One dimensional Coulomb potential

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SUMMARY

The discussion focuses on the one-dimensional Coulomb potential defined as V(x) = -e²/(4πε₀x) for x > 0 and V(x) = ∞ for x ≤ 0. The time-independent Schrödinger equation is derived, leading to the formulation of the ground state wave function. The user approximates the equation for small x, yielding Y = A exp(-me²/(4πε₀ħ²)x). The main concerns raised include the lack of indication that X represents the ground state and the method for determining energy levels, with a suggestion to apply boundary conditions to find the discrete spectrum of solutions.

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ShayanJ
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Consider the potential below:
[itex] V(x)=\left\{ \begin{array}{cc} -\frac{e^2}{4\pi\varepsilon_0 x} &x>0 \\ \infty &x\leq 0 \end{array} \right.[/itex]
The time independent Schrödinger equation becomes:
[itex] \frac{d^2X}{dx^2}=-\frac{2m}{\hbar^2} (E+\frac{e^2}{4\pi\varepsilon_0 x})X[/itex]
I want to find the ground state wave function.This is how I did it:
[itex] Y=\frac{X}{x} \Rightarrow x\frac{d^2Y}{dx^2}+2\frac{dY}{dx}+(\frac{2mE}{\hbar^2}x+\frac{me^2}{2 \pi \varepsilon_0\hbar^2})Y=0[/itex]
But because bound states of this potential are for small x and the ground state has a very very small x,I assumed [itex]x\to 0[/itex] and considered the approximated equation below:
[itex]2\frac{dY}{dx}+\frac{me^2}{2\pi \varepsilon_0 \hbar^2}Y=0[/itex],whose answer is [itex]Y=A\exp{ (-\frac{me^2}{4\pi \varepsilon_0 \hbar^2}x)}[/itex] and so [itex]X=Ax\exp{ (-\frac{me^2}{4\pi \varepsilon_0 \hbar^2}x)}[/itex]
My problems are:
1-There is noting in X that indicates it is the ground state.What should I do about it? Is it an issue at all?
2-How can I find energy levels?
Thanks
 
Last edited:
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You have to solve the exact equation. Finally, applying the boundary condition
X(0) = 0
(because of the unfinite potential step) should deliver the discrete spectrum of solutions.
 

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