Lu Guo

University of Chinese Academy of Sciences, Beijing

Fusion and quasifission dynamics

in the synthesis of superheavy elements

China-Japan collaboration workshop,

Tsukuba University, 26-28 June, 2017

ContentsI. Introduction

background for SHE and TDHF

II. Fusion and quasifission dynamics

neutron-rich target 48Ca+239Pu and 48Ca+244Pu

III. Multi-nucleon transfer reaction

production of new neutron-rich isotopes

IV. Summary and perspectives

Synthesis of SHE

238U fission product

MNT reaction product

existence of long-lived SHE island?

Ways to synthesize heavy and superheavy elements: neutron capture:

94Pu---100Fm;

light ions (1H, 2H, 3H, He) colliding on target:

heaviest to 101Md

multi-nucleon transfer (MNT)

fusion reactions

cold fusion: with 208Pb and 209Bi as target, to 113Nh

hot fusion: with 48Ca as projectile, to 118Og

The synthesized SHE are neutron-deficient and

far from the predicted stable SHE island.

projectile

target

HIC with heavy nuclei

projectile

targetcapture

HIC with heavy nuclei

projectile

targetcapture

quasifission

fusion

HIC with heavy nuclei

projectile

targetcapture

quasifission fission

superheavyelement

survivalfusion

deexcitation of neutron

HIC with heavy nuclei

the time for quasifission ~10-20s, fusion-fission ~10-20 ~10-16s

Quasifission is the primary mechanism to prevent the formation of superheavy elements.

projectile

targetcapture

quasifission fission

superheavyelement

survivalfusion

deexcitation of neutron

HIC with heavy nuclei

Fusion probability

The PCN given by phenomenological model is different by several order;

The PCN can’t be measured directly in experiments;

Microscopic model would be better;

Phenomenological model DNS Langevin-type equation fusion by diffusion model Grazing model ......

Microscopic model QMD TDHF ......

time-dependent Hartree-Fock (TDHF) theory

10

Time-dependent Hartree-Fock theory

2

1 1

1 2

( ) | | ( )

1(r , , , , ) det ( , t)!

A At

t i ijti i j

A i

S t H i t dt H t v

r r t r i htAλ

λ λϕϕ ϕ

= <

= Ψ − ∂ Ψ = +

∂Ψ = =

∂

∑ ∑∫

，

，

Advantages： Fully microscopic, parameter-free theory in heavy-ion collisions;

Nuclear structure and reactions in a unified framework (same EDF);

Dynamical and quantum effects are automatically incorporated;

Limitations： Only one-body dissipation;

tunneling effect is missing;

Ef

Energy density functional (EDF)

Both time-even and time-odd EDF have been included

TDHF EDF in fusion dynamics

H0 is basic functional used in Sky3D code and most TDHF calculations

Quasifission dynamics in experiments

An experiment measure the fragment’s mass-angle correlations in 40,48Ca +238U；

The studies show an unexpected interplay between the orientation of

the prolate deformed 238U with quantum shell effects.

Quasifission dynamics in experiments

An experiment measure the fragment’s mass-angle correlations in 40,48Ca +238U；

TDHF calculations show that for 48Ca projectiles the quasifission is substantially

reduced in comparison to the 40Ca case. This partly explains the success of

superheavy element formation with 48Ca beams；

ContentsI. Introduction

background for SHE and TDHF

II. Fusion and quasifission dynamics

neutron-rich target 48Ca+239Pu and 48Ca+244Pu

III. Multi-nucleon transfer reaction

production of new neutron-rich isotopes

IV. Summary and perspectives

Experimental Synthesis of SHE 114

Experimental Synthesis of SHE 114

Experimental Synthesis of SHE 114

Experimental Synthesis of SHE 114

Experimental Synthesis of SHE 114

Experimental Synthesis of SHE 114

Zagrebaev et al., PRC85,014608(2012);

Adamian et al., PRC69,014607(2004);

TDHF studies of fusion and quasifission48Ca+239Pu with Ecm=204.02 MeV, b=2.5 fm

TDHF studies of fusion and quasifission48Ca+244Pu with Ecm=216.76 MeV, b=2.0 fm

TDHF studies of fusion and quasifission48Ca+239Pu

(1) Collisions with the tip of 239Pu produce

quasifission fragments, while collisions

with the side result in fusion；

(2) contact time decreases as b;

(3) tip: 32Ge+82Pb

side: 40Zr+74W;

(4) The interplay between quantum shell effect

and orientation of deformed nuclei;

TDHF studies of fusion and quasifission48Ca+239Pu 48Ca+244Pu

TDHF studies of fusion and quasifission48Ca+239Pu 48Ca+244Pu

(1) The collision 48Ca+239Puis much easier to happen quasifission than 48Ca+244Pu (experiment),

(2) More neutron-rich target nucleus will be helpful in the production of SHE(ANU experiments);

(3) PCN=σfus/σcap , PCN=0.2 2(48Ca+244Pu), PCN=0.14 (48Ca+239Pu)---side (first microscopic PCN);

TDHF studies of fusion and quasifission

Mass-angle distribution: directly measured by experiments

in TDHF outθ θ θ θ= + +

TDHF studies of fusion and quasifission

Mass-kinetic distribution: directly measured by experiments

Systematic agreement with the Viola formula;

Quasifission dynamics is a fully damped motion;

ContentsI. Introduction

background for SHE and TDHF

II. Fusion and quasifission dynamics

neutron-rich target 48Ca+239Pu and 48Ca+244Pu

III. Multi-nucleon transfer reaction

production of new neutron-rich isotopes

IV. Summary and perspectives

德国GSI

日本KEK

Multi-nucleon transfer reaction

美国Argone

俄罗斯DUBNA

The experiments via multi-nucleon transfer reaction to produce neutron-rich heavy nuclei

30

154 150

154 154

Sm Nd 122

Sm Sm 124

+ →

+ →

fusion diffusion

0.6 pb

model

σ ∼

1310 pb σ −∼

31Ning Wang and Lu Guo, Phys. Lett. B760, 236 (2016).

Neutron-rich isotopes production New neutron-rich isotope production via multi-nucleon transfer

154 160Sm Gd 126+ →?

32Ning Wang and Lu Guo, Phys. Lett. B760, 236 (2016).

Neutron-rich isotopes productionIsotope distribution at different impact parameters

Summary

Three-dimensional TDHF with full Skyrme functional and without

any symmetry restrictions;

The fusion and quasifission dynamics in 48Ca+239Pu and 48Ca+244Pu;

Our results qualitatively explains the experimental observations;

Multi-nucleon transfer reactions produce the new neutron-rich nuclei;

Summary

Three-dimensional TDHF with full Skyrme functional and without

any symmetry restrictions;

The fusion and quasifission dynamics in 48Ca+239Pu and 48Ca+244Pu;

Our results qualitatively explains the experimental observations;

Multi-nucleon transfer reactions produce the new neutron-rich nuclei;

Thank you for your attention!

35

Quantum Molecular Dynamics Model

( )( )2

3/4 22

1( ) exp42

,

ii i

rr

i ii i

r r ir r p

H Hr Pp r

φσπσ

−= − + ⋅

∂ ∂

= = −∂ ∂

Quantum Molecular dynamics (QMD)

Advantages Microscopic theory in heavy-ion collisions;

Both mean field and collision terms inlcuded;

Limitations Pauli principle

Shell effects

antisymmetrization of wave functions

projectile

targetcapture

quasifission fission

superheavyelement

survivalfusion

deexcitation of neutron

transferor DIC

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