Heavy ion transfer reactions studied with PRISMA+CLARA

LEA, Catania, 13-16 October, 2008

Heavy ion transfer reactions studied Heavy ion transfer reactions studied with PRISMA+CLARA with PRISMA+CLARA

Heavy ion transfer reactions studied Heavy ion transfer reactions studied with PRISMA+CLARA with PRISMA+CLARA

L.CorradiLaboratori Nazionali di Legnaro – INFN, Italy

‘

A

A’

a’

a

Transfer reactions (multinucleon) among Transfer reactions (multinucleon) among heavy ionsheavy ions

Transfer reactions (multinucleon) among Transfer reactions (multinucleon) among heavy ionsheavy ions

The quasi-elastic regime is governed by

- form factors < f I Vint I i > (structure)

- optimum Q-values (dynamics)

degrees of freedom

single particle states

surface vibrations

pair modes

couplings

inelastic: collective ff

transfer: single particle ff

pair ff (macroscopic)

The understanding of low energy heavy ion reactions requires a careful and consistent experimental and theoretical work

- elastic scattering (nuclear potential)

- inelastic scattering (phonon form factor)

- one particle transfer (single particle form factors)

- two particle transfer (nucleon-nucleon correlations)

- multiple particle transfer (multipair transfer, ... towards DIC)

mandatory a complete set of observables

A, Z, TKEL, dσ/dΩ, σtot

THE PRISMA SPECTROMETER + CLARA GAMMA ARRAY

IC

MWPPAC

A physical event is composed by the A physical event is composed by the parameters:parameters:

•position at the entrance position at the entrance x, y x, y •position at the focal plane position at the focal plane X, YX, Y•time of flight time of flight TOF TOF•energy energy DE, EDE, E

A physical event is composed by the A physical event is composed by the parameters:parameters:

•position at the entrance position at the entrance x, y x, y •position at the focal plane position at the focal plane X, YX, Y•time of flight time of flight TOF TOF•energy energy DE, EDE, E

PRISMA spectrometer – trajectory PRISMA spectrometer – trajectory reconstruction reconstruction




ΔE-E

q

A/q

Mass

Elastic scattering – using Prisma and Clara Elastic scattering – using Prisma and Clara informationinformation

Elastic scattering – using Prisma and Clara Elastic scattering – using Prisma and Clara informationinformation

elastic scattering is the first important ingredient for nuclear

reaction studies. It provides information on the (outer part

of) nuclear potential

grazing code

Differential cross Differential cross sections sections


forward part : mainly reflects the behaviour of the form factors

backward part : mainly reflects the absorption

Total cross Total cross sections sections

Total cross Total cross sections sections

successive transfer

S.Szilner et al, Phys.Rev.C76(2007)024604

multinucleon multinucleon transfer :transfer :experiment vs. experiment vs. theory theory

multinucleon multinucleon transfer :transfer :experiment vs. experiment vs. theory theory

data : LNL

theory : GRAZING code and CWKB

Evaporation processes in multinucleon transfer Evaporation processes in multinucleon transfer reactionsreactions

Evaporation processes in multinucleon transfer Evaporation processes in multinucleon transfer reactionsreactions

Evaporation processes Evaporation processes directly identified with directly identified with PRISMA+CLARA An example: PRISMA+CLARA An example: 4040Ca+Ca+9696Zr at 152 MeV Zr at 152 MeV

Evaporation processes Evaporation processes directly identified with directly identified with PRISMA+CLARA An example: PRISMA+CLARA An example: 4040Ca+Ca+9696Zr at 152 MeV Zr at 152 MeV

4040Ca+Ca+9696ZrZrE=152 MeV E=152 MeV

4040Ca+Ca+9696ZrZrE=152 MeV E=152 MeV

TKEL distributions – Prisma vs. TKEL distributions – Prisma vs. Prisma+ClaraPrisma+Clara

TKEL distributions – Prisma vs. TKEL distributions – Prisma vs. Prisma+ClaraPrisma+Clara

