Univ Napoli Federico II and INFN Napoli 14

Univ. Napoli Federico II and INFN – Napoli 14 th Int. Conf. Nuclear Reaction Mechanisms Istituto Nazionale di Fisica Nucleare New direct measurements of the 19 F(p, α )16 O reaction at very low energies 0 Ivano L ombardo Dip. di Fisica, Università di Napoli Federico II & INFN – Sez. di Napoli ivlombardo@na. infn. it Varenna, 16/06/2015

Univ. Napoli Federico II and INFN – Napoli 19 F(p, a): Other very old paper on this subject a long standing story Fluorine transmutation by proton bombardment Cockroft and Walton studies (~1930) emission of long range a particles

Importance of 19 F(p, a 0) at low energy 19 F(p, a 0) and 19 F(p, ap) at sub-barrier energies quartet states in 20 Ne Univ. Napoli Federico II and INFN – Napoli (Arima, Gillet, Ginocchio PRL 1970) Ambiguities of 20 Ne spectroscopy near the Sp (12. 844 Me. V) (Tilley et al, NPA 1999) Low energy S(E) astrophysical interest (CNO, fluorine nucleosynthesis) ag 12. 84 a 3 p+19 F ap a 2 a 1 7. 12 16. 92 2+ • [211] quartet state in 20 Ne ≈13. 3 + Vres • Ga ≈Gtot (a-structure) • g 2 ap > g 2 a 0 (quartet structure |a+16 O*6. 05>) + • 400 ke. V 0 Gp, a 0, ap (lack of info) 6. 13 36. 05 0+ CNO cycle a 0 GS 0+ 4. 73 a+16 O 0 Ex (Me. V) Two-fold interest 20 Ne

Univ. Napoli Federico II and INFN – Napoli 19 F(p, a 0, p): ambiguities in the literature Breuer 1959 Isoya 1958 (norm. ) Caracciolo 1974 ≈ ≈ 19 F(p, a D. R. Tilley et al, Nucl. Phys. A 636 (1998) 249 Many ambiguities also for the ap channel Devons 1954 Isoya 1958 19 F(p, a p) Caracciolo 1974 NACRE Isoya (norm) vs Breuer data New experiment in Naples a 0 0)

19 F(p, a Univ. Napoli Federico II and INFN – Napoli TTT 3 - Naples 6 Li. F target (95% enriched) Al absorbers 10 ke. V steps Ep = 1. 1 – 0. 6 Me. V accurate Ep calibration 12 detection angles: 20°- 160° R. L. Clarke & E. B. Paul, Can. J. Phys. 35 (1957) 155 G. Breuer, Zeit. Phys. 154 (1959) 339 P. Cuzzocrea et al, Lett. Nuovo Cim. 28 (1980) 515 A. Isoya, Nucl. Phys. 7 (1958) 126 I. Lombardo et al, J. Phys. G 40 (2013) 0): the Naples experiment

19 F(p, a Univ. Napoli Federico II and INFN – Napoli 19 F(p, a 0): experimental S-factor integrated cross section and S-factor Non resonant S(E) 40% larger than NACRE What is happening at 0. 4 – 0. 5 Me. V? Resonances Trojan Horse Method 19 F(p, a 0) La Cognata, APL 739 (2011) L 54 Resonant contributions at low energies?

Univ. Napoli & Catania and INFN – NA, LNS, LNL 19 F(p, a 0) at lower energy @ LNL Ecm = 0. 18 – 0. 6 Me. V very few and old data published in literature a NEW experiment clearly needed !!! AN 2000 Vd. G accelerator - LNL NASPENA @ LNL, Italy I. Lombardo, D. Dell’Aquila, A. Di Leva, I. Indelicato, M. La Cognata, M. La Commara, A. Ordine, V. Rigato, M. Romoli, E. Rosato, G. Spadaccini, C. Spitaleri, A. Tumino and M. Vigilante • • • 12 angles (20 -160 o) angular distributions 30 mg/cm 2 Ca. F 2 target on 20 mg/cm 2 C backing Faraday cup + suppressor Backscattering analysis of target Cross-check with Ruth. cross section 8 mm Al absorber stop protons Good energy resolution clear ejectile identification

