Nuclear dipole giant resonance

One sees from Figure 7.2 that the frequency of the nuclear dipole giant resonance decreases with increasing particle number. This is due to the short-range character of the nuclear forces which leads to a dispersion relation co = Vsq. The finite size sets a lower limit for the momentum as a /R oa which, in turn, predicts a trend... 

The particular SRPA versions for electronic Kohn-Sham and nuclear Skyrme functional were considered and examples of the calculations for the dipole plasmon in atomic clusters and giant resonances in atomic nuclei were presented. SRPA was compared with alternative methods, in particular with EOM-CC. It would be interesting to combine advantages of SRPA and couled-cluster approach in one powerful method. 

The integrated photonuclear cross section. The total integrated photo-nuclear cross section is an important quantity for it demonstrates that the giant resonance is caused, in the main, by absorption of electric dipole radiation. The total integrated cross section has been calculated by Levinger and Bethe. For electric dipole radiation, the cross section for absorption for a particular... 

Dipolresonanz s. Riesenresonanz, dipole resonance see giant resonance. direkte Dbergange, direct transitions 13, 71, 80. Dispersionstheorie der Kernreaktionen, dispersion theory of nuclear reactions 14. 

Nuclear science in particular obtains from laser-driven electron sources a brand new input to perform interesting measurements in the context of many laboratories equipped with ultrashort powerful lasers. The ultrashort duration of these particle bunches represent a further attractive feature for these kinds of studies. In the following, we will focus on nuclear reaction induced by gamma radiation produced by bremsstrahlung of laser-produced electrons in suitable radiator targets. This way is usually mentioned as photo-activation and is particularly efficient for photons of energy close to the Giant Dipole Resonance of many nuclei. 

In the 1950s, many basic nuclear properties and phenomena were qualitatively understood in terms of single-particle and/or collective degrees of freedom. A hot topic was the study of collective excitations of nuclei such as giant dipole resonance or shape vibrations, and the state-of-the-art method was the nuclear shell model plus random phase approximation (RPA). With improved experimental precision and theoretical ambitions in the 1960s, the nuclear many-body problem was born. The importance of the ground-state correlations for the transition amplitudes to excited states was recognized. 

Clusters also demonstrate the ubiquity and generality of the basic principles of physics the stability of metal clusters is governed by a shell closure closely related to that of nuclear physics. Indeed, the collective, giant dipole resonances in clusters and in nuclei obey the same laws over changes of fourteen decades in scale size. 

Left Spectra for the giant monopole and isoscalar dipole resonances obtained in (a,a ) measurements and right The extracted nuclear matter (nm) incompressibility constant /Cp, (Figure courtesy, P. H. Youngblood, Texas A M University)... 

The first depletion spectra obtained for neutral sodium clusters N = 2-40 were characterized by structureless broad features containing one or two bands. The results were interpreted in terms of collective resonances of valence electrons (plasmons) for all clusters larger than tetramers [2, 52-55]. The analogies between findings for metallic clusters and observations of giant dipole resonances in nuclei have attracted a large attention. Therefore the methods employed in nuclear physics, such as different versions of RPA in connection with the jellium model, have also been applied for studying the optical properties of small clusters. Another aspect was the onset of conductivity in metal-insulator transitions. 

In a next step, we compare nuclear and cluster response in the generic case of Coulomb excitation, as modeled by an initial shift of the electrons (respectively neutrons) with respect to ions (respectively protons). We first consider the nuclear giant dipole resonance. The lower panel of Figure 7.9 shows the power spectrum of the dipole along the z axis (symmetry axis) of after Coulomb excitation for several amplitudes with average excitation energies as indicated. The small-amplitude case represents the nuclear excitation spectrum in the linear regime as it is known from nuclear RPA calculations. We... 

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