1. Global view on fission channels
C. Böckstiegel, S. Steinhäuser, H.-G. Clerc, A. Grewe, A. Heinz, M. de Jong, J. Müller, B. Voss Institut für Kernphysik, TU Darmstadt
A. R. Junghans, A. Kelić, K.-H. Schmidt
GSI, Darmstadt

2. Low-energy fission - Complex structures
- Similar kind of complexity seen in e.g. TKE, mass-dependent neutron yields or gamma-ray multiplicities.

3. Theoretical description
Strutinsky-type calculations of the potential-energy landscape
(e.g. Pashkevich, Möller et al.)
Statistical scission-point models
(e.g. Fong, Wilkins et al.)
Statistical saddle-point models
(e.g. Jensen et al., Duijvestijn et al.)
Dynamical approach based on the solution of Langevin equations of motion
(e.g. Asano et al., Aritomo et al.)
Time-dependent Hartree-Fock calculations with GCM
(e.g. Goutte, Dubray et al.)

4. Experimental difficulties
- Restricted choice of systems
Available targets  stable or long-lived nuclei
Secondary beams  no beams above 238U by fragmentation
Reaction products  limited N/Z range in heavy-ion fusion
- Physical limits on resolution
Z and A resolution difficult at low energies
Scattering in target/detector at low energies (tails in A/TKE
distribution)
- Technical limits on correlations
No experimental information available on A and Z of both fission
fragments simultaneously

5. Use as a test of different theoretical approaches.
What to do?
An empirical overview on the observed structures in low-energy fission. 
Common features behind the large variety of the complex structures seen for the different fissioning systems.
Use as a test of different theoretical approaches.
Same kind of approach done by other authors (e.g. Unik et al, Rochester (1973); Brosa et al, Phys. Rep. (1990); Dematte et al, Nucl. Phys. A (1997); Mulgin et al, Phys. Lett. B (1999)), but for a limited range of N/Z of the fissioning nuclei.

6. Which kind of empirical overview?
- Method of independent fission channels (Super-long, Standard 1, Standard 2) as proposed by e.g. Brosa et al, Phys. Rep. (1990).
Böckstiegel et al, Nucl. Phys. A (2008)
- Analysed data: Z and A distributions measured in EM-induced fission of secondary beams, low-energy particle induced fission and spontaneous fission; for refs. to data see Böckstiegel et al, Nucl. Phys. A (2008)

7. Relative yield of fission channels
- Superlong channel decreases with increasing A
- For given Z of the fissioning system, Standard 1 channel increases with increasing A and Standard 2 decreases.

8. Position of fission channels in A
Standard 1 Standard 2
- For a fixed Z of fissioning system, average positions of Standard 1 and Standard 2 are increasing with increasing mass of the system.

9. Position of fission channels in Z and N
Standard 1 Standard 2
- For both fission channels, position in Z is stable, while position in N increases with A of the fissioning system.

10. Position of fission channels in Z and N
Calculations based on macro-microscopic approach using input from shell model:
N=82 and Z=50 as responsible for Standard 1, and
N=88 as responsible for
Standard 2.
Something beyond shells.

11. Conclusions and outlook
- "Lesson" from the fission-channel study:
The parameters of the fission channels vary in a smooth and
systematic way from Ac to Cf.
Position of St1 and St2 "stable" in Zf and not in Nf.
- Still, we need experimental data with much better quality, especially information on N and Z of both fission fragments simultaneously 
Need for new experimental set-ups,
like e.g. ELISe at FAIR.