Elastic optical scattering theorem
For the stated real short-range elastic central-potential problem, the integrated elastic cross section equals σ_el=(4π/k)Im f(0).
Key knowledge
For the stated real short-range elastic central-potential problem, the integrated elastic cross section equals σ_el=(4π/k)Im f(0). This forward-amplitude relation follows flux conservation and the partial-wave expansion, rather than treating scattering as the outgoing spherical intensity alone.
Values and equations
σ_el=(4π/k)Im f(0)
- σ_el
- Integrated elastic cross section m²
- f(0)
- Forward elastic amplitude in unit incident-wave convention m
- k
- Exterior wavenumber m⁻¹
Conditions and scope
- Same unit-incident-amplitude convention as the elastic partial-wave formula, k>0 and a real one-channel potential; the incident–scattered interference must be retained in the forward flux.
- This record proves the elastic case. With inelastic channels the broader optical theorem concerns total extinction/total scattering and needs the corresponding multichannel formulation; no inelastic result is inferred from real δ_l.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Quantum Mechanics (2016): Optical theorem: Equations 10.89–10.90: combine Im[e^(iδ)sinδ]=sin²δ for the real elastic shifts and the integrated cross section. The record does not extend the source's one-channel derivation to unchecked absorption/inelastic cases.
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Entry details
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- physics-optical-scattering-theorem
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- university-core.1
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