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HK: Physik der Hadronen und Kerne
HK 31: Postersitzung / Theorie
HK 31.11: Poster
Wednesday, March 24, 1999, 10:15–12:00, Foyer
The doorway concept at high excitation energy — •E. Persson1,2 and I. Rotter1,2 — 1Technische Universität, Institut für Theoretische Physik, 01062 Dresden — 2Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden
Recently, the giant dipole resonance observables have been investigated experimentally in hot rotating nuclei [1]. The results showed, among others, that collisional damping at the temperature T≈ 2 MeV is practically the same as at zero temperature. This result is a challenge for the theory. It is necessary to prove the doorway concept under the conditions of extremely high excitation energy. In doing this, one has to consider the quantum system as being open, i.e. one should take into account that the nuclear states are embedded in the continuum of decay channels.
In the present paper [2], the spreading of transition strength is studied in the doorway picture by taking the coupling to the continuum explicitly into account. The internal (configurational) coupling mixes the doorway state with the background states and is responsible for all the states actually having a decay width. Therefore, external mixing of the states via the continuum is induced. If it is large, resonance trapping appears and the states will be demixed. Thus, the residual interaction is effectively reduced. As a consequence, the spreading of transition strength can be small also at high excitation energy. The relation to the golden rule is discussed.
[1] A. Bracco et. al., Phys. Rev. Lett. 74, 3748 (1995); Nuovo Cimento 1998 (Proceedings SNEC98); M. Mattiuzzi et al., Phys. Lett. B 364, 13 (1995); Nucl. Phys. A 612, 262 (1997)
[2] E. Persson and I. Rotter, Phys. Rev. C (in press)