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David Mountford University of Edinburgh

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2 David Mountford University of Edinburgh
Resonances in 19Ne with relevance to the astrophysically important 18F(p,α)15O reaction David Mountford University of Edinburgh

3 Contents Novae The importance of 18F Previous work The Experiment
Preliminary Results Conclusions

4 Novae White dwarf accretes hydrogen-rich matter onto its surface
The bottom layer of accreted matter is compressed and heated, triggering hydrogen burning and eventually thermonuclear runaway Degeneracy lifted – outer layers blown off

5 18F in Novae High temperatures in the nova explosion trigger hot CNO cycle: 12C 13N 14O 14N 15O 17F 18Ne 19Ne 18F 18F 15O unstable stable (,) (p,) (b+) (p,) (,p) 18F produced by β+ decay of 18Ne 18F destruction by (p,α):

6 18F in Novae (cont.) 18F relatively abundant in novae Decays via β+:
t1/2 ~ 110mins Some of most abundant γ-rays at <511keV are likely to come from the positron annihilation associated with this decay Satellites searching for such gamma rays…

7

8 19Ne Reaction proceeds through excited states of the compound nucleus 19Ne States above the 18F+p threshold can be explored Ebeam 1.9MeV 2.88MeV 6.41MeV 18F+p 15O+α 19Ne

9 19Ne (cont.) The generator coordinate method and the mirror nucleus have inferred 2 new ½+ states in 19Ne[1], one above and one below 18F+p threshold Sub threshold state broad enough to impact upon 18F(p,α)15O Lower limit placed on reaction rate: [1] Dufour and Descouvemont, Nucl. Phys. A 785 (2007) 381–394

10 19Ne (cont.) The generator coordinate method and the mirror nucleus have inferred 2 new ½+ states in 19Ne[1], one above and one below 18F+p threshold Sub threshold state broad enough to impact upon 18F(p,α)15O Lower limit placed on reaction rate: [5] C.E.Beer et al., Phys. Rev. C83, (R) (2011)

11 Previous Work: Descouvemont States
Dalouzy et al. (2009)[2] see the new peak at Ex = 7.863(39)MeV 1.452MeV above 18F + p threshold [2] Dalouzy et al., Phys. Rev. Lett. 102, (2009)

12 Previous Work: Descouvemont States
Murphy et al. (2009)[3] see states at and MeV None as in Dalouzy Must repeat to higher energies [3] Murphy et al., Phys. Rev. C 79, (2009)

13 The Experiment Energy on CH2 ~2MeV/u (~1.9MeV CM)
3.9MeV/u 18F beam 1mm thick, 50x50 mm DSSSD ~54.7µm CH2 ~6µm Au Degrader Energy on CH2 ~2MeV/u (~1.9MeV CM) Higher energy than any previous works Beam stops in target Carried out at GANIL, Caen from 11th to 16th April 2010:

14 Measurements Contaminant Time of Flight Protons Alpha particles
Carbon ions Elab

15 Preliminary Results

16 Preliminary Results Ecm (MeV) Jπ Γp(keV) Γα(keV) Int A 0.665 3/2+ 15 24 + B 0.759(20) 1.6(5) 2.4(6) C 1.096(11) 5/2+ 3(1) 54(12) D 1.160(34) 2.3(6) 1.9(6) E 1.219(22) 3/2- 21(3) 0.1(1) F 1.335(6) 65(8) 26(4) - G 1.455(38) 1/2+ 55(12) 347(92) H 1.571(13) 1.7(4) 12(3) Results of R Matrix analysis carried out using DREAM code from P. Descouvemont Comparison references: Nesaraja et al. PRC 75, (2007) Murphy et al. PRC 79, (2009) Dalouzy et al. PRL 102, (2009)

17 Preliminary Results (A)
Ecm (MeV) Jπ Γp(keV) Γα(keV) Int A 0.665 3/2+ 15 24 + B 0.759(20) 1.6(5) 2.4(6) C 1.096(11) 5/2+ 3(1) 54(12) D 1.160(34) 2.3(6) 1.9(6) E 1.219(22) 3/2- 21(3) 0.1(1) F 1.335(6) 65(8) 26(4) - G 1.455(38) 1/2+ 55(12) 347(92) H 1.571(13) 1.7(4) 12(3) A Well known ‘665keV’ state Cross sections scaled to this state

18 Preliminary Results (B)
Ecm (MeV) Jπ Γp(keV) Γα(keV) Int A 0.665 3/2+ 15 24 + B 0.759(20) 1.6(5) 2.4(6) C 1.096(11) 5/2+ 3(1) 54(12) D 1.160(34) 2.3(6) 1.9(6) E 1.219(22) 3/2- 21(3) 0.1(1) F 1.335(6) 65(8) 26(4) - G 1.455(38) 1/2+ 55(12) 347(92) H 1.571(13) 1.7(4) 12(3) A B Reported by Nesaraja/Dalouzy Significantly weaker than Dalouzy Consistent in strength with Nesaraja

