Reactions with exotic nucleiReactions with exotic nuclei( ( at FLNRat FLNR ) )

• Recent experiments on fusion of Recent experiments on fusion of 66HeHe

• Deep sub-barrier fusion of neutron rich nucleiDeep sub-barrier fusion of neutron rich nuclei

• A few words about astrophysicsA few words about astrophysics

DIRECT

10m

0

R IB

400-cm cyclotron

400-cm cyclotronradioactive ion beams

low energy beam line

7Li

DubnaRadioactive IonBeams

6He

Electronaccelerator

ISOL

Acculinna

DIRECT

Fusion, transfer and breakup reaction mechanisms induced by halo nucleus Fusion, transfer and breakup reaction mechanisms induced by halo nucleus 66HeHeJINR (Dubna), CSNSM (Orsay), IRS (Strasbourg), ULB (Bruxelles), Vanderbilt Univ. (USA)

6He + 166Er 172Yb* 166Yb + 6n

6He + 166Er 170Yb* + 2n

6He + 166Er 168Er* + 4He

166Er(6He,6n)166Yb & 165Ho(6Li,5n)166Yb <==> 166Er(4He,4n)166Yb //PRC48(1993)319//3 2 1

DRIBsDec.- January ’07U400

6He + 166Er → 172Yb* → 166Yb + 6n → 167Yb + 5n → 170Yb*+2n → 168Yb + 4n → 168Er* + α → 168Er

Complete & incomplete fusion reactions with 6He (Complete & incomplete fusion reactions with 6He (E=62 MeVE=62 MeV))

Data analysis using EMPIRE-II code http://www.nndc.bnl.gov/nndcscr/model-codes/empire-ii/

The statistical model used in the EMPIRE-II is an advanced implementation of the Hauser-Feshbach theory. The exact angular momentum and parity coupling is observed. The emission of neutrons, protons alpha-particles and light ion is taken into account along with the competing fission channel. The full gamma-cascade in the residual nuclei is considered.

4n5n 6n

6n

5n4n

B(6He+Er) = 16 MeV, B(6Li+Ho) = 26 MeV

EMPIER-II calculation of EMPIER-II calculation of xnxn and and fusfus

At well-above barrier energies there is no difference between 6He and 6Li from the point of view of the fusion probability.

Other reaction channels are still under analysis.

Sub-barrier fusion of Sub-barrier fusion of 66HeHe

M.S. Hussein, M.P. Pato, L.F. Canto and R. Donangelo, Phys.Rev. C 46, 377 (1992).L. F. Canto, R. Donangelo, P. Lotti and M.S. Hussein, Phys.Rev. C 52, R2848 (1995).N. Takigawa and H. Sagawa, Phys.Lett. B 265, 23 (1991).C.H. Dasso and A. Vitturi, Phys.Rev. C 50, R12 (1994).K. Hagino, A. Vitturi, C.H. Dasso and S.M. Lenzi, Phys.Rev. C 61, 037602 (2000).A.S. Fomichev et al., Z.Phys. A 351, 129 (1995).J.J. Kolata et al., Phys.Rev.Lett. 81, 4580 (1998).M. Trotta, J.L. Sida, N. Alamanos et al., Phys.Rev.Lett. 84, 2342 (2000).R. Raabe, J.L. Sida, J.L. Charvet et al., Nature 431, 823 (2004).A. Di Pietro et al., Phys. Rev. C 69, 044613 (2004).A. Navin et al., Phys. Rev. C 70, 044601 (2004).C. Beck, N. Keeley, and A. Diaz-Torres, Phys. Rev. C 75, 054605 (2007).…

Neutron excess itself does not play an important roleNeutron excess itself does not play an important role

Neutron transfer with positive Q-value is important !Neutron transfer with positive Q-value is important !

Sub-barrier fusion enhancement due to neutron transferSub-barrier fusion enhancement due to neutron transfer( sequential fusion, “energy lift” )( sequential fusion, “energy lift” )

Wave functions of valence neutrons spread over both nuclei before they reach and overcome the Coulomb barrier

Time dependent Time dependent Schrödinger equationSchrödinger equation

( Zagrebaev, Samarin & Greiner, PRC 2006)

Proposed experimentsProposed experiments

First experimentFirst experiment

MSP-144

Focal plane

Ionizationchamber

Reactionchamber

Si-detectors

Strip-detector

Au-targets

Monitors

Monitor

SETUP FOR ACTIVATION MEASUREMENTS with MSP-144

dE/dx~40keV/mm

target~20mm

E ~ 0.4MeV

Huge enhancement Huge enhancement in deep sub-barrier fusion of weakly bound nucleiin deep sub-barrier fusion of weakly bound nuclei

Fusion of light neutron rich and stable nucleiFusion of light neutron rich and stable nuclei

Light neutron rich nuclei in astrophysical nucleosynthesis ?Light neutron rich nuclei in astrophysical nucleosynthesis ?

in particular,in particular,

instead of the bottle-neck three-body reaction

4He + 4He (→8Be, 10-16s ) + 4He → 12C,

4He + 6He(1s) → 9Be + n probably may occur.

