Coulomb excitation of the 42Ca with AGATA Demonstrator

K. Hadyńska-Klęk1,2

P.J. Napiorkowski1, A. Maj3, F. Azaiez4, J.J. Valiente Dobon5

on behalf of the AGATA Collaboration

1) Heavy Ion Laboratory, University of Warsaw, Warsaw, Poland 2) Institute of Experimental Physics, University of Warsaw, Warsaw, Poland

3) H. Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences, Kraków, Poland4) Institute for Nuclear Physics, Orsay, France

5) INFN Laboratori Nazionali di Legnaro, Legnaro, Italy

42Ca 40Ca

Highly collective structure were found in the 40Ca (also in 36,38Ar)

B(E2; 4+ 2+ in SD) = 170 W.u (DSAM)

Deformation of the 2+ state in the superdeformed band: β2=0.59(9)

(E. Ideguchi et al.,

Phys. Rev. Lett. 87 2001)

40Ca vs 42Ca

B(E2) values in 42Ca suggest smaller deformation of the of the 0+(1837 keV) band than in the case of 40Ca

observation of GDR feeding of presumably deformed band in 42Ca from very deformed hot 46Ti (M.Kmiecik et al. Acta Phys. Pol. B36, 1169(2005))

moment of inertia very similar to that found for the SD-band in 40Ca

40Ca vs 42Ca

42Ca

42Ca COULEX @ LNL

beamtime: Feb.2010

beam: 42Ca, 170 MeV

target: 208Pb, 1 mg/cm2

DANTE: 3 MCP detectors

covered θ range 100°-144°

AGATA: 3 clusters

at 143.8 mm from the target

particle – γ coincidence mode: trigger rate 150÷250 Hz

Preliminary results

K. Hadyńska-Klęk et al., (Acta Phys. Pol B 42, 817 (2011))

Preliminary results

K. Hadyńska-Klęk et al., (Acta Phys. Pol B 42, 817 (2011))

Doppler Effect Correction

cos10 c

vEE

42Ca

42Ca

208Pb

Doppler Effect Correction

cos10 c

vEE

208Pb

42Ca

42Ca

208Pb

lines after Doppler correction – two MCP detectors at θ1=210o and θ2=150o

Tentative level scheme of 42Ca

K. Hadyńska-Klęk et al., (Acta Phys. Pol B 42, 817 (2011))

If 1- at 3885 keV…

• Excitation via E2(01+ → 21

+) and E3(21

+→ 1-) transitions

• Deexcitation via E1(1- → 02+ ) 2048 keV

• GOSIA calculations: B(E3; 21

+→ 1-) > 2.5*106 W.u.E2

E3

E1

If 1- at 3885 keV…

• Excitation via E2(01+ → 21

+) and E3(21

+→ 1-) transitions

• Deexcitation via E1(1- → 02+ ) 2048 keV

• GOSIA calculations: B(E3; 21

+→ 1-) > 2.5*106 W.u.E2

E3

E1

Postulated interpretationWe assume that the observed gamma line comes from a 2+ level placed at 2048 keV

The 22+ state can be populated directly via

E2(01+ → 22

+)

Deexcitation – through E2(22+ → 01

+) with 2048 keV

It was enough to reproduce the intensity of the

2048 keV gamma ray with B(E2; 22+ → 01

+) ~ 1 W.u

Observation of the 376 keV line supports this scenario

But...

No signs of this lines in the known level scheme and previous experiments

W.J. Kossler et al., Phys. Rev. 177, 1725 (1969)

Another unexpected effectIn multi-step Coulex each additional step leads to a weaker excitation →

we expected more counts in the 2424 keV line than in the 1729 keV transition

In the experiment, the 1729 keV line is stronger!

1729 keV = 4400 counts

2424 keV = 300 counts

It seems that the 42+ state is populated stronger

that the 22+ in the same band!

Excitation of the presumably SD band is smaller then it was expected or…

Deexcitation of 2424 keV state goes also through the 376 keV!

