Alpha-decay barrier and bounded Gamow estimate
An alpha channel changes (A,Z) to (A−4,Z−2) plus ⁴He.
Key knowledge
An alpha channel changes (A,Z) to (A−4,Z−2) plus ⁴He. A positive Q supplies relative kinetic energy but does not bypass the daughter–alpha Coulomb barrier. In an s-wave exterior model V(r)=κ/r, the opaque-barrier factor is T≈exp[−2∫_R^(κ/Q)√(2μ(κ/r−Q))dr/ħ]; an effective channel attempt frequency f gives λ_α≈fT, so the rate depends exponentially on the barrier as well as on nuclear structure.
Values and equations
r_c=κ/Q; T≈exp[−(2/ħ)∫_R^r_c√(2μ(κ/r−Q))dr]; λ_α≈fT
- r,r_c,R
- Radius, outer turning radius and inner matching radius m
- κ
- Exterior Coulomb strength J m
- Q
- Channel energy release J
- μ
- Daughter–alpha reduced mass kg
- ħ
- Reduced Planck constant J s
- λ_α,f
- Partial decay rate and effective attempt frequency s⁻¹
- T
- Barrier transmission factor
Conditions and scope
- κ=2(Z−2)e²/(4πε₀), μ is daughter–alpha reduced mass, 0<R<κ/Q and Q>0; nuclear interaction is represented by the inner matching radius and the exterior Coulomb approximation. Use the semiclassical large-action regime.
- f depends on the adopted interior/formation model; this is not a precision lifetime prediction or proof of a permanently preformed alpha cluster. Nonzero orbital angular momentum adds a centrifugal barrier, and alpha decay is not restricted universally to A≥200.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Introduction to Applied Nuclear Physics: chapter 3 (2012): Section 3.3.2, printed pages 42–45: relative reduced mass, exterior Coulomb turning radius, dimensionless barrier integral and effective frequency-times-penetrability model. SI 1/(4πε₀) is restored. Incorrect universal A≥200 claims, arbitrary rectangular-barrier prefactor, and printed decay-rate unit s instead of s⁻¹ are excluded. Quantum Physics III: chapter 3, semiclassical approximation: Section 1, forbidden-region amplitude and opaque-barrier exponent; supplies the controlled exponent, not the nuclear interior prefactor.
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Entry details
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- physics-alpha-decay-tunnelling
- Revision
- university-core.1
- Structured reference record
- University core expansion