1. Reorientation-effect measurement of the first 2 State in C: Confirmation of oblate deformation
- Author
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Kumar Raju, M., Orce, J.N., Navrátil, P., Ball, G.C., Drake, T.E., Triambak, S., Hackman, G., Pearson, C.J., Abrahams, K.J., Akakpo, E.H., Al Falou, H., Churchman, R., Cross, D.S., Djongolov, M.K., Erasmus, N., Finlay, P., Garnsworthy, A.B., Garrett, P.E., Jenkins, D.G., Kshetri, R., Leach, K.G., Masango, S., Mavela, D.L., Mehl, C.V., Mokgolobotho, M.J., Ngwetsheni, C., O'Neill, G.G., Rand, E.T., Sjue, S.K.L., Sumithrarachchi, C.S., Svensson, C.E., Tardiff, E.R., Williams, S.J., and Wong, J.
- Abstract
A Coulomb-excitation reorientation-effect measurement using the TIGRESS γ−ray spectrometer at the TRIUMF/ISAC II facility has permitted the determination of the 〈21+‖E2ˆ‖21+〉 diagonal matrix element in $^{12}$C from particle−γ coincidence data and state-of-the-art no-core shell model calculations of the nuclear polarizability. The nuclear polarizability for the ground and first-excited (21+) states in $^{12}$C have been calculated using chiral NN N$^{4}$LO500 and NN+3NF350 interactions, which show convergence and agreement with photo-absorption cross-section data. Predictions show a change in the nuclear polarizability with a substantial increase between the ground state and first excited 21+ state at 4.439 MeV. The polarizability of the 21+ state is introduced into the current and previous Coulomb-excitation reorientation-effect analyses of $^{12}$C. Spectroscopic quadrupole moments of QS(21+)=+0.053(44) eb and QS(21+)=+0.08(3) eb are determined, respectively, yielding a weighted average of QS(21+)=+0.071(25) eb, in agreement with recent ab initio calculations. The present measurement confirms that the 21+ state of $^{12}$C is oblate and emphasizes the important role played by the nuclear polarizability in Coulomb-excitation studies of light nuclei.
- Published
- 2017