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
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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
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(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 .
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