Probability flux and rectangular-barrier tunnelling
A real one-dimensional potential conserves probability current.
Key knowledge
A real one-dimensional potential conserves probability current. For a rectangular barrier of height V₀ and width a with equal zero-potential exterior regions and 0<E<V₀, the transmitted flux fraction is [1+V₀² sinh²(κa)/(4E(V₀−E))]⁻¹, κ=√[2m(V₀−E)]/ħ; reflection and transmission fractions sum to one.
Values and equations
j=(ħ/m)Im(ψ*∂ψ/∂x); T=[1+V₀²sinh²(κa)/(4E(V₀−E))]⁻¹; R+T=1
- j
- Probability flux for a normalized 1D state s⁻¹
- ψ
- Position amplitude m⁻¹ᐟ²
- ħ
- Reduced Planck constant J s
- m
- Particle mass kg
- x,a
- Position and barrier width m
- E,V₀
- Incident energy and barrier height J
- κ
- Evanescent wavenumber m⁻¹
- T,R
- Transmission and reflection flux fractions
Conditions and scope
- Stationary elastic scattering, constant m>0, a>0, no absorption, and an incoming wave from one side.
- Match ψ and its first derivative at finite potential steps; unequal exterior velocities require a flux ratio, not just squared amplitude.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Quantum Mechanics (2010): Square potential barrier: Equations 316–319, 330–336; the equal-speed flux normalization and sub-barrier continuation.
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Entry details
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- physics-barrier-tunnelling
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