Optical model

The optical model of nuclear physics describes nuclear reactions and the scattering of particles such as nucleons , deuterons or alpha particles on atomic nuclei through a medium potential . In addition to the elastic part of the scattering, this also has an imaginary part to describe the absorption of the projectile particles. This absorption component is the origin of the name, because complex potentials are also used in optics , e.g. B. for the description of the refraction and absorption in a cloudy glass sphere . ${\ displaystyle V (\ mathbf {r})}$ ${\ displaystyle W (\ mathbf {r})}$

For the optical potential

{\ displaystyle U (\ mathbf {r}) = V (\ mathbf {r}) + i \, W (\ mathbf {r})}

becomes common

chosen for a Woods-Saxon potential or another potential used for shell model calculations, usually with a spin-orbit interaction term , ${\ displaystyle V}$

for its derivative , which has its maximum in the area of the steep drop of the Woods-Saxon potential at the core edge. This describes that the absorption of e.g. B. nucleons with energies in the low M eV range due to the Pauli principle is preferably carried out in the area of the outer valence nucleons. ${\ displaystyle W}$ ${\ displaystyle dV (\ mathbf {r}) / d \ mathbf {r}}$

Compound core channels of nuclear reactions can also be taken into account in the optical model . Although the actual compound core can not be described with the simple optical model (with sharp resonances of the Breit-Wigner type ), it is possible to describe the course of the excitation function averaged over many individual resonances .

Due to its adaptability, the optical model has been used very successfully, for example, to describe the elastic scattering of neutrons, alpha particles and deuterons above a few MeV, but also for direct nuclear reactions ( stripping reaction ).

It was originally introduced by Herman Feshbach , Victor Weisskopf and Charles Porter.

literature

H. Feshbach: The Optical Model and Its Justification . In: Annual Review of Nuclear Science . tape 8 , no. 1 , 1958, p. 49-104 , doi : 10.1146 / annurev.ns.08.120158.000405 .
GE Brown : Foundations of the optical model for nuclei and direct interaction . In: Reviews of Modern Physics . Vol. 31, October 1, 1959, pp. 893-919 , doi : 10.1103 / RevModPhys.31.893 .
Peter Edward Hodgson The optical model of elastic scattering . Oxford 1963.
PE Hodgson: The Optical Model of the Nucleon-Nucleus Interaction . In: Annual Review of Nuclear Science . tape 17 , no. 1 , 1967, p. 1–32 , doi : 10.1146 / annurev.ns.17.120167.000245 .
PE Hodgson: The nuclear optical model . In: Reports on Progress in Physics . tape 34 , no. 2 , May 1, 1971, p. 765 , doi : 10.1088 / 0034-4885 / 34/2/306 .
PE Hodgson Nuclear reactions and nuclear structure . Oxford 1971.
PE Hodgson The nucleon optical model . World Scientific 1994.
Bethge et al. a. Nuclear physics . Springer Verlag, pp. 190 ff.
Mayer-Kuckuck nuclear physics . Teubner 1979, p. 263 ff.
Marvin Goldberger , Kenneth Watson Collision Theory . Wiley 1967, Chapter 11.4 (in the Pseudopotential Method chapter , especially p. 798 ff.).
Randall S. Caswell: Nuclear Optical Model Analysis of Neutron Elastic Scattering for Calcium . In: J. Research Natl. Bur. Standards . tape 66 , 1962 ( PDF - Investigation of the elastic scattering of neutrons on calcium nuclei with an optical nucleus model).

Individual evidence

^ Herman Feshbach, Charles E. Porter, Victor F. Weisskopf: The Formation of a Compound Nucleus in Neutron Reactions . In: Physical Review . tape 90 , no. 1 , April 1, 1953, p. 166-167 , doi : 10.1103 / PhysRev.90.166 .

[1] Herman Feshbach, Charles E. Porter, Victor F. Weisskopf: The Formation of a Compound Nucleus in Neutron Reactions . In: Physical Review . tape 90 , no. 1 , April 1, 1953, p. 166-167 , doi : 10.1103 / PhysRev.90.166 .