Freiburg 1999 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 40: Theorie V

HK 40.6: Talk

Wednesday, March 24, 1999, 16:45–17:00, A

Chaotic scattering on surfaces and collisional damping of collective modes — •U. Fuhrmann¹, M. Vogt¹, K. Morawetz¹, P. Lipavskyý², and V. Spička² — ¹Fachbereich Physik, Universität Rostock, Universitätsplatz 3, D-18051 Rostock — ²Institute of Physics, Academy of Sciences, Cukrovarnická 10, 16200 Praha 6, Czech Republic

The damping of hot giant dipole resonances is investigated. The contribution of surface scattering is compared with the contribution from the interparticle collisions. A unified response function is derived which includes surface damping as well as collisional damping. The surface damping enters the response via the Lyapunov exponent and the collisional damping via the relaxation time. The former one is calculated for different shape deformations of quadrupole and octupole type. The surface as well as the collisional contribution each reproduce the experimental value, therefore we propose a proper weighting between both contributions related to their relative occurrence due to collision frequency between particles and of particles with the surface. Experimental data can be reproduced. We find that for low and high temperatures the collisional contribution dominates whereas the surface damping is dominant around temperatures of a third of the centroid energy.

[1] U. Fuhrmann, K. Morawetz, R. Walke, Phys. Rev. C 58 (1995), 1473

[2] K. Morawetz, U. Fuhrmann, R. Walke, M. DiToro, Phys. Rev. C 57 (1998), R2813.

[3] K. Morawetz, U. Fuhrmann, R. Walke Nucl. Phys. A (1998), in press

[4] K. Morawetz, U. Fuhrmann, P. Lipavskyý, V. Spička Phys. Rev. C (1998), sub.