- 81U05 $2$-body potential scattering theory [See also 34E20 for WKB methods]
- 81U10 $n$-body potential scattering theory
- 81U15 Exactly and quasi-solvable systems
- 81U20 $S$-matrix theory, etc.
- 81U30 Dispersion theory, dispersion relations
- 81U40 Inverse scattering problems
- 81U99 None of the above, but in this section