Fusion of light neutron rich nuclei produced in the r-process Fusion of light neutron rich nuclei produced in the r-process may significantly change the nucleosynthesis scenario ?may significantly change the nucleosynthesis scenario ?

Experiments which could be performedExperiments which could be performed

• 11HH((66He,nHe,nγγ))66LiLi

• 33HeHe((66He,2nHe,2nγγ))77BeBe

• 66LiLi((66He,nHe,nγγ))1111BB

• 99BeBe((66He,2nHe,2nγγ))1313CC

• 1010BB((66He,2nHe,2nγγ))1414NN

• 1212CC((66He,2nHe,2nγγ))1616OO

• 1414NN((66He,2nHe,2nγγ))1818FF

• ……

• 11HH((99Li,nLi,nγγ))99BeBe

• 33HeHe((99Li,2nLi,2nγγ))1010BB

• 66LiLi((99Li,2nLi,2nγγ))1313CC

• 99BeBe((99Li,2nLi,2nγγ))1616NN

• 1010BB((99Li,3nLi,3nγγ))1616OO

• 1212CC((99Li,2nLi,2nγγ))1919FF

• 1414NN((99Li,2nLi,2nγγ))2121NeNe

• ……

Reactions withReactions with 66HeHeReaction Barrier Energy (c.m.)

lab.Q (MeV) Reaction channels Gamma-lines

6He + p → 7Li 0.4 (0.2 – 0.5)1.4 – 3.5

+10 1H ( 6He, 7Li γ)1H ( 6He, 6Li n γ)

6Li: 3.6, 0+ 2.2, 3+

g.s., 1+

6He + 3He → 9Be 0.8 (0.4 – 1.2)1.2 – 3.6

+21 3He ( 6He, 8Be n γ)3He ( 6He, 7Be 2n γ)

6He + 6Li → 12B 1.0 (0.5 – 1.5)1.0 – 3.0

+18 6Li ( 6He, 11B n γ)6Li ( 6He, 10B 2n γ)

10B: 2.2, 1+ 1.7, 0+ 0.7, 1+

g.s., 3+

6He + 9Be → 15C 1.3 (0.6 – 1.6)1.0 – 2.7

+19 9Be ( 6He, 14C n γ)9Be ( 6He, 13C 2n γ)

6He + 10B → 16N 1.6 (0.8 – 2.4)1.3 – 3.8

+24 10B ( 6He, 15N n γ)10B ( 6He, 14N 2n γ)

6He + 12C → 18O 1.9 (1.0 – 3.0)1.5 – 4.5

+18.4 12C ( 6He, 17O n γ)12C ( 6He, 16O 2n γ)

16O: 6.9, 2+ 6.1, 3- 6.0, 0+ g.s., 0+

6He + 14N → 20F 2.2 (1.1 – 3.1)1.6 – 4.5

+20.5 14N ( 6He, 19F n γ)14N ( 6He, 18F 2n γ)

6He + 16O → 22Ne 2.5 (1.2 – 3.3)1.7 – 4.5

+20.9 16O ( 6He, 21Ne n γ)16O ( 6He, 20Ne 2n γ)

Reactions withReactions with с с 99LiLi

Reaction Barrier Energy (c.m.)lab.

Q (MeV) Reaction channels Gamma-lines

9Li + 3He → 12B 1.2 (0.5 – 1.2)2.0 – 4.8

+26.5 3He ( 9Li, 10B 2n γ) 10B: 2.2, 1+ 1.7, 0+ 0.7, 1+

g.s., 3+

9Li + 6Li → 15C 1.5 (0.7 – 1.5)1.7 – 3.7

+29.1 6Li ( 9Li, 13C 2n γ)6Li ( 9Li, 11Be + 4He)

13C: 3.9, 5/2+ 3.7, 3/2- 3.1, 1/2+ g.s., 1/2-

9Li + 10B → 19O 2.4 (1.1 – 2.4)2.1 – 4.7

+33.7 10B ( 9Li, 17O 2n γ)10B ( 9Li, 15C + 4He)

9Li + 14N → 23Ne 3.3 (1.5 – 3.3)2.5 – 5.5

+33.0 14N ( 9Li, 21Ne 2n γ)14N ( 9Li, 19O + 4He)

Standard scenario Standard scenario for nucleosynthesisfor nucleosynthesis

Уровни Уровни 77LiLi и и 99BeBe