Effective Widths and Effective Number of Phonons of Multiphonon Giant Resonances
نویسندگان
چکیده
We discuss the origin of the difference between the harmonic value of the width of the multiphonon giant resonances and the smaller observed value. Analytical expressions are derived for both the effective width and the average cross-section. The contribution of the Brink-Axel mechanism in resolving the discrepancy is pointed out. . ∗Supported in part by CNPq and FAPESP.
منابع مشابه
RELATIVISTIC HEAVY ION EXCITATION OF GIANT RESONANCESa
Giant resonances and giant resonances built on other giant resonances in nuclei are observed with very large cross sections in relativistic heavy ion collisions. A theoretical effort is underway to understand the reaction mechanism which leads to this process, as well as a better understanding of the microscopic properties of multiphonon states, e.g., their strength, energy centroids, widths an...
متن کاملTheory of multiphonon excitation in heavy-ion collisions.
We study the e ects of channel coupling in the excitation dynamics of giant resonances in relativistic heavy ions collisions. For this purpose, we use a semiclassical approximation to the Coupled-Channels problem and separate the Coulomb and the nuclear parts of the coupling into their main multipole components. In order to assess the importance of multi-step processes, we neglect the resonance...
متن کاملar X iv : n uc l - th / 9 50 70 27 v 1 1 4 Ju l 1 99 5 Theory of Multiphonon Excitation in Heavy - Ion Collisions
We study the effects of channel coupling in the excitation dynamics of giant resonances in relativistic heavy ions collisions. For this purpose, we use a semiclassical approximation to the Coupled-Channels problem and separate the Coulomb and the nuclear parts of the coupling into their main multipole components. In order to assess the importance of multi-step processes, we neglect the resonanc...
متن کاملMultiple giant resonances in nuclei: their excitation and decay
The excitation of multiphonon giant resonances with heavy ions is discussed. The conventional theory, based on the use of the virtual photon number method in conjunction with the harmonic model is presented and its shortcomings are discussed. The recently developed model that invoke the Brink-Axel mechanism as an important contribution to the cross-section is discussed and compared to the conve...
متن کاملth / 9 90 80 03 v 1 2 A ug 1 99 9 Microscopic Studies on Two - Phonon Giant Resonances
A new class of giant resonances in nuclei, namely double giant resonances, is discussed. They are giant resonances built on top of other giant resonances. Investigation on their properties, together with similar studies on low-lying two-phonon states, should give an answer on how far the harmonic picture of boson-type excitations holds in the finite fermion systems like atomic nuclei. The main ...
متن کامل