Astrophysical S-factors for the p+16O and n+16O captures from the analysis of 16O(d,n)17F and 16O(d,p)17O transfer reactions

AIP Con e ence P oceedings 884, 158 (2007); h ps://doi.o g/10.1063/1.2710573 884, 158 © 2007 Ame ican Ins i u e o Physics. As ophysical S- ac o s o he p+16O and n+16O cap u es om he analysis o 16O(d,n)17F and 16O(d,p)17O ans e eac ions Ci e as: AIP Con e ence P oceedings 884, 158 (2007); h ps:// doi.o g/10.1063/1.2710573 Published Online: 22 Feb ua y 2007 M. Assunção, R. Lich en häle , V. Guima ães, A. Lépine-Szily, and A. M. Mo o ARTICLES YOU MAY BE INTERESTED IN Ligh adioac i e nuclei cap u e eac ions wi h phenomenological po en ial models AIP Con e ence P oceedings 1245, 30 (2010); h ps:// doi.o g/10.1063/1.3448012 As ophysical S- ac o s o he p+16 Oand n+16 Ocap u es om he analysis o 16O(d,n)17F and 16O(d,p)17O ans e eac ions M. Assunção∗, R. Lich en häle ∗, V. Guima ães∗, A. Lépine-Szily∗and A. M. Mo o† ∗Depa amen o de Física Nuclea , Ins i u o de Física da Uni e sidade de São Paulo, CP 66318, 05315-970 São Paulo SP, B azil. †Depa amen o de Física, Ins i u o Supe io Técnico, Taguspa k, 2780-990 Po o Sal o, Po ugal and Depa amen o de FAMN, Uni e sidad de Se illa, Apdo. 1065, E-41080 Se illa, Spain. Abs ac . Coupled eac ion channels calcula ions we e pe o med o he 16O(d,n)17Fand 16O(d,p)17O ans e eac ions o he g ound and i s exci ed s a es a se e al ene gies om Elab=2.29 MeV up o 3.27 MeV. A s ong pola iza ion e ec be ween he en ance channel and he ans e , 16O(d,n)17F(1/2+,0.495) and 16O(d,n)17O(1/2+,0.87), channels was obse ed. This pola iza ion e ec had o be aken in o accoun o all o de s o ob aining ealis ic spec oscopic ac- o s om hese eac ions. The 16O(p, γ )17Fand 16O(n, γ )17Odi ec cap u es we e calcula ed using he Asymp o ic No maliza ion Coe icien s (ANC) alues om hese ans e eac ions analysis. The as ophysical S- ac o s we e compa ed o measu emen s. The Maxwellian-a e aged neu on cap u e c oss sec ion a kT=30 keV was 22(3) μ ba n. Keywo ds: di ec eac ion, coupled-channel, dis o ed-wa e model, cap u e c oss sec ion, as o- physical S- ac o PACS: 24.10.Eq, 24.50.+g, 25.70.-z, 25.45.-z INTRODUCTION The in e es in he expe imen al and heo e ical s udy o ew nucleon ans e eac ions has been enewed in he las yea s mainly due o he possibili y o ob aining as ophysi- cal ele an in o ma ion om hese eac ions [1, 2, 3, 4, 5]. The di ec measu emen s o cap u e eac ions a ene gies o as ophysical in e es a e, in some cases, nea ly impossi- ble due o low eac ion yield, especialy i he cap u e in ol es exo ic nuclei. Al e na i e indi ec me hods such as he asymp o ic no maliza ion coe icien (ANC) me hod, based on he analysis o b eakup [6] o ans e eac ion [1] ha e been used as a ool o ob- aining as ophysical S- ac o s. The ad an age o he indi ec app oach comes om he ac ha he ans e and b eakup eac ions can be measu ed a highe ene gies, whe e he c oss sec ions a e much la ge . Howe e , in o de o ob ain use ul in o ma ion om ans e eac ions one needs o unde s and, as clea as possible, he eac ion mechanism he ein in ol ed. In his pape , we in es iga e he impo ance o conside ing he CRC (coupled eac ion channel) calcula ion in he analysis o he 16O(d,n)17Fand 