- #1
naharrison
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Homework Statement
Consider two non-identical, non-interacting particles of mass M that are constrained to move on a circle of radius R. Write down the Schrodinger equation for this problem and find the eigenfunctions and energy levels of this system.
Homework Equations
(see below)
The Attempt at a Solution
I started by defining a coordinate system where the circle is centered at the origin of the x-y plane (z = 0). The particles don't interact and there is no external potential so V = 0. Also, using spherical coordinates, [tex] r = R, \ \theta = \frac{\pi}{2} [/tex] . I then wrote down the Schrodinger equation:
[tex] [-\frac{\hbar^2}{2m_{1}}\nabla^{2}_{1} - \frac{\hbar^2}{2m_{2}}\nabla^{2}_{2} + V]\psi(r,\theta,\phi) = E\psi(r,\theta,\phi) [/tex]
The Laplacian in spherical coordinates is:
[tex] \frac{\partial^2}{\partial r^2} + \frac{2}{r}\frac{\partial}{\partial r} + \frac{1}{r^2}[\frac{1}{sin\theta}\frac{\partial}{\partial\theta}(sin\theta\frac{\partial}{\partial\theta}) + \frac{1}{sin^2\theta}\frac{\partial^2}{\partial \phi^2}] [/tex]
Since r and theta are fixed, the Schrodinger equation reduces to:
[tex] \frac{1}{2}(\frac{\hbar}{R})^2(m_1 + m_2)\frac{\partial^2\psi}{\partial\phi^2} + E\psi = 0 [/tex]
letting [tex] a = \sqrt{\frac{2R^2E}{\hbar^2(m_1 + m_2)}} [/tex] the solution of the Schrodinger equation is:
[tex] \psi = Ae^{a\phi} + Be^{-a\phi} [/tex]
This is where I get stuck. I assume the next step is to apply boundary conditions which will then give the energy levels. How do you do this in this situation? I tried:
[tex] \psi(0) = \psi(2\pi) [/tex]
[tex] \frac{\partial\psi(0)}{\partial\phi} = \frac{\partial\psi(2\pi)}{\partial\phi} [/tex]
but the results didn't make any sense. Any thoughts? Thank you in advance!