Morsch et al. Reply:The author of the preceding Comment 1 questions the extraction of narrow giant-dipoleresonance (GDR) widths, a main point of our previous Letter. 2 His conclusion was derived from a different analysis using full statistical-model calculations, suggesting that the data were better described by large GDR widths.Meanwhile, we have performed full statistical-model calculations for all excitation energies and obtain results very similar to those in the Comment (by using the same parameters). However, a comparison with the experimental data (not done in the Comment) leads to the following conclusions:(1) The experimental data cannot be described adequately with either large or small GDR widths (see Fig. 1).(2) Divided spectra as shown in Ref. 2, Fig. 2, reveal a splitting of the GDR structure which can be explained only by narrow resonances. This must be true for any analysis, including those using statistical-model calculations.To prove this, the experimental data are divided by statistical-model calculations (see Fig. 2). Using the calculations with small GDR widths yields the spectrum in Fig. 2(a). This shows why the standard calculation fails to describe the data [point (l)]: A low-energy peak is observed which is well described by a Lorentzian at Eo = 7.5 MeV with T=4.2 MeV. In similar plots this peak is observed at all excitation energies and was also conjectured in other measurements. 3 Using statistical-model calculations including only this new peak yields Fig. 2(b) which shows a giant-resonance structure with splitting similar to Fig. 2 in Ref. 2. The description of this spectrum requires small resonance widths. In the original analysis presented in Ref. 1 the GDR widths were extracted by a fit with an empirical function, Tb = 300 MeV 162 MeV i ri L j iJLii 29 FIG. 1. /-ray spectrum, bremsstrahlung subtracted, for excitation energy E x -162 MeV, from Ref. 2. The solid and dashed lines indicate statistical-model calculations using small and large giant-resonance widths, respectively. The parameters were those discussed in the preceding Comment except for the solid line for which the energy-weighted sum-rule strength is reduced to 53%. J , L (a) EY = 162MeV **J*uiaiu nihil. Ill (b) FIG. 2. (a) y-ray spectrum divided by a model calculation, equivalent to the solid line in Fig. 1. The solid line is a Lorentzian fit to the structure at 7 MeV. (b) Same data divided by a calculation including only the new low-energy component; this shows the GDR structure. The solid and dashed lines represent calculations with narrow and broad GDR widths, respectively.inspired by the statistical model. The broad low-energy component found here is reflected in the old analysis in the value of the low-energy slope parameter T s , which is systematically larger than the value obtained for the standard statistical-model results (see Fig. 1).In summary, the y-ray spectra in Ref. 2 are not described by standard statistical-model calculations (discussed in the Comment), revealing a new low-energy dipole structure [ Fig...

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In an attempt to study isovector spin-flip excitations and to find a consistent picture of giant resonances in Pb, we analyzed giant resonance data from 172 MeV n scattering, 140 MeV 'He scattering, and 200 MeV proton scattering. Using spectroscopic information from n scattering, a good description of recent 'He scattering data is obtained. A detailed analysis of results from different probes reveals differences between complex particie and proton spectra which are interpreted as due to spin-flip contributions. The spin-flip strength is estimated in a microscopic p-h Inodel. At the scattering angles considered it gives resonant strength at -9 MeV dominated by 2 excitations and further gives an increasing continuum yield towards higher excitation energies. The cross sections of these spin-flip excitations in (p,p ) are comparable to giant resonance yields and have to be considered in order to obtain a description consistent with complex particle spectra. The continuum part of isoscalar excitations is rather different from that of isovector spin-flip excitations. These features are qualitatively understood from the nuclear matter response. Calculations using the semi-infinite nuclear slab model of Esbensen and Bertsch give an almost quantitative description of isoscalar and spin-isospin continuum.

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