TKEL TKEL distributions distributions

TKEL TKEL distributions distributions

pure proton stripping

Pair Pair transfer transfer

Pair Pair transfer transfer

Search for pairing vibrations

Measurements at sub-barrier energies

How the residual interaction acts in transfer How the residual interaction acts in transfer processes processes

How the residual interaction acts in transfer How the residual interaction acts in transfer processes processes

S.Szilner et al, Eur.Phys.J. A21, 87(2004)

strength function (shell model calculations)

Strong population close to the pairing vibrational region in Strong population close to the pairing vibrational region in 4040Ca+Ca+208208PbPb

Strong population close to the pairing vibrational region in Strong population close to the pairing vibrational region in 4040Ca+Ca+208208PbPb


Multineutron and multiproton transfer channels near closed-Multineutron and multiproton transfer channels near closed-shell nucleishell nuclei

Multineutron and multiproton transfer channels near closed-Multineutron and multiproton transfer channels near closed-shell nucleishell nuclei

PRISMA spectrometer data

GRAZING code calculations

Mass [amu]

pure neutron pick-up channels

9090Zr+Zr+208208Pb EPb Elablab=560 =560 MeVMeV

9090Zr+Zr+208208Pb EPb Elablab=560 =560 MeVMeV

L.Corradi et al, Nucl.Phys.A787(2007)160

2240

1874

3308

3842

Population of states close to the Population of states close to the pairingpairing vibrational region vibrational region

Population of states close to the Population of states close to the pairingpairing vibrational region vibrational region

Sub-barrier transfer Sub-barrier transfer reactionsreactions

Sub-barrier transfer Sub-barrier transfer reactionsreactions

- few reaction channels are opened, i.e. W(r) very small

- one has a much better control on the form factors

F(r)inel has a decay length ~ 0.65 fm F(r)tr has a decay length ~ 1.3 fm nuclear couplings are dominated by transfer processes

- Q-value distributions get much narrower than at higher energies

- one can probe nucleon correlation close to the g.s.

At energies lower than the Coulomb At energies lower than the Coulomb barrier : barrier :

At energies lower than the Coulomb At energies lower than the Coulomb barrier : barrier :

data are very scarse or almost non existing

absorptive potential form factor

Q-value window

Detection of (light) target like ions in inverse kinematics with Detection of (light) target like ions in inverse kinematics with PRISMAPRISMA

Detection of (light) target like ions in inverse kinematics with Detection of (light) target like ions in inverse kinematics with PRISMAPRISMA

PRISMA

measurements have been performed for multinucleon transfer channels and at energies well below the barrier

beam direction

20o

94Zr 40Ca

SSBD (rutherford sc.)

GRAZING code calculations for GRAZING code calculations for 4040Ca+Ca+9494Zr Zr transferstransfers

GRAZING code calculations for GRAZING code calculations for 4040Ca+Ca+9494Zr Zr transferstransfers

differential cross sections

total cross sections

A.Winther, program GRAZING http://www.to.infn.it/~nanni/GRAZING

Prisma acceptance

9494Zr+Zr+4040Ca, ECa, Elablab=330 MeV, =330 MeV, θθlablab=20=20oo, inverse , inverse kinematics kinematics

9494Zr+Zr+4040Ca, ECa, Elablab=330 MeV, =330 MeV, θθlablab=20=20oo, inverse , inverse kinematics kinematics

Mass distributions for pure neutron pick-up Mass distributions for pure neutron pick-up channels channels

Mass distributions for pure neutron pick-up Mass distributions for pure neutron pick-up channels channels

TKEL distributions for pure neutron pick-up TKEL distributions for pure neutron pick-up channels channels

TKEL distributions for pure neutron pick-up TKEL distributions for pure neutron pick-up channels channels

Qgs

Mass vs Q-value matrix for (-1p) channels channels (EMass vs Q-value matrix for (-1p) channels channels (Ell=315 =315 MeV)MeV)

Mass vs Q-value matrix for (-1p) channels channels (EMass vs Q-value matrix for (-1p) channels channels (Ell=315 =315 MeV)MeV)

background free spectra with transfer products at very low excitation energy :

no evaporation effects and cleanest conditions for comparison with theory

Experimental vs Theoretical cross sections for +1n and -1p Experimental vs Theoretical cross sections for +1n and -1p channelschannels

Experimental vs Theoretical cross sections for +1n and -1p Experimental vs Theoretical cross sections for +1n and -1p channelschannels

very

pre

limin

ary

with neutron rich with neutron rich beams...beams...

with neutron rich with neutron rich beams...beams...

