multinucleon transfer reactions – a new way to exotic nuclei? sophie heinz gsi helmholtzzentrum...
TRANSCRIPT
Multinucleon Transfer Reactions –
a New Way to Exotic Nuclei?
Sophie Heinz
GSI Helmholtzzentrum and
Justus-Liebig Universität Gießen
Trento, May 26 - 30, 2014
Synthesis of Exotic Nuclei
Figure: courtesy R. Knöbel
Multinucleon Transfer ?
Fusion, Fragmentation and Fission
Deep Inelastic Transfer Reactions
FUSION
DEEP INELASTIC TRANSFER
Nuclear Molecule
Compound Nucleus
EvaporationResidue (ER)
FUSION-FISSION
FissionFragments
σER = σcapture ∙ Pprim ∙ Psurvival
EvaporationResidue (ER)
FissionFragments
Primary Transfer Products
E* = Ecm – TKE + Q
Population of nuclei along the N = 126 shell in transfer reactions
1 μb
The small cross-sections of <1 μb require separation + single event detection
136Xe + 208Pb
Theoretical Model Predictions
→ Application of neutron-rich projectiles and targets in the Pb region→ Application of beam energies at the Coulomb barrier
Myeong-Hwan Mun, G.G. Adamian et al.,PRC 89, 034622 (2014).
V. Zagrebaev, W. Greiner, PRL 101, 122701 (2008).
ANi + 198Pt
1 μb
DNS modeladiabatic potentials
The Velocity Filter SHIP
Nbeam ≈ 5·1012 / s
Ndetector ≈ 100 / s
v ~ E/B1
2
sf
3
E, T1/2
E, T1/2
E, T1/2
Isotope identification via radioactive decays
Separation and identification of heavy reaction products at SHIP
5 ms
15 ms
ΔΘ = (0 ± 2)°; ΔΩ = 10 msr
pulsed beam structure
β−
γ
ZX
Z+1Y
Population of Transfer Products along N=126
identified isotopes
target nucleus, 207Pb
The reaction 64Ni + 207Pb at 5.0 MeV/u studied at SHIP
→ Isotope identification via gamma spectroscopy in the focal plane of SHIP→ identificaiton of isotopes with Z = 73 – 89 with cross-sections >10 μb
for neutron-rich nuclei: σTransfer ≥ σFragmentation
− SHIP exp.: S. Heinz, O. Beliuskina, proceedings of the ECHIC2013, Jour. Conf. Ser. 515, (2014) 012007.− [1] W. Krolas et al., Nucl. Phys. A 724 (2003) 289.
Population of Transfer Products along N=126
Transfer and fragmentation cross-sections
Transfer and Fragmentation
Transfer Fragmentation
Nbeam 5 · 1012 / s 5 · 109 / s
dTarget 500 μg / cm2 5 g / cm2
angular efficiency <5% (SHIP) <50% (FRS)
angular distribution up to ~50º(Coulomb barrier)
few degree(relativistic energies)
A, Z identification α, β decays E, ΔE, TOF, Bρ
→ Consideration on experimental conditions
only applicable for nucleiwith appropriate decayproperties
applicable forall nuclei
experimental conditions are much more favourable in fragmentation reactions
Population of Transfer Products along N=126
Transfer and Fragmentation yields (at the target)
Nbeam dTarget efficiency
Transfer
Fragmentation
5 · 1012 / s
5 · 109 / s
500 μg / cm2
5 g / cm2
< 5% (SHIP)
< 50% (FRS)
yield (Fragmentation) > 10 x yield (Transfer)
Population of N-rich Transuranium Isotopes
Transfer reactions in 48Ca + 248Cm studied at SHIP
→ Transuranium nuclei are not reachable in fragmentation reactions
identified at SHIP
48Ca + 248Cm (transfer), H. Gäggeler et al., PRC 33, 1983 (1986) 238U + 248Cm (transfer), M. Schädel et al., PRL 48, 852 (1982)
Detection of new isotopes is restricted by missing identification techniques
Isotope ID via Precision Mass Measurements?
Penningtrap• mass selective• T1/2 > 100 ms
• m/Δm > 106 - 107
Time-of-Flight spectrometer• broad-band• T1/2 > 10 ms
• m/Δm > 105
stopping cell
(T. Dickel, W. Plaß et al., JLU Gießen)
Isobar identification
► Model calculations suggest the production of new neutron-rich nuclei in the region of Z > 92 and along N = 126 in transfer reactions → lack of experimental data
► Small cross-sections (< 1 μb) require effective separation + single event ID → lack of dedicated experimental setups → but: separators used in SHE research can be used for transfer studies
► Investigation of transfer reactions at SHIP: ▪ N = 126: 64Ni + 207Pb reactions → observation of n-rich isotopes with Z = 73 - 89
→ σTransfer ≥ σFragmentation but: fragmentation leads to much higher yields
Summary
▪ Z > 92: 48Ca + 248Cm reactions → observation of n-rich isotopes with Z = 84 – 102 → region cannot be accessed in fragmentation or fusion reactions with stable beams
► main restriction is presently missing identification techniques for heavy transfer products