Spectroscopy of exotic nuclei Lecture 4 Superheavy Elements (continued) Shape coexistence R. Krücken - XVth UK Postgraduate School in Nuclear Physics –

Spectroscopy of exotic nuclei

Lecture 4

Superheavy Elements (continued)

Shape coexistence

R. Krücken - XVth UK Postgraduate School in Nuclear Physics – Lecture 4

„Cold“ Fusion

• medium heavy projectile on doubly magic target 208Pb• low excitation energy of Compund nucleus• Evaporation of single neutron

Low excitation energy results from shell closure of target nucleus

„Cold“ Fusion

2R. Krücken - XVth UK Postgraduate School in Nuclear Physics –

Lecture 4

SHIP Experiment at GSI Darmstadt

Electric dipole

Magnetic dipoleBeam stop

Magneticquadrupole

Targetwheel

Position sensitivefocal plane

detector

Time of flightdetectorsMaximal: 0.3 particle mA = 2.1012 pps


Lecture 4

eq

mvEρ

eq

mvBρ

2

Decay of 265Hs (Z=108)

Rf253

sf48 s

Rf254

sf

Rf256

sf,a

Rf257

a ,ec

4.7s

a,ec

Rf258

sf13 ms

Rf259

a,sf3.1 s

Rf260

sf21 ms

Rf261

a

78 sRf262

sf

47ms1.4sRf255

a,sf0.8s

a,sf1.4s 2.1s

sf

Db257

a,sf1.3 s

Db258

a,ec4.4 s

Db260

a,ec/sf?1.5 s

Db261

a,sf1.8 s

Db262

a ,ec/sf?34 s

Db263

a,sf27 s

Sg265

a,sf?7.4 s

Sg266

a,sf?21 s1.4s

Sg263

a0.3s

a ,sf?0.9s

Sg261

a ,ec0.23 s

Sg260

a ,sf3.6 ms

Sg259

a0.48 s

Sg258

sf2.9 ms

Bh261

a11.8 ms

Bh264

a440 ms

Bh262

a102ms

a8ms

Db256

a,sf2.6 s

Db255

a ,sf1.6 s

Bh260

a?

Hs263

a?

Hs264

a,sf0.45 ms

Hs265

a

0.8ms

a

1.7ms

a

Hs267

59 ms

Hs269

a 9.3 s

RfRuther-fordium

DbDubnium

SgSeaborgium

BhBohrium

HsHassium

105

106

107

108

150 152 154 156 158

160

N

a-decay Spont.anneous fission EC-decay

Z

Bh266

a» 1s

Bh267

a» 17 s

Hs266

2.3 msa a

Sg262

sf6.9 ms

23 s 6.1 s

• Successive decay must happen at same position

• a-energies must coincide with known decay energies

a-Energies


Lecture 4

Gas-filled separator

• Magnetic field region filled with ~ 1 Torr He Gas

• Heavy ion leaves target with charge distribution

• Scattering of ion with gas (velocity of bound electrons)

charge exchange reactions narrow charge distribution around average charge state

Þ higher acceptance compared to vacuum system since only few charge states are accepted in vacuum system

• in first order magnetic rigidity B is independent of velocity since average charge state depends on velocity

large acceptance

BUT - Low mass resolution- Low background reduction

B = 0.0227 A v/v0 q-

1

q = v/v0 Z1/3


Lecture 4

Dubna gas-filled separator


Lecture 4

Hot Fusion

• light projectile onto actinide target è neutron rich isotope• high excitation energy of compound nucleus

Evaporation of several neutrons

Probability for „survival“ of compound nucleus: each evaporation of a neutron is in competition with fission