C.H.Dasso, G.Pollarolo and A.Winther, Phys.Rev.Lett.73, 1907 (1994)

neutron pick-up and proton stripping

equal directions

neutron stripping and proton pick-up

Change of population pattern in going from Change of population pattern in going from neutronneutron poor to neutron rich nuclei (theoretical)poor to neutron rich nuclei (theoretical)


with (moderately n-rich) heavy ions one can populate (nn), (pp) and (np) channels with comparable strength

Multinucleon transfer Multinucleon transfer reactions reactions


GRAZING code

One needs to learn whether and to what extent the degrees of freedom and the corresponding matrix elements tested with stable beams can

hold with radioactive beams. In particular whether the form factors for one and two particle transfer and their strength need to be modified

neutron-proton correlations (np channel)

Multinucleon transfer reactions with radioactive Multinucleon transfer reactions with radioactive beams beams

Multinucleon transfer reactions with radioactive Multinucleon transfer reactions with radioactive beams beams

140Snonset of supercurrents (neutron rich nuclei)

SummarSummary y

SummarSummary y

- Multinucleon transfer processes provide important information on the interplay between reaction mechanism and nuclear structure. The Prisma spectrometer coupled to large gamma arrays is a powerful tool to study the fine details of such processes.

- The degrees of freedom involved in multiple particle transfers can be quantitatively probed only when a complete set of observables (A,Z,TKEL, dσ/dΩ, σtot) is available. This is important also for the correct description of the transition from quasi-elastic to deep-inelastic regime and other competing reaction processes (e.g. sub-barrier fusion).

- Pair modes are presently being investigated looking at the decay of (possible) pair vibrational states and via extreme sub-barrier transfer of nucleons.

A.M.Stefanini, E.Fioretto, A.Gadea, B.Guiot, N.Marginean, P.Mason, R.Silvestri, G.de Angelis, D.R.Napoli, J.J.Valiente-

Dobon

Laboratori Nazionali di Legnaro – INFN, Italy

S.Beghini, G.Montagnoli, F.Scarlassara, E.Farnea, C.A.Ur, S.Lunardi, S.Lenzi, D.Mengoni, F.Recchia, F.della Vedova

Universita’ di Padova and INFN, Sezione di Padova

S.Szilner, N.Soic, D.Jelavec

Ruđer Bošković Institute, Zagreb, Croatia

G.Pollarolo

Universita’ di Torino and INFN, Sezione di Torino, Italy

F.Haas, S.Courtin, D.Lebhertz, M.-D.Salsac

IReS, Strasbourg, France

+ CLARA collaboration

R.C. Ragaini et al., PRC2(1970)1020

L=0 transitions92Zr(p,t)90Zr

86Sr(t,p)88Sr

Pairing vibrations : light ion Pairing vibrations : light ion reactions reactions

Pairing vibrations : light ion Pairing vibrations : light ion reactions reactions

Pairing vibration Pairing vibration model model

Pairing vibration Pairing vibration model model

R.Betts et al., PRL59(1987)978

58Ni + xSn

detection of (heavy) target like ions with recoil mass detection of (heavy) target like ions with recoil mass spectrometersspectrometers

detection of (heavy) target like ions with recoil mass detection of (heavy) target like ions with recoil mass spectrometersspectrometers

RMS

measurements have been performed at subbarrier energies but for only one nucleon transfer and with very poor Q-value resolution

Absolute cross sections for one and two-nucleon transfer Absolute cross sections for one and two-nucleon transfer reactionsreactions

Absolute cross sections for one and two-nucleon transfer Absolute cross sections for one and two-nucleon transfer reactionsreactions

B.F.Bayman and J.Chen, PRC26(1509)1982

E ~ Eb

direct

successive

successive

direct

E << Eb

one+two step calculations undepredict the data by a factor ~ 2

one+two step calculations undepredict the data by 25-30%

208Pb(16O,18Og.s.)206Pb

G.Pollarolo, Phys.Rev.Lett.100,252701(2008)