Motivation for the additional experiments

- coincidences analysis was performed but is not conclusive

As long as 376 and 2048 keV lines are not placed in the level scheme, the COULEX analysis results will require to make additional assumptions

Also proovement of the possible superdeformation will be less convincing

The aim of the additional experiments: investigation of the medium and low spin region in 42Ca

Experiment @ HIL Warsaw

Beam: 32S, 1 pnA, 76 MeV

Target: 12C, 4 mg/cm2

Reaction: 12C(32S,2p)42Ca

Cross section for 2p reaction channel:

110 mb (COMPA & PACE codes)

EAGLE-II array

The most important issues:

- possible new level at 2048 keV

- branching ratio determination of the decay lines from 2424 keV level

- ray angular correlation – to assign spin and parity of the new state(s)

Experiment @ HIL Warsaw

Beam: 32S, 1 pnA, 76 MeV

Target: 12C, 4 mg/cm2

Reaction: 12C(32S,2p)42Ca

Cross section for 2p reaction channel:

110 mb (COMPA & PACE codes)

EAGLE-II array

The most important issues:

- possible new level at 2048 keV

- branching ratio determination of the decay lines from 2424 keV level

- ray angular correlation – to assign spin and parity of the new state(s)

Any theories?

Any theories?

If yes, please contact me:

kasiah(at)slcj.uw.edu.pl

Special thanks toP.J. Napiorkowskia, A. Majb, F. Azaiezc, J.J. Valiente-Dobond, G. de Angelisd,

Anil Kumarb, D. Bazzaccoe, P. Bednarczykb, M. Bellatoe, G. Benzonif, L. Bertid, D. Bortolatod, B. Bruyneelg, F. Cameraf, M. Ciemałab, P. Cocconid, A. Colomboe, A. Corsif,F. Crespif, A. Czermakb, Ch. Drostei, B. Dulnyb, E. Farneae, B. Fornalb, S. Franchooc, A. Gadeah, A. Giazf, A. Gottardod,

X. Gravec, J. Gręboszb, E. Grodneri, M. Gulminid, H. Hessg, R. Isocratee, J.Iwanickia, G. Jaworskia,l, M. Kicińska-Habiori, M. Kmiecikb, N. Kondratyevj,

A. Korichim, W. Kortenn, J. Kownackia, M. Kowalczyka, M.Kisielińskia, G. Lehauto, S. Lenzie,k, S. Leonif, S. Lunardie,k, G. Marond, R. Menegazzoe, D.

Mengonip,e, E. Merchanr,s, W. Męczyńskib, C. Michelagnolie,k, J. Mierzejewskia, P. Molinie,k, D.R. Napolid, R. Nicolinif, M. Niikurac, M. Palacza, G. Rampazzoe, F. Recchiae,k, N. Redono, P. Reiterg, D. Rossod, E. Sahind, J.

Srebrnya, I. Stefanc, O. Stezowskio, J. Styczeńb, N. Toniolod, C.A. Ure, V. Vandonef, B. Wadswortht, A. Wiensg, K. Wrzosek-Lipskaa, M. Zielińskaa, M.

Zięblińskib

a) Heavy Ion Laboratory, University of Warsaw, Warsaw, Poland b) H. Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences, Kraków, Poland c) Institute of Nuclear Physics, Orsay, France d) INFN Laboratori Nazionali di Legnaro, Legnaro, Italy e) INFN Sezione di Padova, Padova, Italy f) Universita di Milano

and INFN sezione di Milano, Milano, Italy g) University of Cologne, Cologne, Germany h) IFIC, CSIC-University of Valencia, Valencia, Spain i) Institute of Experimental Physics, University of Warsaw, Warsaw, Poland j) Joint

Institute for Nuclear Research, Dubna, Russia k) Universita' di Padova, Padova, Italy l) Faculty of Physics, Warsaw University of Technology, Warsaw, Poland m) CSNSM Orsay, France n) CEA Saclay, France o) IPN

Lyon, France p) University of the West of Scotland, Paisley, UK r) TU Darmstadt, Germany s) GSI Darmstadt, Germany t) University of York, York, UK