19 Preliminary Results (C & D)
Ecm (MeV) Jπ Γp(keV) Γα(keV) Int A 0.665 3/2+ 15 24 + B 0.759(20) 1.6(5) 2.4(6) C 1.096(11) 5/2+ 3(1) 54(12) D 1.160(34) 2.3(6) 1.9(6) E 1.219(22) 3/2- 21(3) 0.1(1) F 1.335(6) 65(8) 26(4) - G 1.455(38) 1/2+ 55(12) 347(92) H 1.571(13) 1.7(4) 12(3) A B C D C reported by Murphy – narrower but current result relatively consistent C and D reported by Dalouzy/Nesaraja at different strengths C in good agreement in energy

20 Preliminary Results (E)
Ecm (MeV) Jπ Γp(keV) Γα(keV) Int A 0.665 3/2+ 15 24 + B 0.759(20) 1.6(5) 2.4(6) C 1.096(11) 5/2+ 3(1) 54(12) D 1.160(34) 2.3(6) 1.9(6) E 1.219(22) 3/2- 21(3) 0.1(1) F 1.335(6) 65(8) 26(4) - G 1.455(38) 1/2+ 55(12) 347(92) H 1.571(13) 1.7(4) 12(3) A B C D E Previously reported by Nesaraja and Murphy Agreement in spin with Murphy No agreement in strength Required to fit bottom of state F

21 Preliminary Results (F)
Ecm (MeV) Jπ Γp(keV) Γα(keV) Int A 0.665 3/2+ 15 24 + B 0.759(20) 1.6(5) 2.4(6) C 1.096(11) 5/2+ 3(1) 54(12) D 1.160(34) 2.3(6) 1.9(6) E 1.219(22) 3/2- 21(3) 0.1(1) F 1.335(6) 65(8) 26(4) - G 1.455(38) 1/2+ 55(12) 347(92) H 1.571(13) 1.7(4) 12(3) A B C D E F Observed by Murphy with less strength New strength due to strong correlation with state G

22 Preliminary Results (G)
Ecm (MeV) Jπ Γp(keV) Γα(keV) Int A 0.665 3/2+ 15 24 + B 0.759(20) 1.6(5) 2.4(6) C 1.096(11) 5/2+ 3(1) 54(12) D 1.160(34) 2.3(6) 1.9(6) E 1.219(22) 3/2- 21(3) 0.1(1) F 1.335(6) 65(8) 26(4) - G 1.455(38) 1/2+ 55(12) 347(92) H 1.571(13) 1.7(4) 12(3) A B C D E F G Descouvemont state? Stay tuned…

23 Preliminary Results (H)
Ecm (MeV) Jπ Γp(keV) Γα(keV) Int A 0.665 3/2+ 15 24 + B 0.759(20) 1.6(5) 2.4(6) C 1.096(11) 5/2+ 3(1) 54(12) D 1.160(34) 2.3(6) 1.9(6) E 1.219(22) 3/2- 21(3) 0.1(1) F 1.335(6) 65(8) 26(4) - G 1.455(38) 1/2+ 55(12) 347(92) H 1.571(13) 1.7(4) 12(3) A B C D E F G H Observed by Dalouzy (alternative π) and Murphy (alternative J) Dalouzy J unambiguous but π inferred Current data strongly favours Jπ=5/2+ at consistent strengths

24 Dufour/Descouvemont State??
Candidate state observed at ECM=1.455MeV (G) More than a factor of 2 narrower than predicted in proton channel More than a factor of 2 broader than predicted in alpha channel But consistent in total width (402(93)keV) with Dalouzy (292(107)keV Broad state is required to fit to data

25 Conclusions New data obtained in study of astrophysically important 18F(p,α)15O reaction New work finds candidate for a newly predicted, ½+ state consistent with previous measurement Existence of partner sub-threshold state could significantly enhance 18F in Novae

26 Collaborators References University of Edinburgh: University of York:
A. S. Murphy T. Davinson P. J. Woods University of York: A. M. Laird J. R. Brown Orsay: N. de Sereville Tractebel: C. Angulo LPC Caen N. L. Achouri GANIL F. de Oliveira P. Ujic O. Kamalou ORNL: S. T. Pittman ULB: Pierre Descouvemont References [1] Dufour and Descouvemont, Nucl. Phys. A 785 (2007) 381–394 [2] Dalouzy et al., Phys. Rev. Lett. 102, (2009) [3] Murphy et al., Phys. Rev. C 79, (2009) [4] Nesaraja et al. Phys. Rev. C 75, (2007) [5] C.E.Beer et al., Phys. Rev. C83, (R) (2011)

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