19 F(p, a 0) @ LNL: angular distributions Univ. Napoli & Catania and INFN – NA, LNS, LNL Peculiar features of the angular distributions forward peaked at Ecm ≈ 0. 25 - 0. 4 Me. V Some possible interpretations: • interference of states with different Jp • direct effects p t 16 O Reduced Coulomb barrier due to 16 O+t structure in 19 F ? 2+ state at 0. 25 Me. V Ex = 13. 095 Me. V Direct effects at sub-Coulomb energies: [1] G. Raimann et al, Phys. Lett B 249 (1990) [2] H. Herndl et al, Phys. Rev. C 44 (1991)

0) @ LNL: S-factor 0. 38 3 - 0. 25 2+ S – factor at low energies non-resonant extrapolations based on high energy data large ambiguities (≈ 50%) on the reaction rate at stellar energies 0. 113 2+ Univ. Napoli & Catania and INFN – NA, LNS, LNL 19 F(p, a NACR E • Broad state at 13. 095 Me. V (a+16 O scattering) • Interference with the 0. 113 Me. V (Ex =12. 957 Me. V, THM) • RR 1. 5 – 2 times larger than NACRE Complex structure of A≈20 nuclei Ecm Gtot Jp 0. 801 0. 22 0+ 0. 783 0. 25 1 - 0. 733 0. 09 2+ 0. 700 0. 54 2+ 0. 380 0. 40 3 - 0. 251 0. 162 2+ 0. 113 0. 38 2+

Summary Univ. Napoli & Catania and INFN – NA, LNS, LNL • 19 F(p, a) • 19 F(p, a reaction 20 Ne spectroscopy & fluorine nucleosynthesis. 0) at low energy very few data, ambiguities in 20 Ne spectroscopy. • New experiment in Naples (TTT-3 accelerator) 1. 1 – 0. 6 Me. V check Jp assignments and absolute S-factor normalizations. • At lower energies (0. 6 – 0. 2 Me. V) very few data published in the literature, often in relative units new experiment at LNL. • New experiment at LNL (AN 2000 single ended Vd. G accelerator) 0. 6 – 0. 2 Me. V. Non-isotropic angular distributions (direct effects + interference). Effects of various states seen also with the THM. Contribution of the broad 13. 095 Me. V state. • Reaction rate 1. 5 – 2 times larger than the non-resonant estimate by NACRE possible influence on fluorine destruction in metal poor AGB stars via deep-mixing processes. • In memory of Prof. Elio Rosato (1950 - 2014). Thank you for your attention!

Univ. Napoli Federico II and INFN – Napoli Further Slides

19 F(p, a 0): interference of the 2+ states Univ. Napoli Federico II and INFN – Napoli Destructive – constructive – destructive pattern bad fit of data I. Lombardo et al, under review

19 F(p, a 0): non-resonant background Univ. Napoli Federico II and INFN – Napoli S-wave capture (NACRE) FR – DWBA (Yamashita & Kudo, PTP 1994) ≈20% difference in the low-energy S-factor estimate uncertainty I. Lombardo et al, under review

Univ. Napoli Federico II and INFN – Napoli 19 F(p, a 0): the Naples experiment Typical spectrum observed by using 6 Li. F target (95% enriched) 5% 7 Li contaminant 7 Li(p, a) reaction (Q=17. 346 Me. V) I. Lombardo et al, J. Phys. G 40 (2013) TTT 3 - Naples console detection device

19 F(p, a 0): angular distributions and 20 Ne spectroscopy Outgoing channel spin: S = Sa + S 16 Ogs = 0 therefore: Jp 20 Ne* = lf Univ. Napoli Federico II and INFN – Napoli lf analysis of ds/d. W angular distributions cosine and/or Legendre polynomials An(E) and Bn(E) even coefficients resonate at a given energy Scattering matrix calculations lf = n/2 (even coefficients) Odd coefficients anomaly interference between close lying opposite parity states (low Ecm s, p, d waves only) R. L. Clarke & E. B. Paul, Can. J. Phys. 35 (1957) 155 G. Breuer, Zeit. Phys. 154 (1959) 339 P. Cuzzocrea et al, Lett. Nuovo Cim. 28 (1980) 515 19 F(p, a p) A. Isoya, Nucl. Phys. 7 (1958) 126 Ep (ke. V) Absorber technique forward angles a. d.

