Coulomb breakup of neutron-rich $^{29,30}$Na isotopes near the island of
  inversion

Angelis, G. De; Aumann, T.; Beceiro-Novo, S.; Bleis, T. Le; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chakraborty, S.; Chartier, M.; Cortina-Gil, D.; Datta, Ushasi; Emling, H.; Ershova, O.; Fernandez, P. Diaz; Fraile, L. M.; Geissel, H.; Gonzalez-Diaz, D.; Johansson, H.; Jonson, B.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Langer, C.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Najafi, A.; Nilsson, T.; Nociforo, C.; Nowacki, F.; Panin, V.; Paschalis, S.; Plag, R.; Poves, A.; Rahaman, A .; Ray, I.; Reifarth, R.; Ricciardi, V.; Rigollet, C.; Rossi, D.; Scheidenberger, C.; Scheit, H.; Simon, H.; Taylor, J.; Togano, Y.; Typel, S.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.

research

Coulomb breakup of neutron-rich $^{29,30}$ Na isotopes near the island of inversion

Abstract

First results are reported on the ground state configurations of the neutron-rich

^{29,30}

Na isotopes, obtained via Coulomb dissociation (CD) measurements as a method of the direct probe. The invariant mass spectra of those nuclei have been obtained through measurement of the four-momentum of all decay products after Coulomb excitation on a

^{208}Pb

target at energies of 400-430 MeV/nucleon using FRS-ALADIN-LAND setup at GSI, Darmstadt. Integrated Coulomb-dissociation cross-sections (CD) of 89

(7)

mb and 167

(13)

mb up to excitation energy of 10 MeV for one neutron removal from

^{29}

Na and

^{30}

Na respectively, have been extracted. The major part of one neutron removal, CD cross-sections of those nuclei populate core, in its' ground state. A comparison with the direct breakup model, suggests the predominant occupation of the valence neutron in the ground state of

^{29}

Na

{(3/2^+)}

and

^{30}

Na

{(2^+)}

is the

d

orbital with small contribution in the

s

-orbital which are coupled with ground state of the core. The ground state configurations of these nuclei are as

^{28}

Na_{gs (1^+)\otimes\nu_{s,d} and

^{29}

Na

_{gs}(3/2^+)\otimes\nu_{ s,d}

, respectively. The ground state spin and parity of these nuclei, obtained from this experiment are in agreement with earlier reported values. The spectroscopic factors for the valence neutron occupying the

s

and

d

orbitals for these nuclei in the ground state have been extracted and reported for the first time. A comparison of the experimental findings with the shell model calculation using MCSM suggests a lower limit of around 4.3 MeV of the sd-pf shell gap in