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SOTANCP2008 May 13-16 Molecular Resonances in 28 Si+ 28 Si system

E. Uegaki and Y. Abe * Akita Univ. * RCNP, Osaka Univ. SOTANCP2008 May 13-16 Molecular Resonances in 28 Si+ 28 Si system. ○ Nuclear Molecule in heavy ion collisions Structure of the 28 Si- 28 Si Molecule ○ Experiments in Strasbourg :

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SOTANCP2008 May 13-16 Molecular Resonances in 28 Si+ 28 Si system

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  1. E. Uegaki and Y. Abe * Akita Univ. * RCNP, Osaka Univ. SOTANCP2008 May 13-16Molecular Resonancesin 28Si+28Si system ○ Nuclear Molecule inheavy ion collisions Structure of the 28Si-28Si Molecule ○Experiments in Strasbourg : angular distributions, angular correlations and the theoretical results

  2. Angle averaged yields of the 28Si+28Si scatteringR. Betts, et al. PRL47(1981)23 |(Bombarded at Ecm=55.8MeV by StrasbourgGroup)

  3. Introduction • Intermediate resonance observed in heavy-ion scattering • Ecm well above the Coulomb barrier • Correlating in the elastic and inelastic excitations (single and mutual 2+) • Formation of special compound system28Si-28Si Di-nuclear molecule • Many sharp resonances activation of some internal degrees

  4. Coordinate system in 28Si-28Si molecule • Internal degrees of freedom are orientations of symmetry axes of 28Si nuclei and R • Euler angles referring to molecular axis z’

  5. Molecular model • Degrees of freedom: Euler angles referring to molecular axis z’ • Kinetic energy : angular velocities (classical) quantize and describe with total angular mom. J • Nucleus-Nucleus interaction with folding of nucleon-nucleon interactions (DDM3Y) • Stable configurations are expected : Interaction described directly with geometrical configuration

  6. Multi-dimensional energy surfaces with R-beta (beta1=beta2) • Stable (E-min.) configuration is equator-equator one (E-E configuration) Harmonic Approximation at Energy-min. point • Wave Function

  7. Energy curves for interaction potential and effective pot. for J=38 • In E-E configuration • With J=38 Re=7.6fm • Barrier at ~9.5fm R(fm)

  8. On the left : Cross sections of the energy surfaces • On the right : Effective potentials and the wave functions for the ground state and butterfly mode

  9. Normal mode spectrum of 28Si-28Si molecule forJ=38 • Specified by [n, (n+, n-), K, nu]

  10. Wobbling motionK-mixing occurred due to Asymmetric shape of E-E configuration • 24Mg-24Mg (upper) prolate-prolate • 28Si-28Si (lower) oblate-oblate

  11. Asymmetric rotator • Kinetic energy expression

  12. New energy spectrum with Wobbling • (a) K good • (b) Wobbling due to Asymmetry

  13. Strasbourg Exp. at Ecm=55.8MeVFragment Angular Distributions and F-F-γ CorrelationsDis-alignments J=L=38 andcharacteristic “m=0” pattern • quantization axes: a) beam b) normal c) fragments directions

  14. R-matrix theory

  15. Elastic scattering

  16. Theoretical partial decay widths

  17. Partial decay widths with stronger confinements for α-degree

  18. Fragment angular distributions • From upper portion Mutual 2+ Single 2+ and Elastic scattering dσ/dΩ(mb/sr) • Solid lines : Theoretical results with wobbling for the molecular ground state 40 90 115 θｃｍ(degree)

  19. Angular Correlations

  20. Angular correlations for Mutual 2+ decay Ground state wobbling Green : data plot and x2-fit Red : theoretical results good fits are obtained θｃｍ

  21. Mutual 2+ decay For the Butterfly mode Red : wobbling Blue : K=0 θｃｍ

  22. Angular correlations for Single 2+ decay Ground state wobbling Green : data plot and x2-fit Red : theoretical results θｃｍ

  23. Effects from the back ground • Single 2+ decay Red : back ground effects in L=36 aligned configuration Blue : K=0 ground state θｃｍ

  24. Conclusions • With the molecular model, many resonances by the variety of normal modes around the equilibrium (stable E-E configuration) are found, which are expected to be the origin of the sharp resonances observed. • For the Ecm=55.8 MeV resonance, analyses by means of R-matrix theory have been done. The results for the molecular ground state with E-E configuration are in good agreement with exp. The structure is asymmetrically hyper-deformed 28Si-28Si molecule. • In order to explore properties of the many resonance states, further experiments are called for

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