michael thoennessen, first ria summer school on exotic ...thoennes/personal/powerpoint/riasum… ·...

1

Michael Thoennessen,NSCL/MSU

First RIA Summer School on Exotic Beam Physics, August 12-17, 2002

Lecture 3: The Proton Dripline

Down and Up Along the Proton Dripline

Heavy One-Proton Emitter

Light One-Proton Emitter

Light Two-Proton Emitter

Heavy Two Proton Emitter

Proton Radioactivity

-60

-40

-20

0

20

40 Centrifugal (l=5)

Coulomb

NuclearRadius (fm)

V (M

eV)

20 40

Strong Influence on Angular Momentum

V (M

eV)

l=0

l=5

T1/2(l=0) = 3µsT1/2(l=5) = 81ms

E=1.25 MeV

Radius (fm)

-40

-20

0

20

20 40 8060

Lu15171 80

Heavy Proton Emitter

Long lifetimes due to Coulomb and angular momentum barrierProduce in fusion evaporation reactions or fragmentationSeparate and subsequently stop in a detector for identificationUse segmented silicon strip detectors for a delayed decay

1p Separation Energies (Odd p-numbers)

T. Radon et al., Pramana 53 (1999) 69

1p Separation Energies (Even p-numbers)

T. Radon et al., Pramana 53 (1999) 69

2




Structure and Deformed Emitters

C. J. Gross et al.113Cs

A. A. Sonzogni et al.131Eu, 141Ho, 145Tm

J. Uusitalo et al.155Ta

K. Rykaczewski et al.140Ho, 141Ho

T. N. Ginter et al.150Lu

K. S. Toth et al.151Lu

P. J. Woods and C. N. Davids, Annu. Rev. Nucl. Part. Sci. 47 (1997) 541

Q-Values and Branching Ratios

R. J. Irvine et al., Phys. Rev. C 55 (1997) R1621

C. N. Davids et al., Phys. Rev. C 55, (1997) 2255

161Re167Ir

Where is the Proton Dripline? “Short”-Lived Proton Emitters

C.R. Bingham et al.

100Sn

K. Sümmerer et al., Nucl. Phys. A616 (1997) 341c

rp - Process

5352515049

525150

5049484746

CoFe45

8079

8382

ZrNbMo

81

8483

M. F. Mohar et al., Phys. Rev. Lett. 66(1991) 1571

B. Blank et al., Phys. Rev. Lett. 77(1996) 2893

B. Blank, J. Phys. G 24 (1998) 1385

3




New Isotopes Along the Dripline

B. Blank, J. Phys. G 24 (1998) 1385B. Blank et al., Phys. Rev. Lett. 77 (1996) 2893

Prompt Decay from a Well-Deformed Band

γp

D. Rudolph et al., Phys. Rev. Lett. 80 (1998) 3018

First Proton Radioactivity

7/2-

3.04

0

19/2-

247 ms

0

3.19

(7/2-)

12

10

8

6

4

2

0

Ener

gy (M

eV)

0.840 0+

2+(19/2-)

β+

26Fe2753

26Fe2652

27Co2653

1.5%

Joseph Cerny and J. C. Hardy, Annu. Rev. Nucl. Part. Sci. 27 (1977) 333

β-Delayed Proton Emitters

S. Czajkowski et al., Nucl. Phys. A628 (1998) 537

Light Proton Emitter

(Very) short lifetimes due to small Coulomb and no or very small angular momentum barrier (l=0,1,2)Produce in transfer reactions or fragmentationIdentify by complete kinematic reconstruction in flight

151Lu and 12O

4




Definition of Radioactivity

Joseph Cerny and J. C. Hardy, Annu. Rev. Nucl. Part. Sci. 27 (1977) 333

“…should lead to lifetimes longer than 10-12 sec, a possible lower limit for the process to be called radioactivity.”

“…should lead to lifetimes longer than 10-12 sec, a possible lower limit for the process to be called radioactivity.”

Search for Di-Proton Emitters

Predicted by Goldansky in 1960Until recently (?) elusiveIn-Flight Decay (Short lifetimes)

Ground StateExcited States

Resonance ScatteringCoulomb ExcitationNeutron-Stripping

Implantation/Decay (Long lifetimes)Beta-Delayed Emitters Ground-State Emitters

Potential Two Proton Emitter Definitions

Di-Proton Decay Sequential Decay

12O

11N+p

10C+p+p

12O

10C+2p

10C+p+p

12O 10C+2p11N+p 12O 10C+2p11N+p

Simultaneous Decay

12O

10C+p+p

12O 10C+2p11N+p

Three Body Model

L. V. Grigorenko et al., Phys. Rev. Lett. 85 (2000) 22

Three-Body Decay Paths


5




Light Two-Proton Emitters Two-Proton Decay of 6Be

g.s.

