Dynamical dipole mode in fusion reactions at 16 MeV/nucleon and beam energy dependence

Journal Article · Sat Aug 15 00:00:00 EDT 2009 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.80.024612· OSTI ID:21293786

Pierroutsakou, D; Boiano, A; Romoli, M ^[1]; Martin, B; Inglima, G; Commara, M La; Parascandolo, C; Sandoli, M ^[1]; Agodi, C; Alba, R; Colonna, M; Coniglione, R; Zoppo, A Del; Maiolino, C; Piattelli, P; Santonocito, D; Sapienza, P ^[2]; Baran, V ^[2]; NIPNE-HH, 077125 Magurele ^[3]; Cardella, G ; Filippo, E De ^[4]

---

1. INFN, Sezione di Napoli, via Cintia, 80125 Napoli (Italy)
2. INFN, Laboratori Nazionali del Sud, via S. Sofia, 95123 Catania (Italy)
3. Romania
4. INFN, Sezione di Catania, 95123 Catania (Italy)

High-energy {gamma} rays and light charged particles from the {sup 36}Ar+{sup 96}Zr and {sup 40}Ar+{sup 92}Zr reactions at E{sub lab}=16 and 15.1 MeV/nucleon, respectively, were measured in coincidence with evaporation residues by means of the MEDEA multidetector array coupled to four parallel plate avalanche counters. The aim of this experiment was to investigate the prompt {gamma} radiation, emitted in the decay of the dynamical dipole mode, in the {approx}16 MeV/nucleon energy range and to map its beam energy dependence, comparing the present results with our previous ones obtained at lower energies. The studied reactions populate, through entrance channels having different charge asymmetries, a compound nucleus in the region of Ce under the same conditions of excitation energy and spin. Light charged particle energy spectra were used to pin down the average excitation energy and the average mass of the system. By studying the {gamma}-ray spectra of the charge symmetric reaction {sup 40}Ar+{sup 92}Zr, the statistical giant dipole resonance (GDR) parameters and angular distribution were extracted, and a comparison of the linearized 90 deg. {gamma}-ray spectra of the two reactions revealed a 12% extra yield in the GDR energy region for the more charge asymmetric system. The center-of-mass angular distribution data of this extra {gamma} yield, compatible with a dipole oscillating along the symmetry axis of the dinuclear system, support its dynamical nature. The experimental findings are compared with theoretical predictions performed within a Boltzmann-Nordheim-Vlasov transport model and based on a collective bremsstrahlung analysis of the entrance channel reaction dynamics. An interesting sensitivity to the symmetry term of the equation of state and to in-medium effects on nucleon-nucleon (nn) cross sections is finally discussed.

• OSTI ID: 21293786
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 80, Issue 2; Other Information: DOI: 10.1103/PhysRevC.80.024612; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR DISTRIBUTION
ARGON 36 TARGET
ARGON 40 TARGET
ASYMMETRY
BREMSSTRAHLUNG
CENTER-OF-MASS SYSTEM
CHARGED PARTICLES
COINCIDENCE METHODS
COMPARATIVE EVALUATIONS
COMPOUND NUCLEI
CROSS SECTIONS
DIPOLES
ENERGY DEPENDENCE
ENERGY SPECTRA
EQUATIONS OF STATE
EXCITATION
GAMMA DECAY
GAMMA RADIATION
GAMMA SPECTRA
GIANT RESONANCE
MASS
MEV RANGE 10-100
NUCLEONS
SENSITIVITY
SPIN
SYMMETRY
TRANSPORT THEORY
ZIRCONIUM 92
ZIRCONIUM 96