XLG-MQT, Paper X: Essence of Electronic Transition — Kuiquark Medium Extrusion Oscillation and Xu-Ratio Hierarchical Quantization System

Conventional atomic spectroscopy has been successfully described by empirical formulas and quantum energy-level models. Yet these approaches have not provided a physical mechanism for why transitions occur, why spectra are discretized, or why saturation absorption and element-specific spectral selectivity universally emerge. All quantization in orthodox atomic models originates from mathematical quantization rules rather than inherent microscopic structural constraints of physical media. Based on the fundamental axioms of the Kuiquark sea medium system and the original Xu Ratio theory proposed by Lingguang Xu, this paper completely abandons the artificial quantum energy-level hypothesis. It establishes a medium-based mechanical paradigm for atomic spectral emission and absorption, demonstrating that atomic spectra are not caused by electronic orbital jumps or energy-level collapse, but by extrusion, saturated elastic energy storage and oscillatory rebound release of the atomic semi-free Kuiquark medium. This work defines a discrete hierarchical k-order layer structure of atomic Kuiquark spheres, forming a dual constraint system of photon helix geometric matching and medium elastic energy storage quantization. The vacuum Xu Ratio is fixed as Λ_Xu = π/2, deriving the unique photon helix diameter relation D = 0.385λ. The proposed Xu-Ratio hierarchical quantization system perfectly reproduces the classic Balmer series and helium spectral data with precise numerical coincidence. This paper physically explains long-standing unsolved problems in traditional atomic optics, including spectral discreteness, saturated absorption effect, and atomic element spectral selectivity. It fundamentally replaces the empirical quantum-level formalism with a self-consistent medium mechanical model, realizing a closed physical explanation for microscopic atomic transition quantization.