16O(d,p)17O ans e eac- ions, a inciden deu e on ene gies om Ed=2.279 MeV o Ed=3.155 MeV, o which expe imen al da a exis [7]. By pe o ming CRC calcula ions and compa ing o DWBA 158 CREDIT LINE (BELOW) TO BE INSERTED ON THE FIRST PAGE OF EACH PAPER CP884, VI La in Ame ican Symposium on Nuclea Physics and Applica ions, edi ed by O. Ci i a ese, C. Do so, G. Ga cía Be múdez, A. J. K eine , A. J. Pacheco, and N. N. Scoccola © 2007 Ame ican Ins i u e o Physics 978-0-7354-0388-8/07/$23.00 (dis o ed wa e Bo n app oxima ion) and CCBA (coupled channel Bo n app oxima ion) esul s, we show ha i ealis ic spec oscopic in o ma ion is o be ob ained om hese eac ions one has o go beyond he Bo n app oxima ion.We use he spec oscopic ac o s ob ained om a ull CRC calcula ion o e alua e he p+16 Oand n+16 Ocap u e c oss sec ions. In pa icula , he la ge 16O(n, γ )17Oc oss sec ion ob ained has implica ions o nucleosyn esis heo ies, especially in me al-de icien massi es a s as an impo an neu- on poison [8]. DWBA AND CCBA ANALYSIS Fi s ly, he ans e eac ions we e analyzed in e ms o he DWBA app oach. The dis- o ing po en ial o he en ance channel was conside ed as a a ia ion o he Sa chle pa ame iza ion [9] sligh ly modi ied o imp o e he i o he d+16 Oangula dis ibu- ion. The op ical po en ials in he exi channels we e ob ained om pa ame iza ion o Rosen [10]. These po en ials a e lis ed in Table 1 and he spin-o bi con ibu ions a e VS0=6.0 MeV, S0=1.4 m and aS0=0.7 m o he d+16O sys em. Bo h n+17F and p+17O sys ems ha e been conside ed he alues o VS0=5.5 MeV, S0=1.25 m and aS0=0.65 m. TABLE 1. Op ical po en ial pa ame e s used in DWBA and CCBA analysis. Sys em V0 0a0Wd iai (MeV) ( m) ( m) (MeV) ( m) ( m) d+16O 110.0 1.012 0.876 9.3 1.837 0.356 n+17F -49.3+0.33Ec.m.1.25 0.65 5.75 1.25 0.70 p+17O -53.8+0.33Ec.m.1.25 0.65 7.5 1.25 0.70 Se (CRC) 104 1.25 0.65 24.9 1.25 0.233 The DWBA calcula ion is in good ag eemen wi h he g ound s a e o (d,n0)and (d,p0) eac ions a o wa d angles, while a clea o e es ima ion o he i s exci ed s a e o (d,n1)and (d,p1)is obse ed in lowe pannels o Figu e 1.(a) and 1.(b). In hese cases, he spec oscopic ac o o abou 0.6 would be equi ed o i he da a wha is no consis en wi h he single-pa icle cha ac e expec ed o he 17Fand 17Onuclei. In all calcula ions, a compound nucleus con ibu ionsob ained by Die zch e al. [7] we e sub ac ed om expe imen al da a. One o he main sou ces o ambigui y in he DWBA calcula ions p esen ed abo e is he op ical po en ial o he exi channels (n+17 Fo p+17 O) o which no expe imen al da a exis s. In he o me case, he weakly bound na u e o he 17F(1/2+,0.495) s a ep oduces a long ailin hebound s a ewa e unc ion, making he sys em mo e di use han he g ound s a e. The e o e, he di e en cha ac e o hese wo s a es migh cas doub on he alidi y o he global pa ame iza ion [10] used o desc ibe hen+17F∗elas icsca e ing.In addi ion, couplings be ween heg ound and exci ed s a es o 17Fa e neglec ed in he DWBA calcula ions. These e ec s can be p ope ly aken in o accoun by using he CCBA o malism. By pe o ming he CCBA calcula ions, we no ed ha he esul s a e e y simila o he DWBA esul s, indica ing ha he inal s a e in e ac ion a ising om a ge exci a ion plays a negligible ole in his eac ion [11]. 