LOI for the AGATA-PRESPEC campaign, GSI

Spectroscopy and B(E2) measurements in neutron rich Mo nuclei:Search for shape transitions near the astrophysical r-process path

T. Bäck, B. Cederwall, F. Ghazi Moradi, A. Atac, J. Blomqvist, A. Dewald, E. Ganiouglu, J. Gerl, M. Gorska, E. Ideguchi, A. Johnson A. Khaplanov, P. Magierski,O. Möller,J. Nyberg, S. Pietri, M.

Sandzelius, P.-A. Söderström, H.-J. Wollersheim, R. Wyss et al.(author list to be completed)

Mean field calculatations of quadrupole deformations (e.g. Möller et al.) predict a prolate-oblate shape transformation in neutron rich Mo isotopes.

Good testing ground for nuclear models

Experimental approach:

B(E2) via gamma-particle coincidences(+ RDDS)

Astrophysical r-process path

http://www.cenbg.in2p3.fr/heberge/desir/IMG/gif/tas_1.gif

112Mo

Predicted shape transitions in heavy Mo isotopes (TRS)

108Mo112Mo

F. R. XU, P. M. WALKER, AND R. WYSS PHYSICAL REVIEW C 65 021303~R

E(2+) and B(E2) systematics

Exp. Data om heavy Mo isotopes up to 110Mo from spontaneous fission of 248Cm and 252Cf. But yield decreases “exponentially” as a

function of neutron number.

W. Urban et al., EPJ A20 381 (2004)Ding et al., Chinese Phys. Lett. 24 1517 (2007)

Coulex of gamma-vibrational states

Rate estimation for n-rich Mo isotopesproduced in fast fission of 238U

Nuclide RIB rate at S4 cross section N(particle-gamma)pps(a) / pps (b) [mb] per day

Mo-108 217(a) / 3.8(b) 675 (Coulex) 18000(a) / 315 (b)

Mo-110 49(a) / 36(b) 675 (Coulex) 4000(a) / 3000(b)

Mo-112 0.8(a) / 2.33(b) 675 (Coulex) 66(a) / 193(b)

Production and transmission calculation using LISE++ Gamma efficiency: 15% (very conservative at 200 keV)Primary 238U Beam: 4·109 particles per second0.55 g/cm2 Be primary target0.8 g/cm2 Pb secondary targetKE of Mo ions 100 – 130 MeV/u at sec tgt“a” and “b” indicate two different FRS settings optimized for108Mo and 112Mo, respectively.