1. Email: A.koning@iaea.org
3. The optical model
Prof. Dr. A.J. (Arjan) Koning1,2
1International Atomic Energy Agency, Vienna
2Division of Applied Nuclear Physics, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
EXTEND
European School on Experiment, Theory and Evaluation of Nuclear Data, Uppsala University, Sweden, August 29 - September 2, 2016

2. NC Reaction Tlj THE OPTICAL MODEL Direct (shape) elastic
Direct components
Elastic
Fission
(n,n’), (n,),
(n,), etc…
Inelastic
NC
COMPOUND
NUCLEUS
OPTICAL
MODEL
PRE-EQUILIBRIUM

3. Optical model potential

4. Optical model potential

5. Optical model potential

6. U U = V + iW THE OPTICAL MODEL
Direct interaction of a projectile with a target nucleus considered as a whole
Quantum model  Schrödinger equation
U = V + iW
Complex potential:
Refraction
Absorption

7. THE OPTICAL MODEL The optical model yields : Angular distributions
Transmission coefficients
Integrated cross sections

8. Two types of approaches

9. TWO TYPES OF APPROACHES
Phenomenological
20 adjusted parameters Weak predictive power away from stability Very precise (  1%) Tedious parameter fitting
(Semi-)microscopic
Total cross sections
No adjustable parameters Usable without exp. data Less precise (  5-10 %) Quasi-automated

10. PHENOMENOLOGICAL OPTICAL MODEL
f(r,R,a)= -1
1+exp((r-R)/a)
g(r,R,a) = - df/dr

11. Phenomenological OMP

12. Standard parameterization: 0.001 – 200 MeV
A.J. Koning and J.P. Delaroche, ``Local and global nucleon optical models from 1 keV to 200 MeV'', Nucl. Phys. A713 (2003) 231.

13. Potential depths

14. Local and global OMP
Local OMP: parameter per nuclides Global OMP: mass dependent parametrization, e.g.
KD03 OMP, Nucl. Phys. A713 (2003) 231

15. Neutron total cross sections

16. Neutron total cross sections

17. Neutron non-elastic cross sections

18. Neutron elastic scattering angular distributions

20. No adjustable parameters Based on nuclear structure properties
SEMI-MICROSCOPIC OPTICAL MODEL
No adjustable parameters
Based on nuclear structure properties
 usable for any nucleus
Less precise than the
phenomenological approach

21. Independent of the nucleus
SEMI-MICROSCOPIC OPTICAL MODEL
U(r(r’),E)
r(r’)
Effective
Interaction =
U(r,E)
Optical potential 
r(r)
Radial densities
Depends on the nucleus
Independent of the nucleus

22. Sample 16: optical model for 120Sn
Study impact of changing parameters
talys < input >output (about seconds)
cp totalxs.tot totalxs.org
Edit the input file and add the following line:
rvadjust n 1.05
This means: increase the radius of the real volume potential by 5%
xmgrace totalxs.tot totalxs.org (to see the difference)
TALYS has 250 parameters like this (RT*M)

24. Towards a complete calculation for Cu-65: Optical model
Copy previous sample case for Sn-120, and change into Cu-65
talys < input >output
Retrieve experimental data for total cross sections from EXFOR at IAEA and compare.
Sample case 16 has 4 different sub-cases, for 4 different OMP’s. See what the effect is for Cu-65 (i.e. 4 TALYS curves)