Energy Levels According To Second-Order Perturbation Theory

In summary, the conversation discusses using second-order perturbation theory to find the new energy levels when given a Hamiltonian matrix and unperturbed wave functions. However, the exact method for obtaining the unperturbed energies and wave functions is not clear and the person is seeking help.
  • #1
JordanGo
73
0

Homework Statement



If E1≠E2≠E3, what are the new energy levels according to the second-order perturbation theory?


Homework Equations



H' =
α(0 1 0)
(1 0 1)
(0 1 0)

ψ1=
(1)
(0)
(0)
ψ2=
(0)
(1)
(0)
ψ3=
(0)
(0)
(1)

Second order perturbation theory:
[itex] E^{o}_{n}^{2}=\sum(<\Psi_{n}^{o}|H'|\Psi_{o}^{0}>)^{2}/(E_{0}-E_{n})[/itex]

The Attempt at a Solution


I do not know how to obtain the energies of the unperturbed state, nor the functions ψ, can someone help me?
 
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  • #2
JordanGo said:

Homework Statement



If E1≠E2≠E3, what are the new energy levels according to the second-order perturbation theory?


Homework Equations



H' =
α(0 1 0)
(1 0 1)
(0 1 0)

ψ1=
(1)
(0)
(0)
ψ2=
(0)
(1)
(0)
ψ3=
(0)
(0)
(1)

Second order perturbation theory:
[itex] E^{o}_{n}^{2}=\sum(<\Psi_{n}^{o}|H'|\Psi_{o}^{0}>)^{2}/(E_{0}-E_{n})[/itex]

The Attempt at a Solution


I do not know how to obtain the energies of the unperturbed state, nor the functions ψ, can someone help me?

Can you post the entire problem statement as it was given to you, verbatim (word for word)? It makes no sense to ask for the "new" energy levels without first giving some indication of what the "old" ones are, either directly, or with some context.
 

What is second-order perturbation theory?

Second-order perturbation theory is a mathematical method used in quantum mechanics to calculate the energy levels of a system that cannot be solved exactly. It takes into account small perturbations or disturbances to the system and calculates the effect on the energy levels.

How does second-order perturbation theory differ from first-order perturbation theory?

First-order perturbation theory only takes into account the first-order effects of perturbations on the energy levels, while second-order perturbation theory considers both first and second-order effects. This makes it a more accurate method for calculating energy levels.

What is the significance of energy levels in second-order perturbation theory?

The energy levels calculated using second-order perturbation theory can provide important information about the stability and behavior of a quantum system. They can also help predict the outcomes of different experiments and observations.

What are the limitations of second-order perturbation theory?

Second-order perturbation theory is only accurate for small perturbations to a system. If the perturbations are too large, the results may not be reliable. It also does not take into account higher-order effects, which may be necessary for more precise calculations.

What types of systems can be analyzed using second-order perturbation theory?

Second-order perturbation theory can be applied to any quantum system that cannot be solved exactly, such as atoms, molecules, and solids. It is also used in many areas of physics, including nuclear physics, solid-state physics, and quantum chemistry.

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