Finite well bound-state matching
For V(x)=−V₀ inside |x|<a/2 and zero outside, bound states have −V₀<E<0.
Key knowledge
For V(x)=−V₀ inside |x|<a/2 and zero outside, bound states have −V₀<E<0. With q=√[2m(E+V₀)]/ħ and κ=√(−2mE)/ħ, continuity of ψ and ψ′ gives κ=q tan(qa/2) for even states and κ=−q cot(qa/2) for odd states. Exterior amplitudes decay exponentially; the one-dimensional attractive well has at least one even bound state.
Values and equations
κ=q tan(qa/2) (even); κ=−q cot(qa/2) (odd); q²+κ²=2mV₀/ħ²
- q,κ
- Interior oscillation/exterior decay constants m⁻¹
- a
- Well width m
- m
- Particle mass kg
- E,V₀
- Eigenenergy and well depth J
- ħ
- Reduced Planck constant J s
Conditions and scope
- One nonrelativistic particle with constant positive mass, V₀>0 and a>0; finite step discontinuities without delta-function terms.
- The interior and exterior energy zeros follow the displayed convention; an odd-state threshold is not a threshold for existence of every bound state.
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 well: Equations 372, 375–387: even/odd states, decaying exterior, derivative matching and shallow-well even state. Excludes the figure-caption claim that a square root takes value zero beyond its real domain.
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Entry details
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