How to Solve Quantum Mechanics Problems Using Commutation Relations

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http://ejokeimg.pchome.com.tw/see-post.html?Flow_No=30201&cat=47&rank="

I try using the commutation relation of the position operator and the Hamiltonian, but failed.:bugeye::bugeye:

Thanks for your kindly help!
 
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By the way, I don't know how to show the pics directly, sorry about that.
 
Multiply the left hand side by the energy denominator. Insert the hamiltonian operator. The commutator trick should then work.
 
StatMechGuy said:
Multiply the left hand side by the energy denominator. Insert the hamiltonian operator. The commutator trick should then work.


Thanks for your reply.^^ You mean like this?
But it's not the original equation. I know that the commutator of position and Hamiltonian is equal to velocity multiplies by
i and hbar(positive or negative sign added). But what I want to know is how to transform the position operator "itself" into the "velocity form" in the first pic I posted. Or my procedure is simply incorrect?
 
Attachments
  • Equation: (E_j - E_i) <ψ_i| r |ψ_j> = -iħ <ψ_i| ∂/∂t r |ψ_j>, relating matrix elements of position between energy eigenstates to a time derivative.
    rtov1.JPG
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  • Handwritten-style equation: <ψi| r̂ H |ψj> − <ψi| H r̂ |ψj> = −<ψi| iħ ∂/∂t r̂ |ψj>, relating matrix elements of the position operator and Hamiltonian to the time derivative of position.
    rtov2.JPG
    3.4 KB · Views: 479
  • Equation: <ψi| [r̂, H] |ψj> = -<ψi| iħ ∂/∂t r̂ |ψj>, relating a commutator of position and Hamiltonian to a time derivative of position between bra and ket states.
    rtov3.JPG
    2.6 KB · Views: 548
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Ooooooooooops, I got through it, thanks for you help!
You are right! No further questions at all...