UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2009 Meeting


Section: Nuclear and Elementary Particles Physics


Title:
An improved semi-classical nuclear billiard model for the decay widths of Isoscalar Giant Monopole Resonances


Authors:
Cristian C. BORDEIANU*, Daniel FELEA **, Calin BESLIU*, Alexandru JIPA*, Valentin GROSSU*, Tiberiu ESANU*


Affiliation:
* University of Bucharest, Faculty of Physics, Bucharest-Magurele, P.O. Box MG 11, 077125, Romania

** Institute of Space Sciences, Laboratory of Space Research, Bucharest-Magurele, P.O. Box MG 23, 077125, Romania


E-mail
cristian.bordeianu@brahms.fizica.unibuc.ro


Keywords:
nuclear multifragmentation, isoscalar giant monopole resonances, power spectrum, decay width


Abstract:
We consider several interacting nucleons moving in 2D Woods–Saxon type potential wells and hitting the vibrating surface. This nonlinear classical model was used to calculate the decay widths of Isoscalar Giant Monopole Resonances in the spherical nuclei 208 Pb, 144 Sm, 116 Sn and 90 Zr. It was proved that despite its simplicity and its purely classical nature, the model reproduces the trend of the experimental data which show that with increasing mass number the decay width decreases. We improved the model by using a 3D Woods–Saxon type potential and by introduced some quantum ingredients. Thus, the Hamiltonian takes into account both, the spin and isospin degrees of freedom of the nucleons. The interaction potential includes the Coulomb potential and the One Pion Exchange Potential with tensor term. The numerical simulation is based on the solutions of the Hamilton equations which was solved using an algorithm of Runge–Kutta type (order 4–5) having an optimized step size, taking into account that the absolute error for each variable is less than 10^−6. Total energy is conserved with high accuracy, i.e. approx. 10^−6 in absolute value. We analyze the chaotic behavior of the nonlinear dynamics system using the power spectrum.