Function cross_sections_for_rml_range 

pub fn cross_sections_for_rml_range(
    rml: &RmlData,
    energy_ev: f64,
) -> (f64, f64, f64, f64)

Compute cross-section contributions from an LRF=7 energy range.

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

Iterates over all spin groups (J,π), sums their contributions. A single RmlWorkspace is allocated once and reused across spin groups.

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.