1. Romualdo de Souza Nuclear Chemistry- Studying the Behavior of Microscopic Droplets I.General Overview (What & Why) II.Particle Accelerator Labs (Where) III.Experimental Tools (How) IV.Experimental Results V.Outlook (RIA) VI. Other Physical Chemistry at IUB

2. Romualdo de Souza I. General Overview Nuclei behave like microscopic drops of liquid (fairly incompressible yet deformable). Nuclei are small (R= 1-10 x 10 -15 m);10 4 times smaller than an atom; requires measuring instruments of a comparable size to measure them e.g. other nuclei Nuclei are positively charged so one has to overcome the mutual repulsion between two nuclei (Coulomb repulsion) i.e. Particle accelerators are required. Why study nuclei? Necessary to understand the formation of the elements – nucleosynthesis Important in understanding the properties of astrophysical objects such as neutron stars ( a giant nucleus with a radius of ~ 0.6 km)  nuclear equation-of-state. Important in understanding the thermodynamic properties of small, finite systems (strong ties to the study of atomic clusters). Basic facts about nuclei

3. Romualdo de Souza Nucleosynthesis Fe is the most tightly bound nucleus  Fusion of lighter nuclei releases energy  Fission of heavier nuclei releases energy How are heavier nuclei formed if they are not at the thermodynamic minimum ? Supernova explosions

4. Romualdo de Souza Nuclear Equation-of-state In order to understand supernova explosions, neutron stars, and the behavior of nuclei we need to understand the nuclear equation-of-state. Nuclei within the spinodal region are unstable against density fluctuations and disintegrate into many fragments. Nuclear matter at high excitation is prepared by colliding two nuclei.

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6. Collision of a nucleus with a light-ion (Z 2) converts kinetic energy of relative motion into intrinsic excitation i.e. heats the nucleus. From the debris – the fragmentation pattern we need to determine what happened identity of all the particles number of clusters (Z>2) number of light particles Z=1,2 energy of all the particles angles of all the particles Reconstructing a collision

7. Particle accelerators around the U.S. Brookhaven National Laboratory Oakridge National Laboratory TAMU Cyclotron Facility Lawrence Berkeley National Laboratory I.U. Cyclotron Facility

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9. Strongly Damped Collision Strongly damped + neck emission and re-absorption Strongly Damped + neck emission Collisions of Mercury Drops * Plateau-Rayleigh instability Liquid cylinder of length radius R is unstable against wavelengths > 2  R * Thanks to G. Poggi Unstable shapes subject to Plateau-Rayleigh instabilities may be formed due to destabilizing forces. Coulomb repulsion Angular momentum

10. Romualdo de Souza Unit Z resolution from Z=2 to Z=45 Energy is essentially linear with Z Since A  Z and E  Av 2 This means the velocity is essentially constant. Cold spectator fragments Abrasion-Ablation model Hot participant zone Characterize collision by looking at the forward going fragment

11. Romualdo de Souza Cold spectator fragments Abrasion-Ablation model Hot participant zone Plateau-Rayleigh instability little or no velocity damping of projectile-like fragment (PLF) limited mixing of protons and neutrons from projectile and target geometry (impact parameter) governs breakup—volume instability (T,  ) breakup is a surface instability deformation/stretching are the governing factors

12. Romualdo de Souza Particle identification through the interaction of radiation with matter Large Area Silicon Strip Array (LASSA) Incident charged particle 65  m Si 500  m Si 6cm CsI(Tl) Photodiodes

13. Romualdo de Souza Two dimensional  E-E spectrum provides Z,A identification LASSA provides isotopic resolution for Z  9 Si-Si identification Si-CsI(Tl) identification

14. Romualdo de Souza Experimental Setup LASSA 9 telescope array (7°  lab  58°) Si-CsI Ring Counter (2.1°  lab  4.2°) Miniball/Miniwall 4  array Measure: Number of charged particles in each collision (N c ) Number of clusters/IMFs in each collision (N IMF ) Z,E,  of all particles detected Z,A,E,  of all particles detected in LASSA BEAM Target foil 114,106 Cd + 98,92 Mo at E lab /A=50 MeV

15. Romualdo de Souza Velocity of the smaller fragment exceeds velocity of the larger fragment Velocity of the larger fragment exceeds velocity of the smaller fragment Increasing v Two fragments in the Ring Counter

16. Romualdo de Souza Beam velocity Large fragments (projectile-like) are observed at forward angles at near beam velocity. The velocity of the forward going fragment is independent of its size except for the smallest fragments. Smaller fragments (Z<10) are also observed at lower velocities. Z-velocity correlations for fragments in Si-CsI Ring Counter (2.1°  lab  4.2°)

17. Romualdo de Souza Increasing v Charge anti- correlation indicates binary decay of a common parent Quite different decay pattern observed Size of smaller fragment is independent of size of larger fragment Size of smaller fragment is peaked at Z=6 Binary decay of a PLF* Neck fragmentation

18. Romualdo de Souza Velocity of the heavy fragment depends on whether it precedes or trails the lighter fragment and the size of the smaller fragment Velocity of the center of mass of the fragment pair is independent of the velocity order or size of Z L When V H >V L And Z L < 9, Relative velocity of the fragment pair depends on N c  NOT a two stage process. V rel is independent of N c  two stage process. (V rel consistent with fission systematics) Increasing v

19. Romualdo de Souza Dependence of relative yield and relative velocity on the size of the smaller fragment Relative yield is peaked at Z=6 3-5 times more fragment yield for neck fragmentation process as compared to binary decay of PLF* Neck fragmentation is associated with a much larger v rel than binary decay (Coulomb expectation). Where does this extra energy come from?

20. Romualdo de Souza Preliminary Conclusions 1.Neck fragmentation is an effective means for producing fragments in peripheral collisions of projectile and target nuclei. 2.The relative velocity is significantly larger than allowed by Coulomb considerations alone suggesting a stretching of the nuclear matter as the fragments are produced. Interrupted mixing of two finite quantum fluids  Outlook: Study this process by tagging the isospin (N/Z). (N/Z) projectile (N/Z) target (N/Z) light clusters (N/Z) heavy clusters

21. Romualdo de Souza Acknowledgements Indiana University, Bloomington T. Bredeweg B. Davin R. Molina H. Xu Y. Larochelle T. Lefort L. Beaulieu A. Caraley V.E. Viola R.T. deSouza Washington University, St. Louis R.J. Charity L.G. Sobotka Michigan State University T.X. liu X.D. Liu W.G. Lynch R. Shomin W.P. Tan M.B. Tsang A. Vander Molen A. Wagner H.F. Xi C.K. Gelbke

22. G. Martyna J. Zwanziger spontaneous generation of patterns in nature P. Ortoleva D. Clemmer understand and develop materials, with special focus on glassy and partially ordered solids structural and dynamical properties of biochemical and catalytic materials structures of large low- symmetry molecules in the gas phase; protein structure