Beta-decay of very neutron-rich nuclei in N=126 region I.N.Borzov, - PowerPoint PPT Presentation

Beta-decay of very neutron-rich nuclei in N=126 region I.N.Borzov, K.Langanke, G.Marti’nez-Pinedo, A.Arcones GSI, D-64291,Darmstadt, Germany Continuum QRPA framework based on the self-consistent g.s. from EDF theory. DF+CQRPA A quest for spin-current part of (universal) NDF Nuclear structure at the limit of a high (N-Z). Important applications: RNB experiments on beta-decay of short-lived neutron-rich nuclei. � Astrophysical R-process modeling (masses, beta-rates, (n, γ )- rates…). � Accelerator Driven Systems (1GeV p + 208Pb and 238U targets). �

GSI experiments near N=126 GSI 2007 GSI 2007 8 nuclides: 75 Re, 76 Os, 77 Ir Ir … … 8 nuclides: 75 Re, 76 Os, 77 Colour scale: the known half Colour scale: the known half- -lives ( lives (NuBase NuBase). ). . exp.0711.0101v1 . Circles: T. Kurtukian Circles: T. Kurtukian- -Nietto Nietto , , J.Benlliure J.Benlliure et al. Nucl et al. Nucl- -exp.0711.0101v1 Empty boxes: identified with no half- -life information. life information. Empty boxes: identified with no half GSI 2010 GSI 2010 213Tl , 221,222 Po, 224At, 236Ac 213Tl , 221,222 Po, 224At, 236Ac L. Chen et al. Nucl- L. Chen et al. Nucl -exp.0110. exp.0110. Identified with the half- -life information life information Identified with the half Large-scale explorations of the nuclear mass-surface and beta-decay “ landscape”. Gamow-Teller vs first-forbidden decays near closed shell N=126

EDF . Self-Consistent Ground State ⎛ ⎞ − μ − Δ ⎛ ⎞ 2 h p ⎜ ⎟ = ⎜ ⎟ ρ ν = ρ + ρ ν H ⎜ ⎟ E [ , ] Tr E [ , ] − ⎜ ⎟ Kohn Sham int − Δ μ − ⎝ ⎠ h 2 M ⎝ ⎠ δ 2 p E = + ρ 1 h ~ ∑ = ε ρ + ν ξ ρ ν δ ρ E [ ] * F [ ] 2 m int n 2 main Coul sl , , δ ∝ + E " main " volume fin range surface . Δ = int δν ξ ∝ + F volume surface ρ ν ⇒ Δ ⇒ ρ ν ⇒ Δ , h , , h , 0 0 0 0 1 1 1 1 � Energy Density functional S.A. Fayans, S.V. Tolokonnikov,E.Trykov, D. Zawischa, Nucl.Phys. A676 (2000) 49. I.N. Borzov, S.A. Fayans, E. Kromer, D. Zawischa Z. Phys. A335(1996) 117 DF3 � Fenomenological (local) energy-density functional by S.A. Fayans et al., δ -function + density dependent (volume+surface) pairing. Fitted to the g.s. properties of very neutron-rich nuclei near “magic cross” Z=50/N=82 at 132 Sn.

CQRPA. Effective spin-isospin NN-interaction δ δ 2 2 E E ω = ξ = F F ττ ττ τ τ τ τ δρ δρ δν δν The ground state properties are less sensitive to spin-isospin components of EDF. The spin-isospin (time odd) parts of the effective NN-interaction can be defined independently of the scalar (time-even) parts. Continuum QRPA based on the self-consistent ground state. Universal effective NN-interaction (A-independent). 2 =(0.9) 2 (A, E-independent). Universal quenching e q T=1, ph T=0, pp ξ ∝ δ − ω ∝ δ + π + ρ ' F g ' pp F g ττ ττ − r r ' r r ' LM

Q β – values: maximal beta-decay energy releases Accurate description of the Q β -values is crucial for beta-decay studies. Q β is correlated with the qp-energies, as both are obtained from the same DF framework. DFs with m*/M~1 reproduce Q β –values well enough : For N=82 Typical deviation from the data is 0.5 - 1.5 MeV For N=126 Deviation is 0.5 - 0.6 MeV (Recent RDFs underestimate the phase-space, overshooting T1/2) Extended mass measurements at N=126 are of high value for improving the DF oving the DF Extended mass measurements at N=126 are of high value for impr

Possible improvements : Spin-orbital part of the Df3 Example: Qbeta-values sensitivity to the velocity dependent interaction (g1 np ) 10 Q β, DF3 Q β ,MeV Q β, DF3* 4 Pb isotopes Exp.data Q β ,MeV Audi est. 8 6 2 4 DF3 DF3* Exp.data 2 0 Tl isotopes 0 208 210 212 214 216 218 220 222 204 208 212 216 220 224 A A Spin-orbital splitting needs re-adjustment in a wide A-region (especially for the nuclei with high spin-orbital density , Z=80-90 region)

The GT and FF strength-functions are calculated within the single DF3+CQRPA framework 202Ir 6 4 202Ir GT GT log (f 0 t i ) FF FF GT log (f 0 t i ) J=1 n1h9/2 n1h9/2 � � p1h11/2 p1h11/2 4 T GT = 0.2255E+06 s n1i13/2 � � p1h11/2 p1h11/2 n1i13/2 T GT+J=1 = 22.05 s 2 2 n3p3/2 � n3p3/2 � p3d3/2 p3d3/2 0 0 0 1 2 3 4 5 n3p1/2 � � p3s1/2 p3s1/2 n3p1/2 Ex , MeV Ex , MeV 202Ir log (f 0 t i ) 6 J=0 Qb=4.37MeV T GT+J=1+J=0 =9.8 s 4 Q β 2 0 0 1 2 3 4 5 Ex , MeV The GT decays are retarded by The GT decays are retarded by - the low the low “ “phase phase- -space space” ” factors factors f(Qb f(Qb- -Ex) Ex) - - high occupancy factor of the high occupancy factor of the 1ph11/2 orbital. 1ph11/2 orbital. - The high- The high -energy FF decays compete with the low transition energy GT de energy FF decays compete with the low transition energy GT decays cays. .

