6.2 Spontaneous Emission and Where Light Comes From

Home ／ Chapter 6: Quantum Domain

Unified Mechanism: Stockpiled Energy → Packet Formation → Release

Any episode of “light emission” reduces to three steps:

• Store energy (build inventory). Atoms, molecules, solids, and plasmas hold energy in tighter or looser tension configurations. Heating, electric acceleration, beam collisions, or chemical reactions lift the configuration; the system parks energy as tension inventory (excited, accelerated, or ionized states).
• Form a packet (cross the release threshold). Internal phase drifts into a “ready-to-release” band; background ripples of the Energy Sea give a nudge; the local system crosses a release gate and packs a coherent envelope of tension—a packet of light that propagates as a wave. Crucial point: packet formation is thresholded. Below threshold nothing “seeps out”; at threshold a whole packet forms—one source of light’s discreteness (source-side quantization).
• Emit and propagate (clear the path threshold). Whether the packet “goes far” depends on the path threshold: coherence quality, a frequency inside a transparent window, and matched orientation/channel. Satisfy them → long range; otherwise, absorption, thermalization, or scattering near the source. Encountering a receiver (electron, molecule, detector pixel) adds a closure threshold: only after crossing it does absorption or emission count. Because the gate is indivisible, detection also occurs one packet at a time (receiver-side quantization).

Summary: the formation threshold sets how emission happens; the path threshold determines how far packets travel; the closure threshold sets how absorption/secondary emission happens. This threshold chain welds wave propagation and particle-like bookkeeping into one picture.

Why Emission Can Be “Spontaneous”

• Excited states are costly: lifted configurations are tighter in the tension sense and tend to relax once phase nears a releasable band.
• The Sea always has “background noise” (Tension Background Noise, TBN): broadband micro-perturbations tap the system constantly.
• A knock at the gate triggers release: when phase is ready and noise nudges, the system crosses the release gate and ejects a light packet.
• Stimulated emission simply lowers the gate: an in-phase external wave reduces the release threshold; many releases phase-lock and depart in formation (laser).
• Spontaneous emission is thus excited state + background noise + release threshold acting in concert—not magic.

Main “Origins of Light” (Grouped by Physical Cause)

Each follows store → form → release; what varies is how inventory builds, how the threshold is crossed, and which channel carries the packet.

1. Line Emission (atomic/molecular level drops)
   • Inventory: electron configurations are lifted (excitation, capture after ionization).
   • Formation: phase enters the releasable band; Sea noise nudges across threshold; a coherent packet forms; the frequency locks to the internal cadence.
   • Release: nearly isotropic; linewidth set by lifetime (shorter → broader) and environmental dephasing (collisions, field roughness).
   • Delayed light (fluorescence/phosphorescence): metastable traps keep the gate closed longer, producing delays or multi-channel competition before release.
2. Thermal Radiation (blackbody/quasi-blackbody)
   • Inventory: myriad micro-processes shuttle energy in the surface region.
   • Formation: countless small packets are repeatedly reprocessed at rough boundaries and smoked to black, averaging discrete shares statistically.
   • Release: spectrum set by temperature; directions near-isotropic; weak coherence, yet emissivity and polarization still depend on surface tension/roughness.
3. Radiation from Accelerated Charges (synchrotron/curvature, bremsstrahlung)
   • Synchrotron/curvature: charges bend in magnetic fields or curved tracks, continuously forming and shedding packets—strongly directed, strongly polarized, broadband.
   • Bremsstrahlung: rapid deceleration in strong Coulomb fields rewrites local tension abruptly and ejects a broadband packet; strongest in dense/high-Z materials.
4. Recombination Radiation (free electron captured)
   • Inventory: an ion “pocket” captures an electron, relaxing from a tighter to an easier configuration.
   • Formation/Release: the energy difference crosses threshold and a packet is ejected.
   • Signature: clear line series—“neon signs” of nebulae and plasmas.
5. Annihilation Radiation (untying opposite windings)
   • Inventory: counter-oriented, stable windings meet and unwind.
   • Formation/Release: inventory becomes two (or more) counter-propagating packets (narrowband, paired direction), e.g., the classic 0.511 MeV pair.
6. Čerenkov Radiation (phase-velocity cone)
   • Inventory: a charge outruns the medium’s phase velocity.
   • Formation/Release: phase is torn along a cone; blue glow is packed and emitted; the cone angle is set by the medium’s phase velocity.
   • Channel: a special case of path-threshold persistently exceeded in the super-phasic regime.
7. Nonlinear and Mixing Processes (conversion, sum/difference, Raman)
   • Inventory: external optical fields supply energy; medium redistributes via nonlinearity.
   • Formation/Release: with phase-matching and channel alignment, a new-frequency packet is emitted (stimulated or spontaneous); directionality and coherence depend strongly on geometry and material tension.

How Three Observables Arise from the Substructure: Linewidth, Directivity, Coherence

• Linewidth: shorter lifetimes leave less time to “sharpen frequency,” producing broader lines; noisier environments (collisions, rough fields) dephase faster and broaden further.
• Directivity/Polarization: set by near-field geometry plus tension gradients. Free atoms tend to emit nearly isotropically; in magnetic fields, collimated channels, or near interfaces, emission is sculpted into strong directivity and polarization.
• Coherence: a single release is coherent; repeated reprocessing drives toward low coherence (thermal light); stimulated, phase-locked release can push coherence to the limit (laser).

Not Every Disturbance Becomes Light that Travels Far: Path Threshold Filters

• Insufficient coherence: the envelope breaks at birth and cannot travel as a packet.
• Window mismatch: frequency lies in strong-absorption bands and dies near the source.
• Channel mismatch: without a low-impedance corridor or with wrong orientation, energy dissipates quickly.
• Light that travels far must satisfy all three: clean envelope + in-window frequency + channel match.

Alignment with Established Theory

• Einstein A/B coefficients: in EFT, spontaneous probability becomes “background knocks + release threshold,” while stimulated emission is “phase lock + lowered gate.”
• Quantum electrodynamics: treats light as quanta of a field and computes interactions precisely; EFT adds the formation → path → closure material map explaining why discrete, why propagable, and why detectable.
• Classical electrodynamics (“accelerated charges radiate”): in EFT terms, the tension landscape is continually rewritten, yielding continuous packet formation and shedding.

In Summary

• Spontaneous emission = an excited state nudged by background crosses a release threshold and ejects a packet of light.
• Light is one packet at a time because of source-side formation thresholds and receiver-side closure thresholds.
• Where light comes from: lines, thermal emission, synchrotron/curvature, bremsstrahlung, recombination, annihilation, Čerenkov, and nonlinear conversion—all variations on the same three-step recipe.
• Linewidth, directivity, and coherence reflect lifetimes, environment, geometry, and tension.
• Not every disturbance makes far-traveling light: clean packet + correct window + channel match are all required.

In a single line: Light is a packeted wave in the Sea; discreteness comes from thresholds—source sets color, path sculpts form, gate sets capture.