Module coulomb 

Coulomb wave functions via Steed’s continued-fraction method.

Provides F_L(η,ρ), G_L(η,ρ), F’_L, G’_L and the derived penetrability P_L, shift S_L, and phase φ_L for charged-particle exit channels in LRF=7 (R-Matrix Limited) cross-section calculations.

SAMMY References

• coulomb/mrml08.f90 Coulfg — Steed’s CF1+CF2 algorithm (Barnett 1981)
• rml/mrml07.f Pgh subroutine — if (Zeta.NE.Zero) branch
• Barnett, CPC 21 (1981) 297–314

Limit η → 0

When η = 0, F_0 = sin ρ, G_0 = cos ρ, reproducing hard-sphere (Blatt-Weisskopf) penetrabilities from penetrability.rs.

Functions

coulomb_penetrability

Coulomb penetrability P_L = ρ / (F_L² + G_L²).

coulomb_wave_functions

Coulomb wave functions (F_L, G_L, F’_L, G’_L) via Steed’s CF1+CF2 method.

sommerfeld_eta

Sommerfeld parameter η for a Coulomb channel.