A theoretical investigation of the bound states and resonances in the N Delta system

Belyaev, V.B.; Möller, K.; Simonov, Yu. A.

doi:10.1088/0305-4616/5/8/010

Cited by 15 publications

(22 citation statements)

References 17 publications

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“…It was shown that QPM provides a very good description of the experimental data in the GDR region [102] (see, Fig. 30), while theoretical calculations at higher excitation energies which account for contributions from the single-phonon GDR and GQR iv essentially underestimated the experimental cross section [103]. The experimental cross sections above 17 MeV are shown in Fig.…”

Section: One-step Excitation Of Two-phonon States In the Energy Regiomentioning

confidence: 91%

“…For 208 Pb photoexcitation cross sections are known from experimental studies in (γ, n) reactions up to the excitation energy about 25 MeV [102,103]. It was shown that QPM provides a very good description of the experimental data in the GDR region [102] (see, Fig.…”

Section: One-step Excitation Of Two-phonon States In the Energy Regiomentioning

confidence: 99%

“…The contribution to the total cross section of the GQR iv (short-dashed curve), the high energy tail of GDR (long-dashed curve), and their sum (squared curve), are taken from Ref. [103]. The curve with triangles represents the contribution of the direct excitation of the two-phonon states from our present studies.…”

Section: One-step Excitation Of Two-phonon States In the Energy Regiomentioning

confidence: 99%

“…Taking into account that the reaction amplitude has very weak energy dependence and that mixing of different RPA phonons in the GDR wave function does not change the total strength [115], the total cross sections of the GDR and DGDR excitation in RHIC will be also conserved. [103]. The long-dashed curve is the high energy tail of the GDR, the short-dashed curve is the GQR iv and the curve with squares is their sum.…”

Section: The Dgdr In Deformed Nucleimentioning

confidence: 99%

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Microscopic studies on two-phonon giant resonances

1999

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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 attention in this review is paid to double giant dipole resonances (DGDR) which are observed in relativistic heavy ion collisions with very large cross sections. A great experimental and theoretical effort is underway to understand the reaction mechanism which leads to the excitation of these states in nuclei, as well as the better microscopic understanding of their properties. The Coulomb mechanism of the excitation of single and double giant resonances in heavy ion collision at different projectile energies is discussed in details. A contribution of the nuclear excitation to the total cross section of the reaction is also considered. The Coulomb excitation of double resonances is described within both, the second-order perturbation theory approach and in coupled-channels calculation. The properties of single and double resonances are considered within the phenomenologic harmonic vibrator model and microscopic quasiparticle-RPA approach. For the last we use the Quasiparticle-Phonon Model (QPM) the basic ideas and formalism of which are presented. The QPM predictions of the DGDR properties (energy centroids, widths, strength distributions, anharmonicities and excitation cross sections) are compared to predictions of harmonic vibrator model, results of other microscopic calculations and experimental data available. : 24.30.Cz, 25.70.De, Pacs

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Section: One-step Excitation Of Two-phonon States In the Energy Regiomentioning

confidence: 91%

Section: One-step Excitation Of Two-phonon States In the Energy Regiomentioning

confidence: 99%

Section: One-step Excitation Of Two-phonon States In the Energy Regiomentioning

confidence: 99%

Section: The Dgdr In Deformed Nucleimentioning

confidence: 99%

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Microscopic studies on two-phonon giant resonances

1999

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“…For 208 Pb photoexcitation cross sections are known from experimental studies in (γ, n) reactions up to the excitation energy about 25 MeV [7,8]. It was shown that QPM provides a very good description of the experimental data in the GDR region [7], while theoretical calculations at higher excitation energies which account for contributions from the single-phonon GDR and GQR iv essentially underestimated the experimental cross section [8]. The experimental cross sections above 17 MeV are shown in Fig.…”

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confidence: 99%

Two-Phonon Background for the Double Giant Resonance

Ponomarev

Bertulani

1997

Phys. Rev. Lett.

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The direct excitation of a "sea" of two-phonon configurations above 15 MeV from the ground state is considered. It is concluded that these configurations form a flat physical background in photoexcitation cross sections and Coulomb excitation in heavy ion reactions at relativistic energies. The contribution of the background to the total cross section in Coulomb excitation of 208 Pb in the double giant dipole resonance (DGDR) energy region is about 15%. It should be considered while drawing conclusions on anharmonicity effects for the DGDR. [S0031-9007(97)04579-1] PACS numbers: 24.30.Cz, 25.70.De, One of the most exciting features of the recently discovered double giant dipole resonance (DGDR) is the absolute value of its excitation cross section in relativistic heavy ion collisions. These values were extracted from total cross sections by separating a contribution arising from the excitation of the single giant dipole resonance (GDR) and of the giant quadrupole resonance (GQR) and were found to be enhanced by factors of the order of 2-3 for 136 Xe [1] and 197 Au [2] as compared to any theoretical calculations available. Although for 208 Pb [3] the experiment-theory correspondence is much better, an enhancement of 1.33(16) is still observed relative to the harmonic approximation.At the present time we have an experimental proof [3] that Coulomb excitation of the DGDR in relativistic heavy ion collisions occurs in a two-step process. The DGDR states are embedded in a sea of other two-phonon states. In this paper we consider the sea contribution to the total cross sections. It will be concluded that numerous twophonon states, other than ͓GDR ≠ GDR͔ ones, excited in one-step processes form a physical background in the DGDR energy region which has to be taken into account in the analysis of experimental data.The first investigation of the direct excitation of twophonon states at high energies from the ground state was done in Refs. [4,5]. The main purpose of these papers was to look for resonance structures in photoexcitation cross sections related to the excitation of rather selected two-phonon configurations. Although in Ref. [5] it was pointed out that ͓GDR ≠ GQR͔ 1 2 and ͓GDR ≠ 2 1 1 ͔ 1 2 configurations were not the only ones (among many different two-phonon ͓1 2 ≠ 2 1 ͔ 1 2 states) to determine the total cross section, two-phonon 1 2 configurations made of phonons of other multipolarities were omitted in the calculation.While dealing with electromagnetic, or with Coulomb excitations from a 0 1 ground state, prime attention has to be paid to the final states with the total angular momentum and parity J p 1 2 . Making use of the formalism presented in Ref.[5] we have calculated first the cross section for the photoexcitation of two-phonon states ͓l p 1

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