Nucleated Self-Excitation Pass-Through: The Exchange Account of Two Kinds of Motion and the Pass-Through Spectrum

Transmissive behavior is the most individual signature of a medium, yet engineering has only attenuation coefficients, no mechanism word. Taking the self-excitation structure derived atomically in the companion paper as premise, this paper gives its display in field media: a wave is the self-excitation attenuation relay of a medium field—no spatial displacement; what is transferred is the self-excitation attenuation—and contends that the nucleation divide is an interface, not a wall: four pass-through channels and a bidirectional exchange account. The quantitative pillar is the inverse pass-through spectrum: 23 data points on a unified mean-free-path scale, spanning 21 orders of magnitude; class-level inversion holds strictly under the same-medium constraint; crossings are readings, not counterexamples. Solid-state pass-through gives the electrical isomorph (signal-drift duality, 10^12 speed ratio; superconductivity as the zero-attenuation limit). Closing: attenuation is the first ontological parameter of a medium. Companion data file: inverse pass-through spectrum, 23 rows. [v1.1: AI-review revision—Reading 1 medium-classification corrected (terrestrial pair carries the inversion); MM wording precision (consistency claim); self-contained nucleation definition; dimension interconversions; energy-conservation sentence; Appendix A scale-declaration.] [v1.2: adds §5 the speed spectrum—the conjugate reading of attenuation: complex attenuation (rate and magnitude bound by Kramers–Kronig); the superposition/coupled self-excitation dichotomy with v = c·cos²θ as the mixing-ratio mainstay (dark-state polariton); sections renumbered; references 14–24 added, all crossref-verified.]