TEMPERATURE-DEPENDENCE OF QUANTAL AND THERMAL DAMPINGS OF THE HOT GIANT-DIPOLE RESONANCE

A systematic study of the damping of the giant dipole resonance (GDR) in Zr-90, Sn-120 and Pb-208 as a function of temperature T is performe d. The double-time Green function technique is employed to determine t he single-particle and GDR dampings. The single-particle energies, obt ained in the Woods-Saxon potential for these nuclei, are used in the c alculations. The results show that the coupling of collective vibratio n to the pp and hh excitations, which causes the thermal damping width , is responsible for the enlargement of the total width with increasin g temperature up to T approximate to 3 MeV and its saturation at highe r temperatures. The quantal width, which arises from the coupling of t he collective mode to the ph excitations decreases slowly with increas ing temperature. The effect of single-particle damping on the GDR widt h is small. The results are found in an overall agreement with the exp erimental data for the GDR width, obtained in the inelastic a scatteri ng and heavy-ion fusion reactions at excitation energies E less than or equal to 450 MeV. At high excitation energies (E > 400 MeV) a beha vior similar to the transition from zero to ordinary sounds is observe d. (C) 1998 Elsevier Science B.V.