Function slbw_cross_sections_for_range 

pub fn slbw_cross_sections_for_range(
    range: &ResonanceRange,
    energy_ev: f64,
    awr: f64,
    target_spin: f64,
) -> (f64, f64, f64, f64)

Compute SLBW cross-sections for a single resolved resonance range.

Thin wrapper: per L-group, builds the precomputed J-groups once and delegates to slbw_evaluate_with_cached_jgroups. The batch grid path (cross_sections_on_grid) calls the same evaluator with J-groups precomputed once per range, which is how we guarantee batch/per-point bit-exact equivalence.

Returns (total, elastic, capture, fission) in barns.

Panics

Panics if energy_ev is not finite or is non-positive. This is a defensive guard at the public boundary; the Python wrapper and the SAMMY-style dispatcher already validate the energy grid via validate_energy_grid, so this assertion only fires for direct callers (other Rust crates, tests) that bypass the grid check.