Is gamma-Ray Emission from Novae Affected by Interference Effects in the F-18(p, alpha)O-15 Reaction?

TY - JOUR

T1 - Is gamma-Ray Emission from Novae Affected by Interference Effects in the F-18(p, alpha)O-15 Reaction?

AU - Laird, A. M.

AU - Parikh, A.

AU - Murphy, A. St. J.

AU - Wimmer, K.

AU - Chen, A. A.

AU - Deibel, C. M.

AU - Faestermann, T.

AU - Fox, S. P.

AU - Fulton, B. R.

AU - Hertenberger, R.

AU - Irvine, D.

AU - Jose, J.

AU - Longland, R.

AU - Mountford, D. J.

AU - Sambrook, B.

AU - Seiler, D.

AU - Wirth, H. -F.

N1 - 5 pages, 4 figures. Accepted for publication in Phys. Rev. Lett

PY - 2013/1/15

Y1 - 2013/1/15

N2 - The 18F(p, alpha)O-15 reaction rate is crucial for constraining model predictions of the gamma-ray observable radioisotope F-18 produced in novae. The determination of this rate is challenging due to particular features of the level scheme of the compound nucleus, Ne-19, which result in interference effects potentially playing a significant role. The dominant uncertainty in this rate arises from interference between J(pi) = 3/2(+) states near the proton threshold (S-p = 6.411 MeV) and a broad J(pi) = 3/2(+) state at 665 keVabove threshold. This unknown interference term results in up to a factor of 40 uncertainty in the astrophysical S-factor at nova temperatures. Here we report a new measurement of states in this energy region using the F-19(He-3, t)Ne-19 reaction. In stark contrast to previous assumptions we find at least 3 resonances between the proton threshold and E-cm = 50 keV, all with different angular distributions. None of these are consistent with J(pi) = 3/2(+) angular distributions. We find that the main uncertainty now arises from the unknown proton width of the 48 keV resonance, not from possible interference effects. Hydrodynamic nova model calculations performed indicate that this unknown width affects F-18 production by at least a factor of two in the model considered. DOI: 10.1103/PhysRevLett.110.032502

AB - The 18F(p, alpha)O-15 reaction rate is crucial for constraining model predictions of the gamma-ray observable radioisotope F-18 produced in novae. The determination of this rate is challenging due to particular features of the level scheme of the compound nucleus, Ne-19, which result in interference effects potentially playing a significant role. The dominant uncertainty in this rate arises from interference between J(pi) = 3/2(+) states near the proton threshold (S-p = 6.411 MeV) and a broad J(pi) = 3/2(+) state at 665 keVabove threshold. This unknown interference term results in up to a factor of 40 uncertainty in the astrophysical S-factor at nova temperatures. Here we report a new measurement of states in this energy region using the F-19(He-3, t)Ne-19 reaction. In stark contrast to previous assumptions we find at least 3 resonances between the proton threshold and E-cm = 50 keV, all with different angular distributions. None of these are consistent with J(pi) = 3/2(+) angular distributions. We find that the main uncertainty now arises from the unknown proton width of the 48 keV resonance, not from possible interference effects. Hydrodynamic nova model calculations performed indicate that this unknown width affects F-18 production by at least a factor of two in the model considered. DOI: 10.1103/PhysRevLett.110.032502

KW - STATES

KW - SHELL NUCLEI

KW - NUCLEOSYNTHESIS

KW - NE-19

UR - http://www.scopus.com/inward/record.url?scp=84872291621&partnerID=8YFLogxK

U2 - 10.1103/PhysRevLett.110.032502

DO - 10.1103/PhysRevLett.110.032502

M3 - Article

SN - 0031-9007

VL - 110

SP - 1

EP - 5

JO - Physical Review Letters

JF - Physical Review Letters

IS - 3

M1 - ARTN 032502

ER -