FN

NNP

xi

iNXN PP

...1

)(

Hot Fusion


Lecture 4

Nuclear chart of transactinides in 2008

Rf253

sf48 s

Rf254

sf

Rf256

sf,a

Rf257

a,ec4.7sa,ec

Rf258

sf13 ms

Rf259

a,sf3.1 s

Rf260

sf21 ms

Rf261

a78 s

Rf262

sf47ms1.4s

Rf255

a,sf0.8s

a,sf1.4s 2.1s

sf

Db257

a,sf1.3 s

Db258

a,ec4.4 s

Db260

a,ec/sf?1.5 s

Db261

a,sf1.8 s

Db262

a,ec/sf?34 s

Db263

a,sf27 s

Sg265

a,sf?7.4 s

Sg266

a,sf?21 s1.4s

Sg263

a0.3s

a ,sf?0.9s

Sg261

a,ec0.23 s

Sg260

a,sf3.6 ms

Sg259

a0.48 s

Sg258

sf2.9 ms

Bh261

a11.8 ms

Bh264

a440 ms

Bh262

a102ms

a8ms

Db256

a,sf2.6 s

Db255

a,sf1.6 s

Bh260

a?

Hs263

a?

Hs264

a,sf0.45 ms

Hs265

a0.8ms

a1.7ms

a

Hs26759 ms

Hs269

a 9.3 s

Mt266

a1.7 ms

Mt268

a70 ms

110267

a?

110271

a1.1ms

a56 ms

110273

a76 ms

a118ms

269

a170 ms

110

272

a1.5 ms

111

112277

a194ms

a277ms

RfRuther-fordium

DbDubnium

SgSeaborgium

BhBohrium

HsHassium

MtMeitnerium

112

105

106

107

110

109

108

112

111

150 152 154 156 158

160

162

164

NA-decay Spont. fission EC-decay

Hs277

sf»10 min

281

a»1 min

285

a»10 min

112

110

289

a»20 s

114287

a»5 s

114

283

sf 3 min

112

114114

116

166 168

170 172

Z

116

174

284

a»10 s

112

a»2 s

114288

280

sf »7 s

110

Bh266

a» 1s

Bh267

a» 17 s

292

a» 33 ms

116

Hs2662.3 msa a

Sg262

sf6.9 ms

110270

a0.1ms

a6 ms

23 s 6.1 s

Darmstadtium (Ds)

“Problems” of Dubna results:

- decays often end in unknown isotopes

- short decay chains

- long correlation times283113 284113282113

286114

288115287115

290116 291116 293116

New elements/isotopes since 2001

294118118

115

113 176

Roentgenium (Rg)282112

278113

274Rg 278Rg 279Rg 280Rg

270Mt 276Mt275Mt274Mt

270Hs 271Hs275Hs

270Bh 271Bh 272Bh

267Sg 271Sg

266Db 268Db267Db259Db

263Rf 267Rf

hotfusion

279Ds


Lecture 4

Copernicium (Cp)Suggestion:

Cross-sections


9

D. Ackermann

48Ca + 238U → 286112* - Summary


10

D. Ackermann

Independent confirmation of Dubna result !!

Spectroscopy of 254No

48Ca + 208Pb

Cross section: ~500 nb

(large due to doubly magic projectile and target nuclei)


Lecture 4

Gamma spectroscopy of 254No at RITU


Lecture 4

JUROGAM

Identification of 254No through a-decay

26 MeV 40 MeV

15 MeV 55 MeV

Implantation

Alpha decay


Lecture 4

Rotational spectra in 254No

Gamma rays of nuclei at target position!!!

In coincidence with detected recoils

In coincidence with alpha decay transitions of 254No decay chain


Lecture 4

SACRED


Lecture 4

Conversion electrons guided by Solenoid magnet to segmented Si Detector

Confirmation of deformation of 254No


Lecture 4

Chemistry of SHE

Situation as of one century ago


Lecture 4

Periodic Table of the Elements

A. Türler, RCM, TUM

Does Hs behave like

Os?


