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Schematic experimental setup

LRA emission during fission was always supposed to be an excellent tool to study the scission process. Schematic experimental setup. Position of the scission point on the potential energy of deformation.

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Schematic experimental setup

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  1. LRA emission during fission was always supposed to be an excellent tool to study the scission process Schematic experimental setup Position of the scission point on the potential energy of deformation

  2. Adiabatic release: a slow thinning of the neck on both sides of the particle. Problem: simultaneous vanishing improbable; if not the nuclear forces from the other side will absorb the particle.

  3. Halpern’s sudden approximation

  4. Double Random Neck-Rupture Hypothesis: during the lifetime of the neck ‘tn’, two independent ruptures occur with equal probabilities. These probabilities are uniformly distributed in space and time: they are the same at each point along the neck and at each moment of time during tn. In addition to tn there are two other times that are important: tr (of the neck rupture) and tabs (of the neck absorption by the fragments) Consequence: if the 2nd ruptures arrives in the interval [tr + tabs - tr] after the 1st rupture the fission is ternary. R=T/B=const*tabs/tn V. Rubchenya, Sov. J. Nucl. Phys. 35 (1982) 334 V. Rubchenya and S. Yavshits, Z. Phys. A329 (1988) 217

  5. Uncertainty Principle • There are different ways to express the quantum mechanical uncertainties: • p = h/2 • E= (p /m )p = (2E/m)1/2 h/(2) = 2.3(E)1/2/ • E t = h/2 • E = 3.3/t • [E] = MeV, [] = fm, [t] = 10-22 sec • Peculiarity: if it has any influence on the emission, we cannot get around it.

  6. Important role of the spectroscopic factor ( alpha clustering)

  7. O. Serot, C. Wagemans et al., in ‘Seminar on Fission’, Pont d’Oye V (2003)

  8. Angular distribution: classical approach based on finite-size trajectory calculations

  9. Effect of the angular resolution on the distribution

  10. Unpublished data from a high angular resolution experiment using the Diogenes detector (J. Theobald, M. Mutterer, et al.)

  11. Angular distribution: quantum approach based on two-dimensional tunneling

  12. Tunneling of a s-state proton is isotropic only for a spherical nucleus; as soon as the nucleus is deformed it escapes perpendicular to the deformation axes. It is not the barrier hight that counts but the spacial distribution of the wave function

  13. Shape of the ridge for different deformations Potential values along the ridge

  14. Square modulus of wave function Time evolution of the angular distribution

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