72Hf – 78Pt. Half-lives approaching N=126 Typical deviation from the exp. data 100 10 DF3+CQRPA FRDM+Gr.Th. Gr.Th. FRDM = 30 T1/2, s 10 1 DF3 = 1 - 2 1 0,1 ___________________________________ 72 Hf 74 W 0,1 0,01 A,Z T1/2 (s) DF3 FRDM 184 186 188 190 192 194 196 198 200 196 198 200 202 204 206 208 A A 199Os 5 +4-2 6.6 106.8 DF3+CQRPA DF3+CQRPA FRDM+Gr.Th. 200Os 6+4-3 6.9 187.1 1000 .Expt.GSI_2007 Gr.Th. FRDM+Gr.Th. ___________________________________ 100 Expt. GSI_ 2007 Gr. TH. Expt. NuBase T1/2, s 100 10 New GSI FRS-ESR campaigns 10 1 TRIAC, KEK Japan, Proposal 09 1 0,1 These Proposals are aimed to pin down 0,1 76 Os 78 Pt the r-process waiting point nuclei 0,01 0,01 194 196 198 200 202 204 206 202 204 206 208 210 212 214 216 198Hf, 200W, 202Os, 204Pt A A

73Ta – 79Au. Half-lives of odd-Z nuclides approaching N=126 DF3+CQRPA 100 10000 DF3+CQRPA Exp. NuBase Typical deviation from the exp. data Exp. 2007 FRDM+Gr.Th. FRDM+Gr.Th. Gr.Th. 1000 T1/2, s 10 Gr.Th. FRDM = up to 70 100 1 DF3 = up to 8 10 1 ___________________________________ 0,1 73 Ta 0,1 75 Re A,Z T1/2 (s) DF3 FRDM 0,01 0,01 188 190 192 194 196 198 200 202 204 206 190 192 194 196 198 200 202 204 206 208 210 A A 194Re 1 +- 0.5 2.1 70.8 195Re 6+-1 8.5 3.3 10000 DF3+CQRPA Exp. 2007 100 FRDM+Gr.Th. 1000 196Re 3+1-2 1.4 3.6 DF3+CQRPA Gr.Th. T1/2, s FRDM+Gr.Th ___________________________________ Exp.NuBase. 100 10 Gr.Th. 10 1 205Au 1 Exp. 31+/- 2 (s) 79 Au 77 Ir 0,1 0,1 200 202 204 206 208 210 212 214 216 218 220 198 200 202 204 206 208 210 212 214 A A FRDM = 221,0 s (7) DF3 = 18.7 s (1.6)

64Gd isotopes near N=126. DF3+CQRPA T1/2, s FRDM 0,01 64Gd 1E-3 186 188 190 A 192 194 196 198 100 80 Pn, % 60 “saturation “ saturation- -like like” ” 40 20 0 186 188 190 192 194 196 198 A 16 Q β n ω, MeV 14 ω GT 12 ω 1 10 ω 0 8 Q β 6 4 186 188 190 192 194 196 198 A

67Ho,69Tm isotopes near N=126. Z=67, 69, N ~ 126 DF3+CQRPA DF3+CQRPA FRDM FRDM 0,1 0,1 T1/2, s T1/2, s 0,01 Ho Tm 0,01 188 190 192 194 196 198 200 186 188 190 192 194 196 198 200 202 A A 100 90 90 80 80 70 70 Pn, % Pn, % 60 60 50 50 40 40 30 “ “gap gap- -like like” ” 30 20 20 10 10 0 188 190 192 194 196 198 200 186 188 190 192 194 196 198 200 202 A A

N=126 waiting point nuclei 0,1 0,01 T1/2, s DF3+CQRPA GT GT+FF SM(2) GT FRDM+gt 1E-3 N=126 GT+FF 60 62 64 66 68 70 A 1000 T1/2, s 100 SM(1) SM(2) 10 DF3+CQRPA GT GT+FF 1 FRDM+gt GT+FF N=126 0.1 exp. NuBase 70 72 74 76 78 80 82 Z

Impact of the half-lives on R-process abundances at N=126 (A.Arcones e.a. 2010) FRDM half FRDM half- -lives were replaced by the DF3 ones lives were replaced by the DF3 ones Changes the abundances near the third peak (A~195) Changes the abundances near the third peak (A~195) for the nuclides near N=126 only. and for fissioning fissioning nuclei nuclei for the nuclides near N=126 only. and for Hot Cold r- -process process Hot Cold r

I. Summary (Beta-decay) Global calculations of the β -decay half-lives. � Systematic studies in a wide (Z=15 – 92) region: Table I. Spherical nuclei. Used for new experiments at GSI, KEK, HRIBF GT decay dominates for Z~ 28, 50 for N<N mag =50, 82 � Competition of GT and high-energy FF decays for heavier Z = 60 - 82 , N approaching Nmag=126 . Signatures of the GT/FF competition: “saturation-like” and � “saw-like’ patterns in Pn(A) behavior . The shorter half-lives make evolution faster , break through � the N=126 waiting points faster. The matter flow to heavier (fissioning) nuclei should be also faster in DF3+CQPRA. .