Lecture 4

Recoilchamber

269,270Hs

26Mg-beam

248Cm target

He/O2He/O2

2x 36PIN-diodes

PFA-tefloncapillary

thermostat

(-20°C)

N2(liq.) cooling

oven (600°C)

SiO2-column(i.D. 4 mm)

-170 °C

-20 °C

0 40 cm

HsO4 deposition

rotatingVacuum window

In-Situ Volatilization and On-line detection (IVO)


Lecture 4

Shape coexistence


21

Predictions of superheavy nuclei

withshell corrections

withoutshell correction

Strutinsky, Nuclear Physics A951967

2nd minium at large deformation(superdeformation / shape coexistence)


Lecture 4

Existence of superheavy nuclei

Shape coexistence in 152Dy

SD states become yrast at I » 60ħ

ProlateND Minimum

SD Minimum

OblateND Minimum


Lecture 4

High spin spectroscopy

Population of nuclei at high angular momentumin Fusion-Evaporation-Reaction EUROBALL


Lecture 4

Shape coexistence in 152Dy

linking transitions unknown

.)()2( constIEIEE


Lecture 4

Superdeformation

SuperdeformationNuclei with long to shortAxis ratio of » 2:1

Around 250superdeformed bandshave been observed

Low-spin superdeformed states are at high energies with respect to ground state


Lecture 4

Shape isomerism around 74Kr


27

M. Bender et al., PRC 74, 024312 (2006) Adopted from A. Görgen

Electron conversion spectroscopy


28

Isotope shifts in Hg

weaklyoblate deformed

stronglyprolate deformed

b = -0.1

b = -0.17

b = 0.25-0.28

...

10/,2,

6,,,,

AA

ElektronenAA

Feld

AAIS

AAFeld

AAMasse

AAIS

rF

Isotope shift (IS) of atomic transitions

Mean square charge radius <r2>

collinear laser spekctroscopy


Lecture 4

Shape coexistence in 186Pb

Protonen-Konfigurationen

0p-0h 4p-4h2p-2hA. Andreyev et al., Nature 405, 430 (2000)


Lecture 4

M(186Pb) ~ 174 GeV/c2

Subtle balance of nuclear forces leads to competition on the 1 MeV level (6∙10-6)

SHIP velocity filter at GSI


Lecture 4

Shape coexistence in 186Pb – a-Spectra

“Penetration”-factor P depends on shape!

PT

Ih

100

)2ln(

2/1

2 Reduced a-width d2:Measure for creation ofa-particle in the nucleus Û p-h configuration

prolateoblate

spherical

Large overlap: (only protons)|Po;2p-0h> ® |Pb;0p-0h>|Po;4p-2h> ® |Pb;2p-2h>

analogy: spectroscopic factors

PoAPb


Lecture 4

A. Andreyev et al., Nature 405, 430 (2000)

Shape coexistence in the light Hg nuclei


Lecture 4

Plunger + Ritu@Jyväskylä

He at 1-2 mbar

C- foil

QDQ

Q

target

RITU separator~ 30% recoil eff. beam

JUROGAM Ge-array~ 4% efficiency


Lecture 4

T. Grahn et al., PR L97 (2006) 062501 T. Grahn et al., PRC80 (2009) 014324

Lifetime measurement in 180Hg


35

T. Grahn et al., PRC 80, 014324 (2009)

Coulex of 184,186,188Hg at REX-ISOLDE

184Hg

Online spectrumTarget: 120Sn

P. Butler et al.

535 keV22

+ 01+

287 keV41

+ 21+

367 keV21

+ 01+

01+

21+

22+

41+

02+

Aim:- Measure E2 transition and diagonal matrix elements deformations


Lecture 4

Superheavy elementsNuclear Structure at the extremes

New shell gaps through residual interaction

Shell quenching bydiffuse surface

Halos

Soft collective modes

Neutron Skins

Shape coexistence

Cluster

Isospin competitionand symmetry


Lecture 4

Thank you for your attention!!


38

Spectroscopy of exotic nuclei Lecture 4 Superheavy Elements (continued) Shape coexistence R. Krücken - XVth UK Postgraduate School in Nuclear Physics –

Documents

s sf db

s successive decay

nuclear physics lecture

anneous fission ecdecay

charge states

magic target

known decay energies

fission hot fusion