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

Fusion, Fragmentation and Fission Multinucleon Transfer ?

Figure: courtesy R. Knöbel

Deep Inelastic Transfer Reactions

Nuclear Molecule

FUSION DEEP INELASTIC TRANSFER

E* = E cm – TKE + Q Primary Transfer Products Evaporation Residue (ER) Compound Nucleus

FUSION-FISSION

Fission Fragments Evaporation Residue (ER)

σ ER = σ capture ∙ P prim ∙ P survival

Fission Fragments

Theoretical Model Predictions

Population of nuclei along the N = 126 shell in transfer reactions

→ Application of neutron-rich projectiles and targets in the Pb region → Application of beam energies at the Coulomb barrier

adiabatic potentials

136 Xe + 208 Pb

DNS model 1 μb 1 μb

A Ni + 198 Pt

V. Zagrebaev, W. Greiner, PRL 101, 122701 (2008).

Myeong-Hwan Mun, G.G. Adamian et al., PRC 89, 034622 (2014).

The small cross-sections of <1 μb require separation + single event detection

The Velocity Filter SHIP

Separation and identification of heavy reaction products at SHIP

pulsed beam structure 5 ms 15 ms N detector ≈ 100 / s N beam ≈ 5·10 12 / s ΔΘ = (0 ± 2)°; ΔΩ = 10 msr v ~ E/B Z+1 Y Z X β − γ

Isotope identification via radioactive decays

 3  2  1

E, T 1/2 E, T 1/2 E, T 1/2

sf

Population of Transfer Products along N=126 The reaction 64 Ni + 207 Pb 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 identified isotopes target nucleus, 207 Pb

Population of Transfer Products along N=126 Transfer and fragmentation cross-sections

for neutron-rich nuclei: σ Transfer ≥ σ Fragmentation

− 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.

Transfer and Fragmentation → Consideration on experimental conditions

N beam d Target angular efficiency angular distribution A, Z identification

Transfer

5 · 10 12 / s 500 μg / cm 2 <5% (SHIP) up to ~50º (Coulomb barrier) α, β decays

Fragmentation

5 · 10 9 / s 5 g / cm 2 <50% (FRS) few degree (relativistic energies) E, ΔE, TOF, Bρ only applicable for nuclei with appropriate decay properties applicable for all nuclei experimental conditions are much more favourable in fragmentation reactions

Population of Transfer Products along N=126 Transfer and Fragmentation yields (at the target)

Transfer Fragmentation N beam 5 · 10 12 / s 5 · 10 9 / s d Target 500 μg / cm 2 5 g / cm 2 efficiency < 5% (SHIP) < 50% (FRS) yield (Fragmentation) > 10 x yield (Transfer)

Population of N-rich Transuranium Isotopes

→ Transuranium nuclei are not reachable in fragmentation reactions

Transfer reactions in 48 Ca + 248 Cm studied at SHIP Detection of new isotopes is restricted by missing identification techniques

identified at SHIP 48 Ca + 248 Cm (transfer), H. Gäggeler et al., PRC 33, 1983 (1986) 238 U + 248 Cm (transfer), M. Schädel et al., PRL 48, 852 (1982)

Isotope ID via Precision Mass Measurements?

Isobar identification Penningtrap

• mass selective • T 1/2 > 100 ms • m/Δm > 10 6 - 10 7 stopping cell

Time-of-Flight spectrometer

• broad-band • T 1/2 > 10 ms • m/Δm > 10 5

(T. Dickel, W. Plaß et al., JLU Gießen)

Summary

► 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: 64 Ni + 207 Pb reactions → observation of n-rich isotopes with Z = 73 - 89 → σ Transfer ≥ σ Fragmentation but: fragmentation leads to much higher yields ▪ Z > 92: 48 Ca + 248 Cm 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