FIZIKA B 12 (2003)  2, 117 - 134

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WEAK ABSORPTION AND RESONANCES IN LIGHT HEAVY-ION REACTIONS INDUCED BY THE NON-a-TYPE 14C NUCLEUS

SUZANA SZILNERa,b, FLORENT HAASb and ZORAN BASRAKa

aRuđer Bošković Institute, HR-10 002 Zagreb, Croatia
bInstitut de Recherches Subatomiques, CNRS-IN2P3/ULP, Strasbourg, France

Paper devoted to honour the memory of Professor Nikola Cindro

Received 28 January 2003; revised manuscript received 19 March 2003
Accepted 15 September 2003        Online 3 March 2004

The observation of resonant structures attributed to nuclear molecular configurations in a-type systems involving the 12C and 16O nuclei is a clear signature of a weak and surface-transparent absorption in these light heavy-ion reactions at energies around and up to well above the Coulomb barrier. Such a weak absorption, i.e. nuclear-surface transparency, is also predicted in reactions induced by the 14C nucleus owing to the very special structure of low-lying states of this non-a-type nucleus. The experimental search for resonant structures in the 14C +14C, 14C +12C and 14C +16O reactions undertaken by the Strasbourg-Zagreb collaboration is described and discussed in the context of weak-absorption phenomena. Strong and correlated resonances have been observed in the three systems studied and particularly in those decay channels which are sensitive to the largest partial waves in the entrance channel. As the incident energy increases, weak and surface-transparent absorption gives rise to refractive effects, i.e to the nuclear rainbow. Indeed, nuclear rainbows have been observed recently in the same a-type 12C +12C, 12C +16O and 16O +16O systems in which prominent nuclear molecular resonances have been reported at lower energies. It is predicted that such refractive effects should also be observed in the 14C-induced reactions at energies above ~5MeV per nucleon.

PACS numbers: 25.70.Bc, 25.70.Ef, 25.70.-z:
UDC 539.17

Keywords: heavy ions, 14C radioactive beam, 14C targets, molecular resonances, refractive effects, nuclear rainbow

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