Anomalous behaviour of 2+ excitations around 132Sn

S. Pietri, A. Jungclaus, R. Orlandi, D. Rudolph, A. Gadea et al.

Instituto de Estructura de la Materia – Consejo Superior de Investigaciones Científicas

GSI Darmstadt, IEM-CSIC Madrid, Lund University, IFIC-CSIC Valencia …

Anomalous behaviour of 2+ excitations around 132Sn

Cd E(2+) anomaly

Te B(E2)anomaly

?

What is the origin of these anomalies ?

The anomalous behaviour of E(2+) in the Cd isotopes

Cd E(2+) anomaly

Compare 48Cd and 52Te isotopic chains !

Beyond-mean-field calculations with particlenumber and angular momentum projection

T.R. Rodríguez, J.L. Egido, A. JungclausPhysics Letters B668 (2008) 410

Calculations reproducequalitatively the diffe-rent behaviour !

128Cd 132Te

Deformation as the main cause for the 2+

energy anomaly in the Cd isotopes towards N=82

peculiar coincidence of closed shellproton and neutron configurations

“blocking” of the oblate branch, where128Cd behaves as doubly-magic nucleus

prolate deformation of the 2+ state

2+T.R. Rodríguez, J.L. Egido, A. JungclausPhysics Letters B668 (2008) 410

with

Raman’s version of Grodzins’ formula

Habs’ factor

Te B(E2)anomaly

?

slight E(2+) and B(E2) asymmetries with respect to N=82

E(2+) for N=82+x < E(2+) for N=82-x B(E2) for N=82+x > B(E2) for N=82-x

except for the Te isotopes !

The anomalous behaviour of B(E2) in the Te isotopes

The anomalous behaviour of B(E2) in the Te isotopes

?

B(E2) = 0.103(15) e2b2

from low-energy Coulex

D. Radford et al., Phys. Rev. Lett. 88 (2002) 222501D. Radford et al., Nucl. Phys. A752 (2005) 264c

reanayzing the data yielded slightly larger value

D. Radford, private communication

B(E2) = 0.122(24) e2b2

from lifetime measurement (fast timing)

L.M. Fraile, H. Mach et al., Nucl. Phys. A805 (2008) 218

J. Terasaki et al., Phys. Rev. C66 (2002) 054313

D. Radford, A. Covello et al., Phys. Rev. Lett. 88 (2002) 222501

N. Shimizu, T. Otsuka et al., Phys. Rev. C 70 (2004) 054313

shell model B(E2) = 0.25 e2b2

QRPA B(E2) = 0.09 e2b2

shell model B(E2) = 0.15 e2b2

Remeasure B(E2) in 136Te withgood precision, measure B(E2)in 138Te for the first time !

beyond-mean-field study underway

The rate estimate

Primary beam: 238U @ 650 MeV/u intensity 109/sProduction target: 2.2 g/cm2 BeS4 rates: 1400 ions/s for 136Te and 130 ions/s for 138TeReaction target: 0.5 g/cm2 Au at S4Coulomb excitation cross section: 190 mb for 136Te (from known B(E2))-ray efficiency: =0.10 (606 resp. 443 keV for 136Te resp. 138Te)

Particle- coincidence rate: 3500 per day for 136Te 325 per day for 138Te

P.S.: normalization with known B(E2) in 136,138Xe contaminants

Rates allow for B(E2) measurements with good precision !