Electron-Capture Rates for
Exotic Nuclei
at Stellar Environments
Toshio Suzuki
Nihon University
ARIS2014
June 2, 2014

・ GT strengths in Ni and Fe isotopes by new shellmodel Hamiltonians, GXPF1J・ Electron capture rates for Ni, Fe, (Co, Mn) isotopes
at stellar environments
・ Type-Ia supernova explosions and nucleosynthesis
56

Ni(e , )56Co

・ rp-process and XRB (X-ray burst)
55

Ni(e , ) Co
55

・ Type-II core-collapse supernova explosions
e-capture rates on Fe isotopes

○ New shell-model Hamiltonians in fp-shell:
GXPF1: Honma et al., PR C65 (2002); C69 (2004)
KB3: Caurier et al., Rev. Mod. Phys. 77, 427 (2005)○ KB3GA = 47-52
KB + monopole corrections○ GXPF1 A = 47-66
・ Spin properties of fp-shell nuclei are well describedM1 strength
B(GT-) for 58Ni gAeff/gAfree=0.74(GXPF1J)
Fujita et al.
gSeff/gS=0.75±0.2
8-13MeV

●Electron-capture rate in stellar environmente   Z A    Z 1 AT  0 :   M( Z A)  M( Z 1 A)
  M( Z 1 A)  M( Z A)

Ye  107 1010 g / cm3
T  T9  109 K
ln 22 B j ( GT )e  p( Q j   ) F ( Z , )Se (  )d6146( s ) jQ j  ( M p c 2  M d c 2  E j ) / me c 2
T  T9 109 K ,Ye Se ( Ee ) 1
exp[( Ee   e ) / kT ]  1

me c 3 
1()  ( Se  S p ) p 2dp2 NA0 p  e

Chemical potential of e- (μ)
increases at high density

f7/2 -> f5/2e-capture rates instellar environments

f7/2 -> f7/2
PRL 107, 202501 (2011) f7/2 -> f5/2
Sasano et al.

Ye  107 1010 g / cm3
T  T9  109 K

58Ni → 58Co60Ni → 60Co

Exp: Hagemann et al., PL B579 (2004)

Exp: Anantaraman et al., PR C78 (2008)

Type-Ia supernova explosion
Accretion of matter to white-dwarf from binary star→ supernova explosion when white-dwarf mass > Chandrasekhar limit→ 56Ni (N=Z)→ 56Ni (e-, ν) 56Co Ye =0.5 → Ye < 0.5 (neutron-rich)→ production of neutron-rich isotopes; more 58Ni
Decrease of e-capture rate on 56Ni → less production of 58Ni.

e-capture rates:
GXPF1J < KB3G←→ Ye (GXPF1J) > Ye (KB3G)

FamianoProblem of over-production of 58Ni

NSE(Nuclear StatisticalEquilibrium) calculation

Ye

54Cr58Ni

54Fe

GXPF1 -> 58Ni/56Ni decreases

56FeFamiano

Sasano et al.

rp-process and X-ray burst(p, γ) & β+-decay/e-capture50

Fe (, e  )50 Mn

5550Fe (e ,  )50 Mn

Ni (e ,  )55 CoZParikh et al., PPNP 69, 225 (2013)NX-ray burst
e-capture and beta-decay
rates with KBF:
56Ni

Langanke and Martinez-Pinedo,
Atomic Data and Nuclear Data
Tables 79, 1 (2001)

60Zn, 64Ge, 68Se

Sn-Sb-Te cycle

FamianoType-II Core-Collapse SNeRates for 54Fe, 55Fe, 56Fe, 57Fe
GXPF1J vs. KBF

KBF

Langanke and Martinez-Pinedo,
RMP 75 (2003)

Rates for 54Fe, 56Fe
GXPF1J vs. KBF

e-capture rates
GXP > KBF
for 54,55,56Fe
Ye for GXP
GXP < KBF
for 57Fe
Ye for GXPYe=107 ～1010
Langanke and Martinez-Pinedo,
Atomic and Nucl. Data Tables (2001)
FFN: Astrophys. J. Suppl. (1982)

Summary• A new shell model Hamiltonian GXPF1J well describes
the spin responses in fp-shell niclei→ new GT strengths in Ni and Fe isotopes
・ GT strengths and electron capture rates in 56Ni, 55Co,
58Ni , 60Ni are well described by GXPF1J.
Suzuki, Honma, Mao, Otsuka, Kajino, PR C83, 044619 (2011)

・ Effects on Type Ia SNe nucleosynthesis, rp-process andXRB, Type-II core-collapse SNe are discussed
Collaborators
M. Honmaa, T. Otsukab, T. Kajinoc,d, M. FamianoaUniversity of Aizu
bDepartment of Physics and CNS, University of Tokyo
cDepartment of Astronomy, University of TokyodNational Astronomical Observatory of Japan