Beta-decay of neutron-rich Ni and Cu isotopes in a shell model approach

Alexander Lisetskiy

Hirschegg 2006

Exotic regions

Shell Model Effective Interaction

Fitting Landscape

Ni + Cu isotopes + N=49,48 isotones

A. F. Lisetskiy, B. A. Brown, M. Horoi, H. Grawe, PRC 70, 044314, (2004)

Nuclear structure phenomena near 78Ni

• No seniority isomers in 72Ni and 74Ni

• No high-spin isomers in 73Cu,75Cu and 77Cu

• No 8+ isomers in 72Zn,74Zn,76Zn • 5/2- ground state in 75Cu,77Cu and 79Cu

• Pseudo-magicity of 68Ni

Theoretical tools for beta-decay studies

Global picture:

Finite Range Droplet Model +QRPA (P. Moeller, K. L. Kratz)

Self-consistent HF-BCS + continium QRPA(I. Borzov, S. Fayans)

Local picture: Shell Model with effective interactions Unified picture for many different properties of particular nucleus

Model Space

Importance! Sn : for r-process path Pn : abundance pattern T1/2 : timescale, abundance pattern

Sn – neutron separation energy Pn – branching of beta delayed neutron emission

beta-decay scheme

(Z,A)

(Z+1,A)

(Z+1,A-1)Sn

n

Q

Ni beta-decay: Energetics

Q(A,Z) = M(A,Z) - M(A,Z+1)

Ni beta-decay: Energetics

Sn(A,Z) = B(A,Z) - B(A-1,Z)

Ni beta-decay: Half-lives

Quenching for Gamow -Teller operator: q=0.37!Common q value is 0.70-0.75

P. T. Hosmer et al., PRL 94, 112501 (2005)

Ni beta-decay: Half-lives

Quenching factor is Q-value dependent

Ni beta-decay: beta-delayed n-emission

Pn = GT branching for states with Q > Eexc > Sn

H. Schatz, in prep. (MSU data)

Cu beta-decay: Energetics

Q(A,Z) = M(A,Z) - M(A,Z+1)

Cu beta-decay: Energetics

Sn(A,Z) = B(A,Z) - B(A-1,Z)

Cu beta-decay: Half-lives

Quenching for Gamow -Teller operator: q=0.37!Common q value is 0.70-0.75

P. T. Hosmer et al., PRL 94, 112501 (2005)

Cu beta-decay: Half-lives

Quenching factor is Q-value dependent

Cu beta-decay: beta-delayed n-emission

Pn = GT branching for states with Q > Eexc > Sn

H. Schatz, in prep. (MSU data)

75Ni: B(GT) distribution

78Ni: beta-decay

f7/2 included f7/2 included

x10

Summary & Outlook

• Improved shell model effective interaction for the p3/2p1/2f5/2g9/2 space in action

• Self-consistent good description of beta-decay data for Ni and Cu isotopes

• Strong quenching of GT strength: origin ? Large-scale shell model calculations

• Tests for Zn and Ga beta-decay

• rp-process nuclei: 64Ge, 68Se

• Role of first forbidden transitions

Collaborators

Alex Brown, NSCL, MSU

Mihai Horoi, CMU

Hendrik Schatz, JINA, NSCL, MSU

GSI:

K. Langanke

G. Matrinez-Pinedo