.; Zhang, H.

doi:10.1016/j.physletb.2018.01.041

Title: β-delayed γ decay of 20Mg and the ${}^{19}{Ne} {(p, γ)}^{20} Na$ breakout reaction in Type I X-ray bursts

Journal Article · Thu Mar 01 00:00:00 EST 2018 · Physics Letters B

DOI:https://doi.org/10.1016/j.physletb.2018.01.041· OSTI ID:1437815

Glassman, B. E.;

; Wrede, C.; Allen, J.; Bardayan, D. W.; Bennett, M. B.; Brown, B. A.; Chipps, K. A.; Febbraro, M.; Friedman, M.; Fry, C.; Hall, M. R.; Hall, O.; Liddick, S. N.; O'Malley, P.; Ong, W. J.; Pain, S. D.; Prokop, C.; Schwartz, S. B.; Shidling, P. more »

Certain astrophysical environments such as thermonuclear outbursts on accreting neutron stars (Type-I X-ray bursts) are hot enough to allow for breakout from the Hot CNO hydrogen burning cycles to the rapid proton capture (rp) process. An important breakout reaction sequence is ¹⁵O(α,γ)¹⁹Ne(p,γ)²⁰Na and the ¹⁹Ne(p,γ)²⁰Na reaction rate is expected to be dominated by a single resonance at 457 keV above the proton threshold in 20Na. The resonance strength and, hence, reaction rate depends strongly on whether this ²⁰Na state at an excitation energy of 2647 keV has spin and parity of 1⁺ or 3⁺. Previous ²⁰Mg (J^π = 0⁺)β⁺ decay experiments have relied almost entirely on searches for β-delayed proton emission from this resonance in ²⁰Na to limit the log ft value and, hence, J^π. However there is a non-negligible γ-ray branch expected that must also be limited experimentally to determine the log ft value and constrain . We have measured the β-delayed γ decay of ²⁰Mg to complement previous β-delayed proton decay work and provide the first complete limit based on all energetically allowed decay channels through the 2647 keV state. Our limit confirms that a 1⁺ assignment for this state is highly unlikely.