Ядерна фізика та енергетика Nuclear Physics and Atomic Energy   ISSN: 1818-331X (Print), 2074-0565 (Online)   Publisher: Institute for Nuclear Research of the National Academy of Sciences of Ukraine   Languages: Ukrainian, English   Periodicity: 4 times per year   Open access peer reviewed journal

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T. I. Mikhailova¹, A. G. Artyukh¹, M. Colonna², M. Di Toro², B. Erdemchimeg^1,3, G. Kaminski^1,4, I. N. Mikhailov¹, Yu. M. Sereda^1,5, H. H. Wolter<sup>6

1</sup>Joint Institute for Nuclear Research, Dubna, Moscow region, Russia
²Laboratori Nazionali del Sud, Istituto Nazionale di Fisica Nucleare, Catania, Italy
³Mongolian National University, Nuclear Research Center, Ulaanbaatar, Mongolia
⁴Institute of Nuclear Physics PAN, Krakow, Poland
⁵Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine
⁶Faculty of Physics, University of Munich, Garching, Germany

Abstract: Heavy ion collisions in the Fermi energy regime may simultaneously show features of direct and dissipative processes. To investigate this behavior in detail, we study isotope and velocity distributions of projectile-like fragments in the reactions ¹⁸O (35 MeV/A) + ⁹Be(¹⁸¹Ta) at forward angles. We decompose the experimental velocity distributions empirically into two contributions: a direct, 'break-up' component centered at beam velocity and a dissipative component at lower velocities leading to a tail of the velocity distributions. The direct component is interpreted in the Goldhaber model, and the widths of the velocity distributions are extracted. The dissipative component is then successfully described by transport calculations. The ratio of the yields of the direct and the dissipative contributions can be understood from the behavior of the deflection functions. The isotope distributions of the dissipative component agree qualitatively with the data, but the modification due to secondary de-excitation needs to be considered. We conclude that such reactions are of interest to study the equilibration mechanism in heavy ion collisions.

1. Veselsky M. et al. Heavy residues with A < 90 from the asymmetric reaction of 20 AMeV ¹²⁴Sn + ²⁷Al as a sensitive probe of the onset of multifragmentaion. Nucl. Phys. A 724 (2003) 431. https://doi.org/10.1016/S0375-9474(03)01571-9

2. Kaminski G. et al. Analysis of production of forward-angle fragments in the ²²Ne(40 MeV) + ⁹Be reaction. Nucl. Phys. and Atom. Energy 9 (2008) 39. https://jnpae.kinr.kyiv.ua/25(3)/Articles_PDF/jnpae-2008-3(25)-0039-Kaminski.pdf

3. Gelbke C. K. et al. Influence of intrinsic nucleon motion on energy spectra and angular distributions for ¹⁶O-induced reactions at 20 MeV/A. Phys. Lett. B 70 (1977) 415. https://doi.org/10.1016/0370-2693(77)90402-6

4. Lahmer W. et al. Transfer and fragmentation reactions of ¹⁴N at 60 MeV/u. Z. Phys. A 337 (1990) 425; https://doi.org/10.1007/BF01294980

Bacri Ch. O. Measurements in the beam direction of the ⁴⁰Ar projectile fragmentation at 44 MeV/A. Nuc. Phys. A 555 (1993) 477. https://doi.org/10.1016/0375-9474(93)90297-B

5. Borrel V. et al. Peripheral Ar induced reactions at 44 MeV/u - similarities and deviations with respect to a high energy fragmentation process. Z. Phys. A 73 (1983) 191. https://doi.org/10.1007/BF01879877

6. Notani M. et al. Projectile fragmentation reactions and production of nuclei near the neutron drip line. Phys. Rev. C 76 (2007) 044605. https://doi.org/10.1103/PhysRevC.76.044605

7. Goldhaber A. S. Statistical model of fragmentation processes. Phys. Lett. B 53 (1974) 306. https://doi.org/10.1016/0370-2693(74)90388-8

8. Schröder U., Huizinga J. R. Damped nuclear reactions. Treatise on Heavy-Ion Science. Vol. 2. Ed. by A. Bromley (New York: Plenum, 1984) p. 113.

9. Mikhailova T. et al. Investigation of dissipative collisions with transport models. Rom. Journ. Phys. 52 (2007) 875.

10. Mikhailova T. et al. Description of deep inelastic transfer reactions at the Fermi energy within transport models. Bull. of the Russian Academy of Sciences. Phys. 72 (2008) 339. https://doi.org/10.3103/S1062873808030155

11. Artukh A. G. et al. QMD approach in the description of the ¹⁸O + ⁹Be and ¹⁸O + ¹⁸¹Ta reactions at E_proj = 35 AMeV. Acta Physica Polonica B 37 (2006) 1875.

12. Rivet M. F. et al. Dynamical aspects of violent collisions in Ar + Ag reactions at E/A = 27 MeV. Phys. Lett. B 215 (1988) 55. https://doi.org/10.1016/0370-2693(88)91069-6

13. Artukh A. G. et al. Some regularities in the beam-direct production of isotopes with 2⩽Z⩽11 induced in reactions of ¹⁸O (35 A MeV) with Be and Ta. Nucl. Phys. A 701 (2002) 96. https://doi.org/10.1016/S0375-9474(01)01554-8

14. Bertsch G. F., Das Gupta S. A guide to microscopic models for intermediate energy heavy ion collisions. Phys. Rep. 160 (1988) 189. https://doi.org/10.1016/0370-1573(88)90170-6