Microscopic Calculations of the Background below Giant Resonances
نویسندگان
چکیده
Using a microscopic 1 p a r t i c l e 1 hole doorway model fo r nuclear exci ted states we show that the continuous forward angle energy spectra of medium energy (p .n) react ions are mainly a resu l t of d i rec t one-step processes. The model is appl ied to the reactions Ca(p,n) at 160 MeV and to 9 0 Zr (p ,n ) at 200 MeV incident energy. In case of 9 0 Zr (p ,n ) we f i nd that a large f r ac t i on of Gamow-Teller strength i s located in the high exc i ta t i on energy region 15<E <50 MeV. There are ind icat ions that the t r a n s i t i o n strength of the s p i n f l i p giant dipole (AL=1, A S = 1 , A T = 1 ) resonance is quenched by roughly 50 %.
منابع مشابه
th / 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 کاملBoson expansion methods applied to a two-level model in the study of multiple giant resonances
We apply boson expansion methods to an extended Lipkin-Meshkov-Glick model including anharmonicities in analogy with previous microscopic calculations. We study the effects of different approximations present in these calculations, among which the truncation of the hamiltonian and of the space, in connection with the study of the properties of two-phonon and three-phonon states. By comparing th...
متن کاملRELATIVISTIC 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 کاملMicroscopic calculation of double-dipole excitations
In the last decade experimental and theoretical research has led to the discovery of double giant resonances—a giant resonance built on top of another giant resonance. The double-dipole resonance was first identified in a pion charge exchange reaction @1# and was predicted earlier @2#. Later the double dipole was detected in Coulomb excitation in heavyion reactions @3–5#. Properties of double d...
متن کاملGiant Resonances from Tdhf
It is well-known that the Random Phase Approximation (RPA) is equivalent to Time-Dependent Hartree-Fock (TDHF) to first order in the density fluctuations from the static Hartree-Fock ground state. Therefore either approach may be used to calculate giant resonance states in nuclei. Historically, the RPA approach has been more popular, particularly working directly in the response function formal...
متن کامل