Quasielastic barrier distributions : role of particle transfer Quasielastic barrier distributions : role of particle transfer channelschannels

Quasielastic barrier distributions : role of particle transfer Quasielastic barrier distributions : role of particle transfer channelschannels

sub-barrier transfer cross section measurements are important to compare with fusion cross sections in a similar energy and angular momentum range

A.M.Stefanini et al., PRC76,014610(2007)

Sub-barrier fusion of Sub-barrier fusion of 4040Ca+Ca+9494Zr Zr Interplay of phonon and transfer Interplay of phonon and transfer couplingscouplings

Sub-barrier fusion of Sub-barrier fusion of 4040Ca+Ca+9494Zr Zr Interplay of phonon and transfer Interplay of phonon and transfer couplingscouplings

2+ [2067]

2+ [2820]

2+ [1848]

2+ [3058]

0+ [4283] strong in (t,p)

2+ [3500]

0+ [2903] weak in (t,p)



2+ [934]

0+ [g.s.]

1132

1225 1463

990

934

1848

492

972

934

1742

912

439

837

1970

L=2 (t,p)

L=2 (t,p)

L=2 (t,p)

L=2 (t,p)

L=2 (t,p)

L=2 (t,p)

new

identified and known

identified but in overlap with other known

existing ?

non tabnon tab

(n,n’)

(n,n’)

208Pb(90Zr,92Zr)206Pb E=560 MeV

(4000)

(50)

(1000)

(4000)

(245)

(120)

(1100) wide peak at 893



X (channels)

A/q

(ch

anne

ls)

K.Sapotta et al., PRC31(1985)1297

linear diffusion : strong correlation between proton and neutron transfer

uncorrelated N and Z diffusion

Interpretation of massive transfer via diffusion Interpretation of massive transfer via diffusion modelsmodels

Interpretation of massive transfer via diffusion Interpretation of massive transfer via diffusion modelsmodels

the region with small energy loss is where nuclear structure

properties play a major role

Multinucleon transfer reactions : quasi-elastic Multinucleon transfer reactions : quasi-elastic regimeregime

Multinucleon transfer reactions : quasi-elastic Multinucleon transfer reactions : quasi-elastic regimeregime

pure neutron pick-up

pure proton stripping

N/Z equilibrization

Mass distributions for proton stripping channels channels Mass distributions for proton stripping channels channels (E(Ell=315 MeV)=315 MeV)

Mass distributions for proton stripping channels channels Mass distributions for proton stripping channels channels (E(Ell=315 MeV)=315 MeV)

Ar isotopes (-Ar isotopes (-2p) 2p)

Ar isotopes (-Ar isotopes (-2p) 2p)

K isotopes (-K isotopes (-1p)1p)

K isotopes (-K isotopes (-1p)1p)

background free spectra with transfer products at very low excitation energy :

no evaporation effects and cleanest conditions for comparison with theory

fusion

Correlation between reaction Correlation between reaction channelschannels

Correlation between reaction Correlation between reaction channelschannels

In the presence of couplings the energy of relative motion is not well defined. An exchange of energy from the relative motion to the intrinsic degrees of freedom takes place

quasi elastic, deep inelastic

quasi fission, [...]

Evaporation processes directly identified with Evaporation processes directly identified with PRISMA+CLARA PRISMA+CLARA an example : an example : 4040Ca+Ca+9696Zr reaction at 152 MeV Zr reaction at 152 MeV

Evaporation processes directly identified with Evaporation processes directly identified with PRISMA+CLARA PRISMA+CLARA an example : an example : 4040Ca+Ca+9696Zr reaction at 152 MeV Zr reaction at 152 MeV

heavy partner

light partner

-2p+2n

channel



E

ΔE

64Ni+238U

Elastic Elastic scatteringscattering

Elastic Elastic scatteringscattering

Inelastic Inelastic scatteringscattering

Inelastic Inelastic scatteringscattering

G.Pollarolo and A.Winther, PRC62(2000)054611


G.Montagnoli et al., EPJA15(2002)351

Transfer and fusion cross sections for Transfer and fusion cross sections for 4040Ca+Ca+90,9690,96ZrZr


H.Esbensen et al, PRC57(1998)2401

exp. neutron transfer yield coupling scheme

sub-barrier fusionnear and sub-barrier transfer

Evap.Res.