159 CRC CALCULATIONS P e ious sec ion has shown ha bo h DWBA and CCBA calcula ions do no qui e ep o- duce he ans e c oss sec ion o he 16O(d,n)17F∗and 16O(d,p)17O∗ eac ions, unless un easonably small spec oscopic ac o s a e used o he 17F∗|16Oand 17O∗|16O o e laping wa e unc ions. The accu acy o bo h, he DWBA and CCBA app oaches, ely on he alidi y o he Bo n app oxima ion. In he CRC app oach, he op ical po en ials o he en ance and exi channels couldbe unde s ood as ba e po en ials. Once he ans e couplings a e se in bo h di ec ions, he ba e po en ials is de ined as o ep oduce he elas ic sca e ing o he espec i e channel. We used he sea ch e sion SFRESCO [12] code o de e mine he ba e po en ial in he en ance channel by a ying V0,Wd,aiand he spec osopic ampli ude in o de o i simul aneously he elas ic (d+16 O)da a and ans e channels a 2.85 MeV. The ob ained alues o V0,Wdand aia e lis ed in he Table 1. The op ical po en ials in he exi channels we e kep ixed o he Rosen pa ame iza ion. The bes i o Se (CRC) is lis ed in Table 1. Resul s using his se o pa ame e s, a e p esen ed in Figu e 1.(a), 1.(b) and 1.(c). Fo compa ison pu poses,The DWBA p edic ion,assuminguni spec oscopic ac o , is also included in he igu e. The CRC (d,d) (solid lines in Figu e 1.(c)) is in e y good ag eemen wi h he da a. Fu he mo e, he CRC calcula ion p oduces a educ ion o he c oss sec ion a o wa d angles o he (d,n1)and (d,p1) eac ions, imp o ing signi ican ly he ag eemen wi h he expe imen al da a using spec oscopic ac o s close o one. FIGURE 1. (a) CRC calcula ions (solid line) o he 16O(d,n)17Fand (b) 16O(d,p)17O eac ions o he g ound (uppe pannels) and i s exci ed (lowe pannels) s a es a 2.85 MeV, using he Se (CRC) o pa ame e s (see Table 1). (c) Expe imen al and calcula ed elas ic angula dis ibu ions o d+16 O a Ed=2.85 MeV. The expe imen al da a we e ob ained by Diezsch e al. and CN con ibu ions [7] a e included. We ha e ex ended he CRC analysis o o he ene gies, i.e., om Ed= 2.29 o Ed= 3.186 MeV o he (d,n) eac ion and om Ed= 2.279 o Ed= 3.155 MeV o he (d,p) eac ion. The a e age spec oscopic ac o s ob ained om his analysis a e summa ized in Table 2. The s anda de ia ion speci ied as he e o o he spec oscopic ac o s we e 160 ob ained om he a e age o ou analyzed ene gies. Excep o he (d,p1)channel, all spec oscopic ac o s a e close o one. The small alue o he 17O∗|16Ospec oscopic ac o should be conside ed as an open p oblem in ou analysis. TABLE 2. A e age spec oscopic ac o s and ANC alues om CRC calcula ions. (d,p0)(d,p1)(d,n0)(d,n1) Spec oscopic Fac o 1.19(5) 0.69(17) 0.93(11) 0.96(12) ANC Values ( m−1) 0.88(3) 6(1) 0.85(7) 6017(493) PROTON AND NEUTRON CAPTURE CROSS SECTIONS In o de o ge eliable ANC alues om he spec oscopic ac o s i is necessa y o assu e ha he ans e eac ions a e pe iphe al. Fo his pu pose we pe o med es s in ou p e ious DWBA calcula ions by a ying he lowe cu in he DWBA in eg als and obse ing he sensi i i y o he calcula ions. The esul s o hese es s indica ed ha one calcula ions we e p ac ically insensi i e o cu s un il cu ∼5 m and become e y sen i eabo e cu =6 m showing ha he ans e eac ions a e qui e pe iphe al [13]. The ob ained ANC alues o p+16 Oand n+16 Oa e shown in Table 2. FIGURE 2. (a)As ophysicalS- ac o om 16O(d,n)17F ans e eac ion and (b)neu oncap u e c oss sec ion om 16O(d,p)17O ans e eac ion pe o medby CRC analysis. The solid lines a e ou esul s and he dashed lines a e e o bands. The do ed line in (b) was ob ained using he spec oscopic ac o equal o one. The expe imen al da a we e ob ained by Mo lock e al. [15] and by Igashi a e al.