A Frozen ECSM Electron-Like Packet Molecular Scattering Programme: Validated Domain, Failure Boundary, and the Need for a Physical Screening Descriptor

This paper synthesises the V36C–V42 ECSM molecular electron-scattering programme. The sequence tested whether a frozen ECSM electron-like packet could be confronted with measured molecular elastic electron-scattering angular differential cross-section data without continually retuning the underlying packet. The programme began with direct frozen-packet confrontation, proceeded through empirical target-response extraction, predictive response modelling, cross-target replication, generic model competition, descriptor-constrained closure, and finally third/fourth-target validation. The synthesis result is deliberately bounded. The frozen packet alone is insufficient, but a structured target-response layer repeatedly improves measured molecular scattering predictions. The response layer generalises across methane, sevoflurane, and isoflurane, and the V41 atom-count descriptor law passes a clean same-grid third-target validation on isoflurane. However, trichlorofluoromethane, CCl3F, exposes a heavy-halogen boundary. The frozen V41 atom-count law improves CCl3F strongly relative to bare ECSM, and a V42C descriptor-coupled scale-law repair improves it further, but neither reaches strict recovery. The conclusion is that the ECSM molecular scattering branch has a validated domain and a clear failure boundary. It does not yet provide a universal molecular scattering law. The next required object is a physically derived screening, polarisation, or molecular response-burden descriptor tested prospectively against the CCl3F boundary.