19 F(p, a 0): angular distributions and 20 Ne spectroscopy Outgoing channel spin: S = Sa + S 16 Ogs = 0 therefore: Jp 20 Ne* = lf Univ. Napoli Federico II and INFN – Napoli lf analysis of ds/d. W angular distributions cosine and/or Legendre polynomials An(E) and Bn(E) even coefficients resonate at a given energy Scattering matrix calculations lf = n/2 (even coefficients) Odd coefficients anomaly interference between close lying opposite parity states (low Ecm s, p, d waves only) R. L. Clarke & E. B. Paul, Can. J. Phys. 35 (1957) 155 G. Breuer, Zeit. Phys. 154 (1959) 339 P. Cuzzocrea et al, Lett. Nuovo Cim. 28 (1980) 515 20 Ne spectroscopy Ep (ke. V) Jp – Tilley NPA (1999) Jp ≈ 650 1 - 1 - 710 [1 -] [1 - ] 733 2+ 2+ 778 2+ 2+ ≈ 825 --- 1 - 842 0+, 2+ 0+ spectroscopy down to Ep=0. 6 Me. V

19 F(p, a 0): Univ. Napoli Federico II and INFN – Napoli Caracciolo et al, LNC 11 (1974) 20 Ne A 2 A 0 20 Ne 840 ke. V region: two close-lying states (opposite parity). dominant state: 842 ke. V 0+ A 1 20 Ne 150° spectroscopy – table Ep (ke. V) spectroscopy down to Ep=600 ke. V spectroscopy Dieumegard et al, NIM 168 (1980) Jp – Tilley Jp NPA (1999) ≈ 650 1 - 1 - 710 [1 -] [1 - ] 733 2+ 2+ 778 2+ 2+ ≈ 825 --- 1 - 842 0+, 2+ 0+

19 F(p, a 0): structure of 20 Ne excited states Univ. Napoli Federico II and INFN – Napoli Integrated cross section partial and reduced width for the a 0 channel Open channels at Ep < 1 Me. V: 19 F(p, p ) elastic scattering 0 19 F(p, p ) inelastic scattering 1 19 F(p, p ) inelastic scattering 2 19 F(p, a ) this work 0 19 F(p, a ) difficult to investigate p Two different sets of gp 2 and ga 02 are reported in the literature for the 842 ke. V state (q 2 ≡ g 2/ g. W 2): Analysis in Lorentz function of experimental data. Reference Jp Gtot (ke. V) Gp 0 (ke. V) Gap (ke. V) q 2 p 0 (%) q 2 ap (%) Isoya 2+ 23 0. 051 9 8. 3 0. 9 0. 16 2. 7 Caracciolo 0+ 23 22. 9 0. 065 10 1. 2 10 -3 10 -2 This work 0+ 23 22. 9 0. 048± 0. 008 0. 065 10 10 -3 10 -2 Low energy states work in progress (few experimental data on (p, p 0) and (p, p’) scattering) a states at lower energies?

Energy calibration of TTT-3 accelerator g spectrum of 19 F(p, ag) around 872 ke. V resonance 3’’ La. Br 3(Ce) Univ. Napoli Federico II and INFN – Napoli courtesy of Prof. Franco Camera, Milan University 6. 12 Me. V 6. 92 Me. V 7. 12 Me. V NMR frequency (k. Hz) Very good energy resolution (0. 1%)

Fluorine nucleosynthesis and the 19 F(p, a 0) reaction 19 F sensitive to physical conditions in stars probe nucleosynthesis scenarios Univ. Napoli Federico II and INFN – Napoli AGB stars possible site of 19 F production [A. Jorissen et al, A&A 261 (1992) 19 F 164] nucleosynthesis still not completely understood [S. Cristallo et al, A&A 570 (2014) A 46] Abia [C. Abia et al, APJL 737 (2011) 8] and Lucatello [S. Lucatello et al, Astr. J. 729 (2011) 40] fluorine observation on metal poor AGB stars 19 F upper limits well lower than theoretical models why? A possible explanation deep mixing phenomena can alter the stellar outerlayer isotopic composition 19 F(p, a) an important destruction reaction T ≈ 0. 04 GK Gamow window 0. 03 -0. 1 Me. V S. Lucatello et al, Astr. J. 729 (2011) 40 a 0 channel dominant on ap and ag [K. Spyrou et al, EPJA 7 (1999)] State of art of nuclear reaction data?