[8] ( esonance e ec a e included), espec i ely. The as ophysical S- ac o s o he 16O(p, γ )17Fand 16O(n, γ )17Ocap u e c oss sec- ions we e de e mined using he p og am Radcap [14]. The esul s a e shown in Figu e 2 (a) and (b) compa ed o expe imen al da a o Mo lock e al. [15] and Igashi a e al. [8], espec i ely. The ze o ene gy S- ac o o he i s exci ed s a e 16O(p, γ )17F∗was ob ained as 9.6±0.8 keVba n and i is in ag eemen wi h he alue o Gaglia di e al [4]. Fo he g ound s a e in bo h S- ac o calcula ions unde es ima e he expe imen al da a, 161 howe e , Mo lock e al. [15] sugges ha he g ound expe imen al da a could ha e been con amina ed by he backg ound [15]. The neu on cap u es o he g ound and i s exci ed s a es o he 17Onucleus a e shown in Figu e 2.(b). The Maxwellian-a e aged di ec c oss sec ion a kT=30 keV was calcula ed as 22±3 μ ba n om ou ans e eac ion analysis. Igashi a e al. [8] epo ed a 34±4 μ ba n om expe imen al da a wi h he esonance e ec sub ac ed. This la ge c oss sec ion esul could ha e implica ions o nucleosyn hesis heo ies and inhomogeneous models [8]. CONCLUSIONS We in es iga ed in de ail he mechanism o he 16O(d,n)17Fand 16O(d,p)17O ans e eac ions a e y low ene gies. We ha e shown ha s anda d DWBA and CCBA calcula- ions do no ep oduce he (d,n1)and (d,p1) eac ions unless e y small spec oscopic ac o s a e used, while he CRC calcula ions g ea ly imp o e he ag eemen wi h he (d,n1)and (d,p1)channels. The spec oscopic ac o ob ained om he CRC analysis is close o uni in ag eemen wi h heo e ical p edic ions. The ob ained as ophysical S- ac o s o he 16O(p, γ )17F∗and 16O(n, γ )17Ogs cap u e eac ions a e in good ag ee- men wi h he expe imen al measu emen s. The 16O(p, γ )17Fgs and 16O(n, γ )17O∗c oss sec ions ob ained in his wo k unde es ima e he expe imen al da a. The Maxwellian- a e aged c oss sec ion a kT=30keV o he o al (gs+1s exc)16O(n, γ )17Ocap u e, has been de e mined o be 22(3) μ b. The p esen esul s demons a e he possibili yo de e - mining as ophysical S- ac o s om ans e eac ion measu emen s. ACKNOWLEDGMENTS The au ho s woud like o hank FAPESP and CNPq o inancial suppo . REFERENCES 1. H.M. Xu e al. Phys. Re . Le .,73,(1994), 2027. 2. A.M. Mukhamedzhano e al. Phys. Re . C56,(1997) 1302. 3. J. C. Fe nandes, R. C espo, and F. M. Nunes Phys. Re . C64, (2001) 062801(R). 4. C. A. Gaglia di e al. Phys. Re . C59, 1149 (1999). 5. L.T ache e al. Phys. Re . Le . 87, 271102 (2001). 6. N. Imai e al. Nucl. Phys. A688, 281c-284c (2001). 7. O. Die zsch e al. Nucl. Phys. A114, 330 (1968). 8. M. Igashi a e al. As ophys. J. Le .,441, L89-L92 (1995). 9. G.R. Sa chle Nucl.Phys. 85, 273 (1966). 10. L. Rosen P oceedings o he 2nd In e na ional Symposium on Pola iza ion Phenomena o Nucleons, Bi khause Ve lag, Basel, 1966, p. 253. 11. M. Assunção e al. Phys. 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