1.67

0.59

-1.374He+2p

5Li+p6Be

(0+)(3/2-)

(2+)

D.F. Geesaman et al., Phys. Rev. C15 (1977) 1835

Transfer Reactions with Radioactive Beams

O13O13 O12

O12

Be9 Be10

TelescopeC10

p Light ChargedParticle Arrayp

Production and Identification of short-lived Nuclei

Decay Energy Spectrum of 12O

Γ = 575 keVEDecay = 1.77 MeV

Two-Proton Angular Distribution

Di-ProtonSequential

6




Decay Width

Sequential Decay

12O

11N+p

10C+p+p

12O 10C+2p11N+pHowever:Γcalc ≈ 10 keVΓmeasured = 575 keV

Elastic Resonance Scattering

L. Axelsson et al., Phys. Rev. C 54 (1996) R1511

Ground State of 11N

A. Azhari, et al. Phys. Rev. C57, 628 (1998)

J. M. Oliviera, et al. Phys. Rev. Lett. 84, 628 (2000)

K. Markenroth, et al. Phys. Rev. C62, 034308 (1998)

1.45 MeV1.63 MeV

1.27 MeV11N

Two Proton Decay of 12O

Old

New

??2.0 MeV1.8 MeV

1.8 MeV ~1.5 MeV

12O 11N+p 10C+2p

Di-Proton Decay of 16Ne?


New Shell Structure?

Z=8

N=8N=16 ?

N=20

??

7




Vanishing of the Proton Z=8 Shell ?

11N (-1.92MeV)

7B – 11N – 15F

5Li – 9B – 13N – 17F

Z=8

Vanishing of the Proton Z=8 Shell ?

11N (-1.27MeV)15F ??

Mass of 15F ??

11N 15F ??

Previous 15F Measurement

G. J. KeKelis et al., Phys. Rev. C 17, 1929 (1978)

Binding Energy of 15F : –1.47 MeV

Γ = 1 MeV

Theoretical Prediction

S. Grevy, O. Sorlin, and N. Vinh Mau, Phys. Rev. C56 (1997) 2885

Invariant Mass Measurements at GANIL

2%

87%

11%

Primary Beam: 24MgSecondary Beams:20Mg, 18Ne, 17FFragments Energies:35-43 MeV/nucleonStripping ReactionsDetectors:SPEG SpectrometerMUST array

8




15F → 14O + p

T. Zerguerras et al., to be published

Relative to KeKelis et al.

→ Binding Energy of 15F : Egs = –1.00 ± 0.08MeVΓ = 1.23 ± 0.22MeV

Mass of 15F !!

11N 15F !!

Two Proton Decay of 16Ne

Old

New

1.5 MeV1.4 MeV

1.4 MeV 1.0 MeV

??

16Ne 15F+p 14O+2p

15F

Two Proton Decay of 19Mg ??

Masses of 19Mg and 18Na are not knownStripping reactions:20Mg → 18Na → 17Ne + p20Mg → 19Mg → 17Ne + 2p

~1.8 MeV

~1.2 MeV ??

19Mg 18Na+p 17F+2p

Theoretical Predictions

First Measurement of the Mass of 18Na

No events observed for20Mg → 19Mg → 18Na + 2p

→ Binding Energy of 18Na : Egs = –0.411 ± 0.05 MeVΓ = 0.34 ± 0.09 MeV

Decay of 19Mg Sequential ??

~1.2 MeV

19Mg 18Na+p 17F+2p

0.41 MeV

Two-Proton Decay will most likely be sequential.... unless the mass of 19Mg is also underpredictedMeasure the mass of 19Mg

9




Intermediate (1p) Nuclei Two-Proton Decay of 14O*

2HeSequential

12C+2p

13N+p

14O

6.57

0

4.63

2.37

3.517.776.59

5.17

9.72

1/2+

3/2+

2+

0+

0+

C.R. Bain et al., Phys. Lett. B373 (1996) 35

Level and Decay Scheme of 17Ne γ-Decay of the First Excited State

M. J. Chromik et al., Phys. Rev. C55 (1997) 1676

Experimental Setup Decay Energy Spectrum of 17Ne

Counts

10




Experimental Setup

17Ne

Position sensitivedetectors

15O p

Target

40x40 Silicon strip detector:Low gain: ==> 15O positionHigh Gain: ==> proton position

2x2 Silicon quadrant detector:15O energy loss

2x2 Silicon quadrant detector:15O energy

48 element CsI detectorproton energy

40x40 Silicon strip detectorproton position energy

2x2 Silicon quadrant detector:proton energy loss

Breakup Reactions in the Detectors can be identified using the new Setup

15O,2p17Ne

15O,2p17Ne

Reaction in the Target

Breakup in the First Pin

∆E in Pin1 [MeV]

17Ne Penetrating the first Pin

Breakup Pos. [m]

Coulomb Excitation of 17Ne

Decay Energy [keV]

Num

ber o

f Cou

nts

M. Chromik et al, to be published

18Ne → 17Ne* → 15O + 2p

No evidence for 2p decay from the first excited state in 17Ne

Two-Proton Decay of 18Ne?

J. Gomez del Campo et al., Phys. Rev. Lett. 86 (2001) 43

One and Two Proton Decay

Γ1p= 50 keV

Γ2p= 21-57 eVJ. Gomez del Campo et al., Phys. Rev. Lett. 86 (2001) 43

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Correlated or Uncorrelated?