Fusion

Fusion+Deep Inel.

TransferTr+Inel

2+,3-+Multiphonon

1-dim.

5858Ni+Ni+124124SSnn

5858Ni+Ni+124124SSnn

C.L.Liang et al, PRC57(1998)2393

4040Ca+Ca+9696Zr reaction : states of Zr reaction : states of particle/hole vibration character particle/hole vibration character

4040Ca+Ca+9696Zr reaction : states of Zr reaction : states of particle/hole vibration character particle/hole vibration character

nuclear binding energies deuteron transfer (light ions)

np np correlations correlations

np np correlations correlations

R.B.Cakirli et al, PRL94,092501(2005) P.Van Isacker et al, PRL94,162502(2005)

with (moderately n-rich) heavy ions one can populate (nn), (pp) and (np) channels with comparable strength



GRAZING code

Multinucleon transfer reactions with neutron-rich Multinucleon transfer reactions with neutron-rich beams beams

Multinucleon transfer reactions with neutron-rich Multinucleon transfer reactions with neutron-rich beams beams

possibility to populate nuclei via pick-up and stripping of both

neutrons and protons

probing (nn), (pp) and (np) correlations. Important for studies

on pairing vibrations/rotations, nuclear superfluidity

C.H.Dasso, G.Pollarolo, A.Winther, PRL73(1994)1907


production of neutron rich isotopes

QE/DICQE/DICQE/DICQE/DIC

U.Schroder et al., PRC16(1977)623A.D.Hoover et al., PRC25(1982)256

L.Corradi et al, PRC63(2001)021601Rg.s. Q-values

histograms: exp.

lines: CWKB theory

Strong population close to the g.s.Q-values up to +4n channels in Strong population close to the g.s.Q-values up to +4n channels in 6262Ni+Ni+206206Pb Pb

Strong population close to the g.s.Q-values up to +4n channels in Strong population close to the g.s.Q-values up to +4n channels in 6262Ni+Ni+206206Pb Pb

Search for a possible odd-even staggering effect (pair Search for a possible odd-even staggering effect (pair modes)modes)

Search for a possible odd-even staggering effect (pair Search for a possible odd-even staggering effect (pair modes)modes)

J.Giovinazzo et al., PRL99(2007)102501

Importance of nucleon-nucleon Importance of nucleon-nucleon correlationcorrelation

Importance of nucleon-nucleon Importance of nucleon-nucleon correlationcorrelation

M.V.Ricciardi et al., NPA733(2004)299

2proton decay

Ti(238U,X) 1GeV/A

the understanding of (2p) decay and U fragmentation data requires knowledge of pair effects, similarly to low energy transfer : development of nuclear structure and reaction models is essential

The transfer components and what the Grazing code can The transfer components and what the Grazing code can computecompute

The transfer components and what the Grazing code can The transfer components and what the Grazing code can computecompute

E. Fioretto - LNL66

AGATA Dem - PRISMA Workshop - LNL, 15-16 Nov 2007

70Zn+238U450 MeV

96Zr+124Sn 575 MeV

136Xe+208Pb950 MeV

40Ar+208Pb450 MeV

Z=18

Z=30

Z=40Z=54

E/E < 2% Z/Z ~ 60 for Z=20

Energy [arb. units]

A.O.Macchiavelli et al.,Phys.Lett.B480(2000)1

May T=0 collective effects show up as a vibrational phonon ?

pairing strenght

weak collective correlations

strong collective correlations, possibility to develop a permanent deformation in gauge space

Experimental excitation spectrum for addition phonons around 56Ni

Particles identified from PRISMA in Particles identified from PRISMA in the the 4848Ca+Ca+6464Ni reaction, E=320 MeVNi reaction, E=320 MeV θθlablab=30=30oo

