XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 2005 24.09.2005 1 Covariant density functional theory for collective excitations in nuclei far from stability Peter Ring Kazimierz Dolny, Sept. 24, 2005 Technische Universität München
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Covariant density functional theory for collective excitations in nuclei far from stability
Covariant density functional theory for collective excitations in nuclei far from stability. Kazimierz Dolny, Sept. 24, 2005. Peter Ring. Technische Universität München. Rotional Excitations. Vibrational Excitations. Content. Covariant Density Functional Theory. - PowerPoint PPT Presentation
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XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 1
Covariant density functional theory for collective excitations
in nuclei far from stability
Covariant density functional theory for collective excitations
in nuclei far from stability
Peter Ring
Kazimierz Dolny, Sept. 24, 2005
Technische Universität München
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 2
ContentContent
Covariant Density Functional Theory
Rotional Excitations
* Parametrization of the Lagrangian
* Giant resonances GMR und GDR* Pygmy-resonances PDR* pn-QRPA and spin-isospin modes: IAR, GTR
Vibrational Excitations
* Superdeformed band in Hg-region
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 3
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 31
Spin-Isospin Resonances: IAR - GTRSpin-Isospin Resonances: IAR - GTR
Z,N Z+1,N-1
isospin flip
NZ, NZ,T IAR
spin flip
NZ,TS GTR -
r-rskin neutrondrdV
slEE pnIARGTR ~ ~ ~ - p n
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 32
Spin-Isospin Resonances: IAR and GTR
Spin-Isospin Resonances: IAR and GTR
proton-neutron relativistic QRPA
charge-exchange excitations
π and ρ-meson exchange generate the spin-isospin dependent interaction terms
the Landau-Migdal zero-range force in the spin-isospin channel
GAMOW-TELLER RESONANCE:
ISOBARIC ANALOG STATE:
S=1 T=1 J = 1+
S=0 T=1 J = 0+
(g’0=0.55)
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 33
GTR GT-ResonancesGT-Resonances
N. Paar, T. Niksic, D. Vretenar, P.Ring, PR C69, 054303 (2004) experiment
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 34
IARIsobaric Analog Resonance: IARIsobaric Analog Resonance: IAR
N. Paar, T. Niksic, D. Vretenar, P.Ring, PR C69, 054303 (2004)
experiment
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 35
Neutron skin and IAR/GRTNeutron skin and IAR/GRT
The isotopic dependence of the energyspacings between the GTR and IAS
direct information on the evolution of the neutron skinalong the Sn isotopic chain
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 36
* Important points: - the tail of the GT-strength distribution at low energies - the position of specific single particle levels (i.e. effective mass) - effective pairing force in the T=1 and T=0 channel. - in simple QRPA the lifetimes are too big
allowed β-decay :allowed β-decay :
* Possible methods to improve the results:- coupling to surface vibrations (difficult and beyond mean field) - use of a tensor coupling in the ω-channel (one phenom. param.)- T=0 pairing force with Gaussian character (one phen. parameter)
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 37
enhanced value of the effective mass
increased density of statesaround the Fermi surface
T. Niksic et al, PRC 71, 014308 (2005)
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 38
nonrelativistic mean-fieldmodels
relativistic mean-fieldmodels
m*/m=0.8 ± 0.1
Dirac mass: mD=m+S(r)
effective mass: m*=m-V(r)
effective mass:
conventional RMF models
spin-orbit splittings + nuclear matter binding
0.55m ≤ mD ≤ 0.60m
0.64m ≤ m* ≤ 0.67m
small density of states-> overestimated -decaylifetimes
m* represents a measure of the density of states around the Fermi surface
The nucleon effective mass m*:The nucleon effective mass m*:
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 39
The spin-orbit potential originates from the addition of two large fields: the field of the vector mesons (short range repulsion), and the scalar field of the sigma meson (intermediate attraction).
weakening of the effective single-neutron spin-orbit potential in neutron-rich isotopes
Radial dependenceof the spin-orbit term of the single neutron potential
Energy splittings between spin-orbit partner states
Lalazissis, Vretenar, Poeschl, Ring, Phys. Lett. B418, 7 (1998)
reduced energy spacings betweenspin-orbit partners
Reduction of the spin-orbit in neutron-rich nucleiReduction of the spin-orbit in neutron-rich nuclei
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 40
DD-ME1 DD-ME1*
mD/m 0.58 0.67
m*/m 0.66 0.76
tensor omega-nucleon coupling enhances the spin-orbit interaction
scalar and vector self-energiescan be reduced
T. Niksic et al, PRC 71, 014308 (2005)
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 41
Cadmium isotopes: 1g9/2 level is partially emptyT=0 pairing has large influence on the 1g7/2->1g9/2
transitionwhich dominates the -decay process
T. Niksic et al, PRC 71, 014308 (2005)
N≈82 region:N≈82 region:
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 42
An increase of the T=0 pairing partially compenstates for the fact thatthe density of states is still rather low
h9/2->h11/2G. Martinez-Pinedo and K. Langanke,
PRL 83, 4502 (1999)
T. Niksic et al, PRC 71, 014308 (2005)
XII. International Workshop Maria and Pierre Curie, Kazimierz Dolny, 200524.09.2005 43
ConclusionsConclusions
Covariant density functionals are adjusted to ground state properties of finite nuclei.
Time-dependent mean field theory provides a parameter-free theory for excited states - rotational spectra (cranked RHB-theory) - vibrational excitations (rel. quasiparticle RPA)