Relative Energy Opening Angle

J. Gomez del Campo et al., Phys. Rev. Lett. 86 (2001) 43

2p and 3p Decay of 31Ar

31Cl

31Ar18.55

12.34

β-decay

7.45

4.706.10

30S+p

29P+2p

28Si+3p

IAS

2p

3p

D. Bazin et al., Phys. Rev. C45 (1992) 69

I. Mukha et al., Nucl. Phys. A630 (1998) 394c

Two-Proton Radioactivity

W. E. Ormand, Phys. Rev. C53 (1996) 2145

W. E. Ormand, Phys. Rev. C55 (1997) 2407

B. A. Brown, Phys. Rev. C43 (1991) R1513

38Ti (0.4-2.3)x10-12 ms39Ti 0.4-2000 ms45Fe 10-5-10-1 ms48Ni 0.01-3660 ms63Se 0.3-5000 ms

Decay Width and Lifetime Predictions


45Fe: 2-Proton Decay at GSI

M. Pfützner et al., to be published

45Fe: 2-Proton Decay at GANIL

J. Giovinazzo et al., to be published

12




45Fe: Di-Proton or Sequential?

G. Audi and A.H. Wapstra, Nucl. Phys. A595 (1995) 409

Bridging the Waiting Points

H. Schatz et al., Phys. Rep. 294 (1998) 167

Two-proton emitters and the (2p,γ) rates

http://csep10.phys.utk.edu/astr162/lect/index.html

17Ne (γ ,2p) 15O

15O+2p 16F+p 17Ne

p

p

p

γ

15O(2p,γ)17Ne

15O+2p 16F+p 17Ne

p

p

p

γ

∆Q

-Qz Qz+1

Does the (2p,γ) compete with the (α,γ)

4

8

12

16

20

0.2 0.4 0.6 0.8 1-45

-40

-35

-30

-25

-20

-15

-10

-5

0.1 1

Total Reaction Rate

T (GK) T (GK)

Den

sity

[g/c

m3 ]

Lines of equal rates:

β = (α,γ)

β = (2p,γ)

(α,γ) = (2p,γ)

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20Ne(3He,6He)17Ne

V. Guimarães et al. Phys. Rev. C58 (1998) 116

New Level Scheme for 17Ne

V. Guimarães et al. Phys. Rev. C58 (1998) 116

5/2_

5/2_1/2+

1/2+

Modified Reactions Rates for 16F(p,γ)

Total Reaction Rate

-45

-40

-35

-30

-25

-20

-15

-10

-5

0.1 1

T (GK)

Does the (2p,γ) compete with the (α,γ) now?

4

8

12

16

20

0.2 0.4 0.6 0.8 1

T (GK)

Den

sity

[g/c

m3 ]

Lines of equal rates:

β = (2p,γ)

(α,γ) = (2p,γ)

β = (α,γ)

Use (γ,2p) to study (2p,γ)

Final nucleus following (2p,γ) is particle stableUse Coulomb dissociation (γ,2p) on stable nucleusPotential waiting point candidates:

15O(2p,γ)17Ne18Ne(2p,γ)20Mg38Ca(2p,γ)40Ti

64Ge(2p,γ)66Se68Se(2p,γ)70Kr72Kr(2p,γ)74Y

J. Görres, M. Wiescher, F.-K. Thielemann, Phys. Rev. C51, 392 (1995)

F. Käppeler, F.-K. Thielemann, and M. Wiescher,Ann. Rev. Nucl. Part. Sci. 48, 175 (1998)

68Se(2p,γ)70Kr

68Se+2p 69Br+p 70Kr

p

p

p

γ

High T (>2GK) : λtotal = λβ(Z) + f(T)*exp(∆Q)*λβ(Z+2)

∆Q

-Qz Qz+1

Low T (<2GK) : λtotal = λβ(Z) + g(T)*exp(-Qz)*<pγ>Ζ+1

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Reduction of Stellar Lifetime

H. Schatz et al., Phys. Rep. 294 (1998) 167

Energies and decay properties of the Z(waiting point +2) nucleus:

Coulomb excitation: (γ,γ) and (γ,2p)70Kr(γ,2p)68Se

Mass of the unstable Z(waiting point +1) nucleus:

Transfer reaction: 9Be(70Br,69Br)

68Se + p

What is needed?

Beam Intensities

70Kr(γ,2p)68Se 70Br

70Kr

68Se 9Be(70Br,69Br)

RIA: 8x107/s 70BrRIA: 4x104/s 70Kr

CC : 7x105/s 70BrCC : 3x102/s 70Kr

Conclusions

Still no conclusive evidence for di-proton decayLight nuclei:

“Phase space wins”: If it can decay sequential, it willGround-state di-proton decay very unlikelyLower ground-state energies measured for 11N, 15F and 18NaStill unresolved problem of large width in 12OMeasure 19Mg !!

Heavier nuclei:First evidence for two-proton decay in 45FeDetermine the proton correlationsMeasure the mass of 44MnDeformation, structure and mass measurements

michael thoennessen, first ria summer school on exotic ...thoennes/personal/powerpoint/riasum… ·...

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