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# Hamiltonian Spin

Please assist me in solving the following problems:

Let's consider an ion (in an effective spin state corresponding to s = 1) at a crystal lattice site. As for the effective potential seen by the ion, assume spin Hamiltonian of the form:

H = alpha*S^2_z + beta*(S^2_z - S^2_y)

where alpha and beta are some real constants and |alpha| >> |beta|

a. Choosing the three independent eigenstates of S_2 (corresponding to s = 1) as basis, express H_0 = alpha*S^2_z (unperturbed Hamiltonian) and H' = beta*(S^2_z - S^2_y) (perturbation) by suitable 3 x 3 matrices.

b. For the full Hamiltonian H = H_0 + H', obtain the energy eigenvalues and the corresponding eigenstates which are correct up to 1st-order in beta.

(see attachment for the properly formatted questions)

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#### Solution Preview

Please see the attachment for full solutions.

a.
H_0 = alpha*S^2_z = alphah^2 1 0 0
...

#### Solution Summary

This solution provides a step-by-step process for solving physics problems involving perturbation of a spin Hamiltonian for a quantum mechanical system.

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