Investigations of Halo Nuclei at the FRS

Abstract

The nuclei 8B and 19C were investigated in breakup reactions at relativistic energies. The fragment separator FRS at GSI was used as an energy-loss spectrometer to measure the longitudinal momentum distributions of the breakup fragments after one-nucleon removal.

Collaboration

T. Aumann, T. Baumann, L. Axelsson, U. Bergmann, M.J.G. Borge, D. Cortina-Gil, L. Fraile, H. Geissel, M. Hellström, M. Ivanov, N. Iwasa, R. Janik, B. Jonson, H. Lenske, K. Markenroth, G. Münzenberg, F. Nickel, T. Nilsson, A. Ozawa, A. Richter, K. Riisager, C. Scheidenberger, G. Schrieder, W. Schwab, H. Simon, B. Sitar, M.H. Smedberg, P. Strmen, K. Sümmerer, T. Suzuki, M. Winkler, and M.V. Zhukov

Nuclear halos are a well-established phenomenon for a few light nuclei close to the neutron drip-line, with 11Be and 11Li being the classical cases. These nuclei are well-described as two or three body systems, reflecting the halo structure in a rather simple way. But there are cases where the label halo is not so easily applied, among these are 8B, a nucleus at the proton drip-line with the small binding energy of 137 keV, and 19C, the last bound carbon isotope with odd neutron number. The question about the existence of a proton halo in 8B and the difficulties to describe the structure of 19C make these nuclei interesting cases to study in detail.


Longitudinal momentum distribution of 16,18C fragments after one-neutron removal from 17,19C, respectively. The breakup reactions occured in a 4.4 g/cm2 C target at about 900 MeV/u. The momentum distributions are transformed into the projectile frames and the deduced FWHM are 69±3 MeV/c for 18C and 141±6 MeV/c for the 16C distribution.

Together with 19C and 17C, we also measured the one-neutron removal from the stable nucleus 12C. Combining information on the one-neutron removal cross sections and the momentum distributions gives the nice picture displayed at the left, where the red, green, and cyan curves correspond to the longitudinal momentum distributions of 19C, 17C, and 12C, respectively.

Contact person

For further questions, please contact baumann@nscl.msu.edu.

Publications


Last updated: March 10th, 1999 created by Thomas Baumann