P.R.S. Gomesa,*, J. Lubiana, b, I. Padrona, R.M. Anjosa, D.R. Otomar a, L.C. Chamonc, and E. Crema c
a Instituto de Física, Universidade Federal Fluminense, Av. Litoranea s/n, Gragoata, Niterói, R.J., 24210–340, Brazil, *e–mail: paulogom@if.uff.br
b Center of Applied Studies to Nuclear Development, Havana, P.O. Box 6122, Cuba.
c Departamento de Física Nuclear, Universidade de São Paulo, Caixa Postal 66318, 05315–970, São Paulo, S.P., Brazil.
Recibido el 3 de enero de 2006
Aceptado el 30 de marzo de 2006
Abstract
We discuss the influence of the break–up process of stable weakly bound nuclei on the fusion cross section and on the elastic scattering at near barrier energies. The complete fusion for heavy targets is found to be suppressed at energies above the barrier, whereas this effect is negligible for light targets. The total fusion cross sections are not affected by the break–up process. The non capture break–up is the dominant process at sub–barrier energies, with significant cross sections also at energies close and above the Coulomb barrier. We also show that the break–up process is responsible for the vanishing of the usual threshold anomaly of the optical potential and give rise to a new type of anomaly, named break–up threshold anomaly (BTA).
Keywords: Break–up process; fusion cross sections; break–up threshold anomaly.
Resumen
Se discute la influencia del proceso de ruptura de núcleos estables débilmente enlazados en la sección eficaz de fusión y en la dispersión elástica a energías próximas a la de la barrera de Coulomb. La sección eficaz de fusión completa para blancos pesados es suprimida para energías superiores a la de la barrera de Coulomb, mientras que este efecto es despreciable para blancos ligeros. La sección eficaz de fusión total no es afectada por el proceso de ruptura. El proceso de ruptura sin captura de residuos es el proceso dominate a energías inferiores a la de la barrera, con secciones eficaces considerables también para energías del orden de la barrera de Coulomb y supeiores. Mostramos además, que el proceso de ruptura es el responsable por la ausencia de la anomalía de umbral usual del potencial óptico y conlleva a un nuevo tipo de anomalía, llamado anomalía de umbral de ruptura (BTA).
Descriptores: Proceso de ruptura; sección eficaz de fusión; anomalía de umbral de ruptura.
PACS: 25.60.Gc; 25.70 Jj; 25.70 Mn; 25.60 Dz
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Acknowledgements
The authors would like to thank the CNPq, CAPES, FAPERJ and FAPESP for their financial support.
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