Particles identified from PRISMA in Particles identified from PRISMA in the the 4848Ca+Ca+6464Ni reaction, E=320 MeVNi reaction, E=320 MeV θθlablab=30=30ooDIC

QE

G.Pollarolo and A.Winther, PRC62(2000)054611


G.Montagnoli et al., EPJA15(2002)351





Total kinetic energy loss distributions in Total kinetic energy loss distributions in 4040Ca+Ca+208208Pb EPb Elablab=235 =235 MeV MeV θθlablab=84=84oo

Total kinetic energy loss distributions in Total kinetic energy loss distributions in 4040Ca+Ca+208208Pb EPb Elablab=235 =235 MeV MeV θθlablab=84=84oo

TKEL corresponding to the two-touching sphere configuration (maximal amount of energy that can be lost in binary collisions)

40S

β decay

NSCL-MSU

(1)

GANIL

(2)PRISMA/CLARA

40S

N.Marginean, Trento Workshop, 2006

X.Liang, PRC74(2006)014311

Collectivity above N=20 shell Collectivity above N=20 shell closureclosure

Collectivity above N=20 shell Collectivity above N=20 shell closureclosure

D. Sohler et al.

PRC 66(2002)054302

J.A.Wigner et al.,

PRC 64(2001)064318

36S (230MeV) + 208Pb

40Ar(205MeV) + 170Er

S

82Ge

80Zn

reliable production cross sections for exotic nuclei like the N=50 82Ge or 80Zn are mandatory when one project γ-spectroscopy experiments

Cross sections measurements Cross sections measurements 8282Se+Se+238238U U EElablab=500 MeV=500 MeV

Cross sections measurements Cross sections measurements 8282Se+Se+238238U U EElablab=500 MeV=500 MeV

74Ni

C.H.Dasso, G.Pollarolo and A.Winther, Phys.Rev.Lett.73, 1907 (1994)

neutron pick-up and proton stripping

equal directions

neutron stripping and proton pick-up



GRAZING code

possibility to explore multiple particle transfers in the pick-up and stripping of both neutrons and protons

Z,A yields - time-of-flight spectrometer data (LNL)

Total cross sections – data compared with Complex WKB calculations


N/Z of the compound

pure proton stripping pure neutron pick-up


successive transfer

+ simultaneous transfer

CWKB CALCULATIONS

Pure neutron and proton Pure neutron and proton transfers transfers

Pure neutron and proton Pure neutron and proton transfers transfers

neutronsprotons

successive transfer+ simultaneous transfer

+ evaporation effects

L.Corradi et al, PRC66(2002)024606

CWKB

CALCULATIONS

Pure neutron and proton transfers in Pure neutron and proton transfers in 5858Ni+Ni+208208Pb Pb EElablab=328.4 MeV=328.4 MeV

Pure neutron and proton transfers in Pure neutron and proton transfers in 5858Ni+Ni+208208Pb Pb EElablab=328.4 MeV=328.4 MeV

J.Ball et al., PRC4(1971)196

90Zr(p,t)88Zr

The enhancement factor ε has been used to compare the experimental intensities with those calculated on the basis of specific assumptions about the nuclear wave function involved. Disagreement between theory and experiment is indicated by deviations of ε from unity.

transition amplitude

isospin coefficient normalization factor (zero range approx.)

spectroscopic amplitude

enhancement factor

D.G.Fleming et al, PR165(1968)1153

for 1p and 2s1d shells

upper bound that can be expected in comparing (p,t) and (p,3He) reactions in the limit of pure S=0 transfer for (p,3He)

due to the additional S=1 spin transfer in (p,3He), the cross section ratio should be modified

scheme of levels from the harmonic pairing model

selection rules for (one step) two nucleon transfer reactions

In (3He,p) reactions p-n pairs may be transferred either with S=0,T=1 or with S=1,T=0. In (α,d) reactions only S=1,T=0 is possible.

GANIL in-beam gamma spectroscopy (fragmentation of 48Ca)

Date post:	06-Jan-2016
Category:	Documents
Upload:	minnie
View:	25 times
Download:	0 times

Heavy ion transfer reactions studied with PRISMA+CLARA

Documents