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QM simple harmonic oscillator 
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#1
Oct1607, 07:25 PM

P: 1,996

1. The problem statement, all variables and given/known data
If I have a particle in an SHO potential and an electric field, I can represent its potential as: [tex] V(x) = 0.5 * m \omega^2 (x  \frac{qE}{mw^2})^2  \frac{1}{2m}(\frac{qE}{\omega})^2 [/tex] I know the solutions to the TISE: [tex] \hbar^2 /2m \frac{d^2 \psi}{ dx^2} + 0.5 m\omege^2 x^2\psi(x) = E\psi(x) [/tex] (*) (Those are different Es) So, I plug V(x) into the TISE and get: [tex] \hbar^2 /2m \frac{d^2 \psi}{ dx^2} + (0.5 * m \omega^2 (x  \frac{qE}{mw^2})^2  \frac{1}{2m}(\frac{qE}{\omega})^2) \psi(x) = E\psi(x) [/tex] Now, since we only shift and translated the potential, I should be able to find a substitution for x that yields the equation (*) in a new variable y = f(x), right? The problem is, after I move the constant term to the RHS, I cannot find the right substitution. What am I doing wrong? 2. Relevant equations 3. The attempt at a solution 


#2
Oct1607, 11:08 PM

P: 1,996

I think that I can even prove that there is no constant that you can add to x to find a suitable substitution. Something must be wrong here?



#3
Oct1707, 12:07 AM

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PF Gold
P: 11,155

Have you tried the obvious substitution: [itex]\xi = xqE/m\omega ^2 ~[/itex] ?
You can ignore the additive constant and refer all energies relative to that value. 


#4
Oct1707, 02:31 AM

P: 1,996

QM simple harmonic oscillator
Yes, I figured it out. The problem was that I was under the false impression that I had to substitute epsilon for every x in that equation, which does not work.
I realized, however, that you can substitute for psi(x) separately since it is a factor on both sides of the equation. 


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